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Select this Article		An Application of Topological Optimization to Bridge Design B. Briseghella, L. Fenu, C. Lan, E. Mazzarolo, and T. Zordan Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000416 Posted ahead of print 16 May 2012 Full Text: \| Download PDF
	+ -	Show Abstract Currently, structural optimization has become an important tool for structural designers because it allows a better exploitation of material, thus decreasing a structure's self‐weight and saving material costs. Moreover, structural optimization helps the designer to find innovative design solutions and structural forms that not only better exploit material but also give the structure greater aesthetic value from an architectural point of view. In this article, the seismic retrofitting of a bridge originally designed in reinforced concrete is illustrated, showing how lightening the bridge superstructure, rather than reinforcing the already completed foundations and abutments, allowed these latter to resist greater seismic actions as required in the recent update of the Italian Seismic Code. Therefore, besides using the steel‐concrete composite typology, the bridge superstructure was lightened through structural optimization. After having optimized the thickness of webs and flanges, it was necessary to further lighten the bridge superstructure by removing unexploited material from the bottom flange through insertion of large cavities. For this purpose, topology optimization is shown to be a powerful tool that allowed the designer to find that the hole shape was basically elliptic, thus suggesting their regularization as ellipses. Comparisons were made between several design solutions, each characterized by a specific volume reduction of the bottom flange. Identification of the highest performing solutions through computer‐aided procedures led to a weight reduction of 40% with respect to the design solution in reinforced concrete. Retrofitting the already existing foundations and abutments to satisfy the updated provisions of the new Seismic Code was thus avoided by defining an innovative layout of arch bridges with holes in the bottom flange, which has never been used before.

Select this Article		Nondestructive Assessment of a Jetty Bridge Structure Using Impact‐Echo and Shear Wave Techniques N. Dawood, H. Marzouk, A. Hussein, and N. Gillis Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000415 Posted ahead of print 14 May 2012 Full Text: \| Download PDF
	+ -	Show Abstract In the current investigation, non‐destructive testing techniques were applied to evaluate the condition of existing jetty bridge structure. The structure serves as an access point for the loading and unloading of various oil products. The nondestructive strategies included crack opening measurements using the concrete crack microscope; impact‐echo test to measure the depth of the different cracks; and shear wave test to detect various defects inside the concrete girders and prestressed ducts. Two AASHTO girders of the jetty were chosen to carry out the various nondestructive testing. The primary objectives of the tests are to assess the overall general condition of the structure and to provide recommendations that could be used to maintain the jetty for its current usage. The combination of the two nondestructive techniques (impact‐echo and shear wave) enabled inspectors to visualize the extension of the cracks in three dimensions and to specify the location of various regions of deterioration within the structural members with a satisfactory level of efficiency. Repair recommendations for the damaged regions were preformed to maintain safe and economic operation of the Jetty's facilities.

Select this Article		Effects of Pounding and Skewness on Seismic Responses of Typical Multi‐Span Highway Bridges Using Fragility Function Method Yili Huo and Jian Zhang, A. M. ASCE Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000414 Posted ahead of print 14 May 2012 Full Text: \| Download PDF
	+ -	Show Abstract This paper employs the fragility function method to study the effects of pounding and skewness on the seismic behaviors of typical multi‐span reinforced concrete highway bridges. Three dimensional numerical models are built for typical three‐span bridges in California that include nonlinear pier columns, distributed gap elements simulating pounding at both expansion joints and end abutments, and soil‐structure interaction effects. The spatial differences of seismic excitations at different supports due to varied soil profile properties and wave propagation effects etc. are also included. Based on the nonlinear time history analyses using a large set of three‐component earthquake ground motion records, fragility functions are derived and compared for bridges with various structural details, including the location of gaps, deck skew angle and gap size. Although pounding causes significant local damage, the fragility functions show relatively moderate change in damage probability of the entire bridge. When pounding does not happen, skewed bridges outperform straight ones due to their coupled responses. For straight bridges, the pounding has limited effect on bridge level damage and can be negligible. However, pounding results in increased damages of skewed bridges which aggravate with large skew angles. Utilizing fragility functions, the paper clarifies the interactive roles of skewness and pounding for seismic damage probability of multi‐span highway bridges. The findings can provide valuable guidance for future bridge design.

Select this Article		Experimental Evaluation of the Scale of Fluctuation for Spatial Variaility Modelling of Chloride Induced Reinforced Concrete Corrosion A. J. O'Connor and O. Kenshel Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000370 Posted ahead of print 2 May 2012 Full Text: \| Download PDF
	+ -	Show Abstract This paper provides experimentally determined estimates of the scale of fluctuation of the principal variables employed in modelling chloride induced corrosion for reinforced concrete, i.e. the surface chloride content (C_s) and diffusion coefficient (D_app). Estimation of the scale of fluctuation, θ, is based upon analysis of experimental data recorded on a bridge in South East Ireland prior to its extensive rehabilitation in 2007. In determining the scale of fluctuation the paper considers two commonly used methods, i.e. the Maximum Likelihood Method and the autocorrelation Curve Fitting Method. The reliability of both methods is discussed. Introduction of the kriging statistical interpolation method is demonstrated to improve the reliability of the estimates of the scale of fluctuation. The results obtained from the analysis are compared to values proffered by other researchers in the literature.

Select this Article		Evaluating Fire Resistance of Steel Girders in Bridges Venkatesh Kodur, Esam Aziz, and Mahmud Dwaikat Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000412 Posted ahead of print 26 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract In the current practice, no special measures are applied for enhancing structural fire safety of steel bridge girders. Further, there is very limited information and research data in the literature on the fire resistance of structural members in bridges. In this paper the fire response of a steel bridge girder under different conditions is evaluated using the finite element computer program ANSYS. In the analysis, the critical factors that influence fire resistance, namely fire scenario, fire insulation and composite action arising from steel‐concrete interaction is accounted for. Results from numerical studies show that the composite action arising from steel girder‐concrete slab interaction significantly enhances the structural performance (and fire resistance) of a steel bridge girder under fire conditions. Other significant factors that influence fire resistance of steel bridge girder are fire insulation and type of fire scenarios.

Select this Article		Wind Actions on Suspension Bridge Catwalks and Its Mitigations Soon‐Duck Kwon, Ph.D., Hankyu Lee, Seungho Lee, Ph.D., and Jonghwa Kim, Ph.D. Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000410 Posted ahead of print 4 May 2012 Full Text: \| Download PDF
	+ -	Show Abstract In the present study, wind tunnel tests and buffeting analyses were conducted for a catwalk structure of a suspension bridge under turbulent winds. From the wind tunnel tests, it was found that the Reynolds number effects on the aerostatic coefficients were negligible for the catwalk floor systems. Simple design formulae were proposed to estimate the aerostatic coefficients of catwalks with various solidity ratio and angle of attack. The buffeting analysis results revealed that tying the catwalk on an erecting main cable may be an effective structural countermeasure to reduce the lateral displacements of the catwalk. Stay ropes fastening the catwalk and bridge tower were also found to be effective to alleviate the lateral displacements.

Select this Article		Destructive Testing of a Decommissioned Reinforced Concrete Bridge Jianren Zhang, Hui Peng, and C. S. Cai, F. ASCE Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000408 Posted ahead of print 26 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract A destructive field testing of a simply‐supported channel‐beam bridge was carried out to gain insight into the ultimate load‐carrying capacity of existing reinforced concrete bridges. Based on a field inspection and assessment of the material strength, structural damage, and structural degradation before testing, a detailed test program was developed. It was observed from the testing that the field bridge exhibited local nonlinearities due to its beam‐to‐beam bolted connections and initial damages. The failure mode of the tested bridge was the typical flexural failure characterized by yielding of rebars and concrete crushing. Some concrete failures were also observed at the location of bridge bearings. The observed load carrying capacity was much higher than that of the original design of the tested bridge and much more studies are needed to understand the real performance of field bridges.

Select this Article		Shear and Friction Response of Non‐Seismic Laminated Elastomeric Bridge Bearings Subject to Seismic Demands Joshua S. Steelman, S. M. ASCE, Larry A. Fahnestock, P.E., M. ASCE, Evgueni T. Filipov, James M. LaFave, P.E., Jerome F. Hajjar, P.E., F. ASCE, and Douglas A. Foutch, P.E. Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000406 Posted ahead of print 26 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract Laminated elastomeric bridge bearings are commonly employed in areas with low to moderate seismicity, although the applications are typically intended for service‐level considerations such as thermal movements of the bridge superstructure. These components provide a potential source of displacement capacity frequently neglected for seismic design. An experimental program was carried out to evaluate behavioral characteristics and performance of steel‐reinforced, laminated elastomeric bearings, which had not been designed for seismic demands, as primary quasi‐isolation components for seismic events by permitting slip at the interface of bearing and substructure. The rubber at the top of the bearing is vulcanized to a steel plate, which is bolted to the test frame to simulate a connection to the superstructure. At the base of the bearing, the elastomer directly contacts concrete representing the substructure, with no restraint of horizontal motion other than friction. The elastomeric bearings investigated during the experimental program displayed approximately linear elastic response before sliding, with an initial friction coefficient in the range of 0.25 to 0.5 (at a shear strain between 125% and 250%) depending on combinations of bearing size, applied load, and bearing velocity. Friction coefficient decreased as a nonlinear function of imposed vertical load. Maximum elastomer shear strain prior to sliding exhibited nonlinear increases with vertical load, resulting from the influence of the variable friction coefficient. Linear shear moduli were primarily influenced by the maximum shear strain imposed on the bearing, and showed shear stiffness reductions of approximately 40 to 50% following multiple, large displacement slip cycles, compared to 15 to 25% after reaching 50% shear strain. Multiple cycles of large displacement demands resulted in noticeable degradation in friction coefficient over the duration of the tests. However, the bearings possess a high degree of resiliency, considering that the specimens retained load carrying capacity through total cumulative slip travel demands in the range of 3.5–4.5 m (140–180 in.).

Select this Article		Detection of the Presence of Broken Wires in Cable by Acoustic Emission Inspection H. Zejli, L. Gaillet, A. Laksimi, and S. Benmedakhene Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000404 Posted ahead of print 26 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract Safety of suspension or stay cable bridges depends on the durability of their cables; those latter may present a healthy aspect on observable lengths but be damaged in the non visible parts (anchorages). It is important to be able to detect as early as possible the defects affecting them. In this study, the acoustic emission (AE) technique is employed in order to detect the presence and locate of broken wires in anchorage. Allowing a cable vibrate can in induce AE from interwire fretting. The study of the behaviour of a broken wire during bending contributed to the understanding of the origin of the AE, i.e. interwire fretting and to the definition of the most suited bending conditions. For the identification of interwire friction, the main parameters of the acoustic signals are the number of events, their energy and frequency distribution. These parameters are very dependent of roughness, lubrication, contact strength between wire and the recovery length. Several cables were studied with various surface conditions: corroded, dry and oiled.

Select this Article		Corrosion Estimation of a Historic Truss Bridge Using Model Updating Shinae Jang, A. M. ASCE, Jian Li, and Billie F. Spencer, Jr., M. ASCE Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000403 Posted ahead of print 20 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract Bridge structures are valuable national assets for transportation and economy, which should be maintained properly for continuous stable operation. Corrosion is common in steel bridges; severe corrosion may result in significant economic impact and long downtime for retrofit. To date, various corrosion evaluation technologies have been developed such as nondestructive evaluation (NDE) techniques and analytical model updating strategies. Among them, NDE is costly and time consuming for scanning entire bridges. For model updating, few examples on full‐scale bridges with severe corrosion have been reported. In this paper, the corrosion level in a historic steel‐truss bridge is estimated using model updating. Dynamic characteristics of the bridge are identified via a series of short‐term full‐scale experiments. An initial finite element (FE) model of this bridge is then updated to match the field corrosion estimation results. The corrosion levels predicted by the proposed approach were consistent with the results of a visual inspection of this bridge. The results of the model updating routine could be used to monitor the overall corrosion levels in the structure with periodic inspection over time.

Select this Article		Improved Serviceability Criteria for Steel Girder Bridges Michael G. Barker, Ph.D., P.E. and Karl E. Barth, Ph.D. Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000402 Posted ahead of print 20 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract Current AASHTO LRFD Bridge Design Specifications Service I deflection limits are in place with the purpose to prevent deformation‐induced structural damage and psychological user‐discomfort from excess bridge vibration. Previous research has shown that deflection criterion alone is insufficient in controlling excess bridge vibrations and structural deterioration of the concrete deck. Previous research shows that natural frequency criteria better controls excess vibration than deflection criteria alone. In addition, previous research shows no significant correlation between deflection and structural deformation of the concrete deck slab. In order to better control excess bridge vibrations and deformation‐induced structural deterioration, two new separate criteria formulations are proposed. The first formulation consists of a natural frequency criteria transformed into deflection type terms familiar to the typical bridge engineer. The second proposed formulation directly controls the acting flexural strain in the concrete deck to control deformation‐induced structural damage. The proposed serviceability criteria are applied to a database of 185 steel girder bridges. Both the as‐built behavior and the design optimized behavior are examined and compared to current AASHTO serviceability criteria. The proposed user comfort and deformation‐induced damage serviceability formulations are intended to be incorporated into ongoing Federal Highway Administration and bridge industry Long‐Term Bridge Performance research where serviceability criteria is an important component.

Select this Article		Effect of Shear Stud Connections on Dynamic Response of an FRP Deck Bridge under Moving Loads Xin Jiang, Zhongguo John Ma, F. ASCE, and Jing Song Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000401 Posted ahead of print 20 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract The main objective of this study was to evaluate the effect of shear stud connections on the dynamic response of the FRP deck system under moving loads. A FRP deck bridge in Pennsylvania was studied based on a field test and finite element (FE) analysis. In the field test, the strain of each steel girder at the mid‐span was measured at three positions: the top, the mid‐height and the bottom. In the FE analysis, the connection between the steel girders and the FRP deck was simulated as fully and partially composite, separately. Static performance under a simplified truck load was investigated based on these two FE models, and the FE analysis results were compared with the field test results to validate the FE models. The FE results of the fully composite model and the partially composite model provide a lower bound and an upper bound for the real response of the FRP deck system. Then the dynamic behavior of the FRP deck system under moving loads was studied based on the two verified FE models. The static or dynamic response in the partially composite model of the FRP deck bridge was greater than the corresponding static or dynamic response in the fully composite model. Also, it was shown that the dynamic response in the partially composite model lags behind that in the fully composite model. Additionally, the FE analysis revealed that the number of the shear stud connections affected the dynamic deflection, slip and separation. Finally, the dynamic response of the FRP deck system was compared with that of the commonly used reinforced concrete system.

Select this Article		An Experimental Analysis of a Non‐Destructive Corrosion Monitoring System for Main Cables of Suspension Bridges Matthew Jake Deeble Sloane, Raimondo Betti, Gioia Marconi, Ah Lum Hong, and Dyab Khazem Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000399 Posted ahead of print 12 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract The corrosion of the high‐strength steel wires of a suspension bridge's main cable has been attributed to the environment within the cable wrapping. A sensor network was developed to monitor and provide information to indirectly assess the environmental conditions and the deterioration of the interior of suspension bridge main cables. Both the individual sensors and the monitoring systems overall functionality was tested on a full‐scale mock‐up cable. The cable mock‐up was covered in an aluminum wrapping and an environmental chamber was built around it so as to subject the test specimen and sensor network to an aggressive corrosive environment created by cyclic temperature and humidity conditions. Temperature, relative humidity and corrosion rate levels were recorded by all sensors. The recorded data was analyzed in an attempt to determine general trends and correlations between the environmental variables themselves and their effects on corrosion rates. Recorded temperature fluctuations were highly dependent upon sensor depth within the cable; relative humidity levels, however, were not. During cyclic testing, near linear temperature increases and relative humidity decreases were recorded close to the cable's center. Baseline corrosion rate levels were affected by relative humidity levels, with significant increases in corrosion rates at relative humidity levels greater than 50%. Temperature changes proved to impact corrosion rates on a cyclic level, with high correlations between the temperature and corrosion rate readings recorded by the LPR corrosion rate sensors.

Select this Article		Evaluation of a Non‐Composite Steel Girder Bridge through Live‐Load Field Testing Sergio F. Breña, Andrew E. Jeffrey, and Scott A. Civjan Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000398 Posted ahead of print 10 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract This paper presents the field evaluation of a damaged non‐composite steel girder bridge that is part of the interstate highway system in Vermont. This bridge is typical of late 1960s construction and spans over a two‐lane state highway near the town of Weathersfield, VT. The superstructure contains three‐span continuous girders supported on abutments at the ends and on reinforced concrete multi‐column interior bents. Strains were measured during live‐load testing that was conducted to better understand the bridge behavior. The field results were compared with results from finite element models created using common engineering assumptions. In addition, the load distribution characteristics of girders that were damaged by an over height truck traveling on the state highway under the bridge were evaluated. Results indicate that alternate load paths were developed within the bridge superstructure as a result of damage from the truck impact. For the loading magnitude applied during the load tests, evidence of composite action was observed and participation of curbs on the response of the bridge was noticed. Bridge skew and partial restraint generated at supports also contributed to differences in observed and calculated responses. These nondestructive load testing results were used to provide confidence on the load carrying capacity of the bridge and to avoid costly bridge closures and detours.

Select this Article		Assessment of Cyclic Behavior of Hybrid FRP‐Concrete Columns Yilei Shi, Pedram Zohrevand, and Amir Mirmiran Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000397 Posted ahead of print 23 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract Previous experimental studies have shown superior performance of concrete‐filled fiber reinforced polymer (FRP) tubes (CFFTs) under static or pseudo‐static loading. This study has focused on the effects of fiber type and architecture and the combined shear and flexure on the cyclic behavior of CFFT columns. One control reinforced concrete (RC) and five CFFTs with different fiber type and architecture and shear span‐to‐depth ratios were tested under a constant axial load and reverse cyclic lateral loads. One of the tubes was off‐the‐shelf filament‐wound product, while the other four were made using hand lay‐up in the laboratory. The flexural strength and initial stiffness of CFFT columns were shown to be dominated by the longitudinal tensile strength and stiffness of the FRP tube, respectively. On the other hand, the modulus of elasticity of the FRP tube in both the longitudinal and hoop directions was shown to be a dominant factor in the ductility of CFFT columns. The CFFT column with the combination of carbon fibers in the longitudinal direction and glass fibers in the hoop direction showed the highest energy dissipation, and all non‐slender and slender CFFT columns showed similar mode of flexural failure. An analytical study was carried out to comprehensively investigate the effects of fiber architecture and shear span‐to‐depth ratio on the cyclic behavior of CFFT columns.

Select this Article		Partial Elastic Scheme Method in Cantilever Construction of Concrete Arch Bridges Michele Fabio Granata, Piercarlo Margiotta, Antonino Recupero, and Marcello Arici Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000396 Posted ahead of print 21 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract In this paper a study about stay stressing procedures of concrete arch bridges built by cantilevering with temporary stays is presented. Particularly the partial elastic scheme method is proposed to find the initial cable forces and a forward procedure is implemented to follow the actual sequence of construction, by extending a procedure already applied to concrete cable‐stayed bridges. The theoretical treatment is followed by a numerical application on a case‐study of a concrete arch bridge and a comparison between initial cable forces found by partial elastic scheme method and by classical backward analysis is presented here. Results show the effectiveness of the proposed procedure in order to achieve the requested design geometry of the arch and for limiting the variation of bending moments and stay forces in construction stages.

Select this Article		Experimental Study on the Dynamic Impacts of Service Train Loads on a Corrugated Steel Plate (CSP) Culvert Damian Beben Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000395 Posted ahead of print 21 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract The technical note presents the results and conclusions of the field tests under service loads that were conducted on a corrugated steel plate (CSP) railway culvert. On the basis of the measured displacements, use of the Frequency Domain Decomposition (FDD) method determined the frequencies of this culvert. Interferometric radar was used to monitor displacements of this culvert. The comparison between dynamic coefficients, received from three bridge standards and the experimental DAF, is also presented. The DAFs from tests were in the range of 1.10 to 1.375. The frequencies of CSP culvert, caused by kinematic excitations, did not exceed 5.5 Hz. In turn, the maximum displacements of the CSP railway culvert ranged from 0.08 × 10⁻³ m to 0.65 × 10⁻³ m. Conclusions drawn from the tests can be helpful in the assessment of the dynamic behavior of such CSP culverts.

Select this Article		Comparative Study on Buffeting Performance of Sutong Bridge Based on Design and Measured Spectrum Hao Wang, Ruomei Hu, Jing Xie, Teng Tong, and Aiqun Li Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000394 Posted ahead of print 16 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract The recent development in structural health monitoring (SHM) technology enables the buffeting responses of bridges to be evaluated in a more realistic manner. In this paper, the buffeting responses of cable‐stayed Sutong bridge with a main span of 1088m is analyzed with the wind spectra used in the design phase and those experimentally obtained from a long‐term SHM system to compare the actual buffeting response with design predictions. The auto‐spectra of longitudinal and vertical fluctuating wind components are derived from the in‐situ strong wind data recorded by the monitoring system. The buffeting analysis is accomplished in time domain with aeroelastic effect included. Compared with the buffeting responses obtained from measured spectrum, the girder responses from design spectrum are larger in horizontal direction and smaller in other directions, while the tower responses are lager and thus relatively conservative.

Select this Article		Effect of Train Live Load on Railway Bridge Abutments M. Esmaeili and A. Fatollahzadeh Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000393 Posted ahead of print 10 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract Assessment of lateral excess pressure due to train live load on the backfill embankment is one of the main subjects in railway bridge abutment and retaining wall design. Relevant design codes such as UIC‐776‐1R usually define a uniform infinite surcharge on the surface of embankment in order to evaluate the lateral live‐load‐induced pressure on the bridge abutments. This simplified method does not consider the actual pattern of operational live load and its induced pressure distribution on the width and height of the wall. In the current study, the operational railway live load pattern LM71, proposed by UIC‐776‐1R, was applied to accurately calculate the lateral‐induced pressure on the abutment. In this regard, the elasticity‐based equations of the lateral‐induced pressure caused by rectangular area and strip loads were utilized to evaluate the lateral pressure distribution on the abutment due to the railway live load. For evaluating the resultant lateral force and moment on the wall, a numerical integration was conducted on the lateral pressure values in the width and height of the wall. Since the lateral‐induced pressure is related to the Poisson's ratio, a sensitivity analysis was done on this parameter in order to show its effect on the resultant lateral force on the wall. As an applicable result, it was shown that, in the case of Poisson's ratio equal to 0.3, the induced resultant horizontal forces on the walls with the heights of 1.5 to 7 m, which are evaluated using the uniform surcharge of UIC, are considerably underestimated compared with the values obtained in the present study. Consequently, an analytical equation was proposed for surcharge estimation which led to a safer structural design of the railway bridge abutments.

Select this Article		Flexural Response of Continuous Concrete Beams Prestressed with External Tendons Tiejiong Lou, Sergio M. R. Lopes, and Adelino V. Lopes Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000392 Posted ahead of print 3 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract This article presents the results of a numerical investigation of the flexural behavior of continuous externally prestressed concrete beams. Aspects of behavior studied include the increase in stress in external tendons, moment redistribution in the post‐elastic range and secondary moments due to prestressing. A finite element model for the full‐range analysis of continuous externally prestressed concrete beams is introduced. The model predictions agree well with the experimental results. The analysis shows that the ultimate stress increase in external tendons of continuous beams is dependent on both the number and rotation of plastic hinges that can be developed at failure load. The degree of moment redistribution is significantly influenced by the nonprestressed tension steel and the pattern of loading. An approach based on linear transformation concept is designed to examine the secondary moments over entire loading up to the ultimate. The results indicate that the secondary moments increase linearly with the prestressing force and can be conveniently calculated by an elastic analysis.

Select this Article		Fatigue Crack Formation and Repair Strategies for Steel Cantilever Bracket Tie Plates Clay J. Naito, Xiang Li, Ian C. Hodgson, and Ben T. Yen Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000391 Posted ahead of print 3 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract A regular inspection of a bridge carrying route US422 over the Schuylkill River in Berks County Pennsylvania revealed cracks on the floor beam to cantilever bracket tie plates. Similar fatigue damage of this type has been observed over two decades ago in other bridges. During this period, much advancement has taken place in structural evaluation through finite element analysis. This paper presents a comprehensive procedure for the examination and retrofitting of tie plates using analysis and field measurement. A field and forensic investigation was conducted to examine the cause of the crack formation and the behavior of the bridge. The results of the field study and a fractographic examination confirmed that the cracks had occurred due to cyclic horizontal bending of the tie plates which was generated by secondary out‐of‐plane bending of the top of the floor beam and cantilever bracket. Field measurements and evaluation indicated that some of the as‐built tie plate details had exceeded their estimated fatigue life as computed according to specifications. An analysis by the finite element method predicted locations of likely future fatigue damage. A retrofit consisting of removal of the restraint between the tie plate and the girder by unbolting the connection, or through complete replacement of the tie plate, resulted in a significantly lower stress in the tie plate. Measurements show that the unbolted condition will allow an infinite fatigue life. The removal of the tie plate restraint, however, elevated stresses in the web region, and could produce fatigue damage in the distant future if the magnitudes of these stresses are high. This was examined through monitoring. The comprehensive procedure for investigation of tie plate cracks is recommended for handling possible future cases of similar damage.

Select this Article		Parametric Analysis of Cross‐Frame Layout on Distortion‐Induced Fatigue in Skewed Steel Bridges H. L. Hassel, C. R. Bennett, A. M. ASCE, A. B. Matamoros, A. M. ASCE, and S. T. Rolfe, Dist. M. ASCE Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000388 Posted ahead of print 21 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract The effects of skew angle, cross‐frame spacing, cross‐frame layout, cross‐frame stiffness, and load placement on the potential for distortion‐induced fatigue damage in steel bridges was investigated by performing a suite of more than 1,000 analysis jobs of high‐resolution 3D finite element models. Susceptibility to fatigue damage was quantified in terms of computed stress demand in the web gap region of the girders. Bridge configurations with three different cross‐frame layouts were evaluated, including configurations with cross‐frames placed parallel to skew angle (skewed‐parallel) and perpendicular to the girder line, both staggered (skewed‐staggered) and unstaggered (skewed‐unstaggered). Skew angles of configurations evaluated ranged between 0° and 50°, and cross‐frame spacing ranged from 2.29 to 9.14 m [7.50 to 30.0 ft]. Influence and envelope surfaces were constructed to show the relationship between load placement, location of the maximum web gap stress, and the magnitude of the maximum web gap stress. It was found that maximum web gap stress always occurred when loads were positioned directly above the intersection of a cross‐frame and girder web. The parametric study showed that cross‐frame stiffness and spacing had a significant effect on the susceptibility to distortion‐induced fatigue damage; greater cross‐frame stiffness resulted in higher web gap stresses, and increased cross‐frame spacing resulted in increased web gap stresses. It was also found that the bridge configuration was key to determining the location of the web gaps where damage is most likely to occur. In skewed‐parallel and skewed‐unstaggered layouts, maximum web gap stresses were identified in top web gaps, while in skewed‐staggered configurations maximum stresses occurred in bottom web gaps. It was found that in configurations with staggered cross‐frames, maximum web gap stresses tended to occur in regions of support, where cross‐frames are often placed back‐to‐back along the skewed alignment.

Select this Article		Reliability Based Dynamic Amplification Factor on Stress Ranges for Fatigue Design of Existing Bridges Wei Zhang, S. M. ASCE and C. S. Cai, Ph.D., P.E., F. ASCE Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000387 Posted ahead of print 11 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract A dynamic amplification factor (DAF) or dynamic load allowance (IM) is typically used in bridge design specifications to include dynamic effects from vehicles on bridges. The calculated live load stress ranges might not be correct due to varied dynamic amplification effects in different regions along the bridge, different road roughness conditions, and multiple stress range cycles generated for one vehicle passage on the bridge. In the present study, a reliability based dynamic amplification factor on stress ranges (DAFS) for fatigue design is proposed to include the fatigue damages from multiple stress range cycles due to each vehicle passage at varied vehicle speeds under various road conditions in the bridge's life cycle. A numerical simulation toward solving a coupled vehicle‐bridge system, including a 3‐D suspension vehicle model and a 3‐D dynamic bridge model, is used to obtain the revised equivalent stress range. The revised equivalent stress range is defined on an equivalent fatigue damage basis, namely, the fatigue damages from multiple stress ranges with varied amplitudes are equivalent with the fatigue damage from one stress cycle of the revised equivalent stress range. DAFS is then defined as the ratio of the nominal live load stress range and the maximum static stress range. A parametric study on DAFS is carried out to analyze the effect from multiple variables in the bridge's life cycle, for instance, faulting days in each year, vehicle speed limit and its coefficient of variance, vehicle type distribution, and annual traffic increase. In order to appreciate the difference of the proposed DAFS and traditional DAF, the calculated fatigue lives from the six approaches related to DAFS or DAF are compared with each other. Similar to DAF for dynamic response on displacements, DAFS is proposed to obtain dynamic stress ranges for fatigue design. As a result, once the DAFS is available, the dynamic stress ranges for fatigue design can be easily obtained by multiplying the maximum static stress range and the DAFS, which helps preserve both the accuracy and simplicity for bridge fatigue design.

Select this Article		Measurement System Configuration for Damage Identification of Continuously Monitored Structures Irwanda Laory, Nizar Bel Hadj Ali, Thanh N. Trinh, and Ian F. C. Smith Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000386 Posted ahead of print 11 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract Measurement system configuration is an important task in structural health monitoring in that decisions influence the performance of monitoring systems. This task is generally performed using only engineering judgment and experience. Such approach may result in either a large amount of redundant data and high data‐interpretation costs, or insufficient data leading to ambiguous interpretations. This paper presents a systematic approach to configure measurement systems where static measurement data are interpreted for damage detection using model‐free (non‐physics‐based) methods. The proposed approach provides decision support for two tasks: (1) determining the appropriate number of sensors to be employed and (2) placing the sensors at the most informative locations. The first task involves evaluating the performance of measurement systems in terms of the number of sensors. Using a given number of sensors, the second task involves configuring a measurement system by identifying the most informative sensor locations. The locations are identified based on three criteria: the number of non‐detectable damage scenarios, the average time to detection and the damage detectability. A multi‐objective optimization is thus carried out leading to a set of non‐dominated solutions. To select the best compromise solution in this set, two multi criteria decision making methods, Pareto‐Edgeworth‐Grierson multi‐criteria decision making (PEG‐MCDM) and Preference Ranking Organization METhod for Enrichment Evaluation (PROMETHEE), are employed. A railway truss bridge in Zangenberg (Germany) is used as a case study to illustrate the applicability of the proposed approach. Measurement systems are configured for situations where measurement data are interpreted using two model‐free methods: Moving Principal Component Analysis (MPCA) and Robust Regression Analysis (RRA). Results demonstrate that the proposed approach is able to provide engineers with decision support for configuring measurement systems based on the data‐interpretation methods used for damage detection. The approach is also able to accommodate the simultaneous use of several model‐free data‐interpretation methods. It is also concluded that the number of non‐detectable scenarios, the average time to detection and the damage detectability are useful metrics for evaluating the performance of measurement systems when data are interpreted using model‐free methods.

Select this Article		Instrumentation and Modeling of I35W St. Anthony Falls Bridge Brock D. Hedegaard, Catherine E. W. French, Carol K. Shield, Henryk K. Stolarski, and Ben J. Jilk Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000384 Posted ahead of print 9 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract The I‐35W St. Anthony Falls Bridge was constructed to replace the steel truss bridge that collapsed on August 1, 2007. The design of the replacement bridge featured a “smart bridge” system. The smart bridge concept included instrumentation for long‐term monitoring of the structural behavior of the bridge. Truck load tests were conducted prior to opening the bridge and 26 months later to measure the response of the structure under controlled loading. The measurements were used to validate a finite element model of the bridge constructed to further investigate the behavior of the structure. The correlation between computed and measured results was found to be good. This paper describes the bridge, the instrumentation installed within the bridge, the finite element model, and validation of the model with respect to the truck load tests. Recommendations are provided for static instrumentation plans of concrete box girder structures.

Select this Article		Evaluating Codes Criteria for Regular Seismic Behavior of Continuous Concrete Box Girder Bridges with Unequal Height Piers J. E. B. Guirguis and S. S. F. Mehanny, M. ASCE Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000383 Posted ahead of print 3 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract The seismic design and response prediction of irregular bridges supported on piers of unequal heights ‐ a commonly adopted solution when crossing steep‐sided valleys ‐ represent a particularly challenging problem that is yet not effectively addressed by seismic design code provisions worldwide. From a force‐based design perspective, shorter piers are subjected to increased ductility demand and consequently damage tends to localize in these relatively stiff piers at increasing seismic hazard levels. This paper presents an investigation of the seismic response of a few schemes of a three‐span case‐study continuous bridge, commonly encountered in practice, featuring two unequal piers with relative heights of 0.5, 0.64, 0.75 and 0.86, respectively. Static pushover and time history (under incrementally scaled‐up actual records) nonlinear inelastic analyses are performed using OpenSees to check the validity of Eurocode 8 (EC8) and newly proposed American Association of State Highway and Transportation Officials (AASHTO‐LRFD) provisions for regular seismic behavior of ductile bridges dimensioned per a force‐based design procedure. It has been demonstrated that satisfying EC8 regularity condition does not necessarily result in a near‐simultaneous failure of unequal piers at the extreme hazard level, especially for a low ratio between piers heights (≤0.5). It has been further concluded that regularity criteria in both provisions fall short of providing absolute regular seismic behavior of the bridge under investigation. Finally, a new design criterion is introduced (and verified) herein and is promoted for bridges with unequal height piers but with same cross‐section dimensions as may be typically dictated by some compelling aesthetical and practical considerations. It is however worth pointing that piers’ behavior (and hence failure) is assumed to be governed by flexure, and no shear failure or buckling are considered.

Select this Article		Development of State‐Specific Load and Resistance Factor Rating Method Michel Ghosn, Bala Sivakumar, and Feng Miao Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000382 Posted ahead of print 1 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract Recognizing the limitations of the generic truck weight data and conservative assumptions made during the calibration of live load factors for bridge rating, the AASHTO Load and Resistance Factor Rating (LRFR) Manual for Bridge Evaluation (MBE) provides sufficient flexibility and allows state agencies to adjust the live load factors based on their individual conditions and site‐specific or state‐specific information. This paper describes the reliability‐based process that can be followed to perform such adjustments and illustrates its application using as an example the procedure followed during the calibration of an LRFR methodology for New York State Bridges. This methodology is applied to the rating of existing bridges, the posting of under‐strength bridges, and the checking of permit trucks. The live load models used during the calibration are based on Weigh‐In‐Motion (WIM) data collected from several representative sites. The LRFR live load factors developed using the proposed calibration process would provide uniform and consistent levels of bridge safety and reliability for the bridge classes and configurations targeted. The target reliability levels used during the calibration should reflect the experience gained by state bridge engineers from the evaluation of existing bridges under current loading conditions.

Select this Article		Development of an Efficient Maintenance Strategy for Corroded Steel Bridge Infrastructures J. M. R. S. Appuhamy, M. Ohga, T. Kaita, P. Chun, and P. B. R. Dissanayake Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000381 Posted ahead of print 1 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract The potential for the structural capability degrading effects due to corrosion is of profound importance and must be both fully understood and reflected in bridge inspection and maintenance programmes. As the number of steel bridge infrastructures increase throughout the world, it is an exigent task to conduct regular and detailed corrosion surface investigations in order to evaluate their residual strength capacities and develop analytical models to understand their present conditions, critical locations as well as yield and ultimate behaviors. This paper presents a simple, accurate and rapid assessment method and an effective maintenance management strategy developed by using the results of tensile coupon tests conducted on many corroded plates obtained from a steel plate girder used for about 100 years with severe corrosion condition and FEM analytical approach proposed by measuring only the maximum corroded depth (t_c,max), which can be used to make reliable decisions affecting the cost and safety.

Select this Article		Cyclic Behavior of FRP‐Concrete Bridge Pier Frames Bin Li, Pedram Zohrevand, and Amir Mirmiran Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000380 Posted ahead of print 31 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract Concrete‐filled fiber reinforced polymer (FRP) tubes (CFFT) were initially developed without any internal steel reinforcement as viable alternatives to conventional reinforced concrete (RC) columns in non‐seismic regions. Studies have since shown that extending CFFT application to seismic regions requires a moderate amount of internal steel reinforcement. To date, cyclic performance of CFFTs as part of a structural frame has not been assessed. This paper describes testing of four 1/6‐scale two‐column bents; a control RC, a glass FRP‐concrete (GFF), a carbon FRP‐concrete (CFF), and a hybrid glass/carbon FRP‐concrete frame (HFF). Each frame was tested under reverse cyclic lateral loading with a constant axial load. Specimen HFF with hybrid FRP tubes demonstrated the highest moment capacity and initial stiffness, with an increase of 200% and 70%, respectively, over the control specimen. Specimen GFF showed no sign of cracking up to a drift ratio of 15% with considerable residual strength, while Specimen CFF had the least ductility. Glass FRP tubes extended the plastic hinge length of the pier columns to twice that of the control RC frame.

Select this Article		A Field Test of Magnetic Methods for Corrosion Detection in Prestressing Strands in Adjacent Box‐Beam Bridges Bertrand Fernandes, Michael Titus, Douglas Karl Nims, M. ASCE, P.E., Al Ghorbanpoor, F. ASCE, P.E., and Vijay Devabhaktuni Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000379 Posted ahead of print 31 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract Magnetic methods are progressing in the detection of corrosion in prestressing strands in adjacent precast, prestressed concrete box‐beam bridges. This study is the first field trial of magnetic strand defect detection systems on an adjacent box‐beam bridge. A bridge in Fayette County, Ohio, which was scheduled for demolition, was inspected. The prestressed box‐beams had significant strand corrosion. The corroded strands show discontinuities and a reduced cross‐sectional area. These changes are reflected in the magnetic signatures of the prestressing steel. Corrosion in the prestressing steel was detected using two magnetic methods, namely the “magnetic flux leakage” and the “induced magnetic field” methods. The purpose of these tests was to demonstrate the ability of the magnetic methods to detect hidden corrosion in box‐beams in the field and tackle the logistic problem of inspecting box‐beams from the bottom. The inspections were validated by dissecting the bottom of the box‐beams after the inspections. The results showed that the magnetic flux leakage method detects hidden corrosion and strand breaks with a sufficient amount of accuracy. Both magnetic field methods were also able to estimate corrosion by detecting the effective cross‐sectional area of strand. Thus, it was shown that the magnetic methods can be used with sufficient reliability to predict hidden corrosion in prestressing strands of box‐beams. Recommended actions to make magnetic inspection practical are discussed.

Select this Article		Longitudinal Joints with Accelerated Construction Features in Decked Bulb‐Tee Girder Bridges: Strut‐and‐Tie Model and Design Guidelines Zhi‐Qi He, Zhongguo John Ma, F. ASCE, Cheryl E. Chapman, and Zhao Liu Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000378 Posted ahead of print 31 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract This paper focuses on the development of a strut‐and‐tie model that can be used in the design of previously developed longitudinal joints with accelerated construction features. Four joint specimens reinforced with tight bend diameter U‐bars and previously tested under bending are summarized here to validate the strut‐and‐tie model (STM). The validated STM is proposed to calculate the ultimate moments of the joints, which is capable of identifying the most critical parameters and yields safe and consistent predictions. It shows that the joint capacity increases with the increasing of concrete strength and overlap length, and the capacity reaches the maximum value when the U‐bar spacing is twice the overlap length. Design recommendations to U‐bar spacing, overlap length, diameter of lacer bars, as well as concrete strength of the closure pour material are developed for full‐strength joints.

Select this Article		Bending Strength of Horizontally Curved Composite I‐Girder Bridge Chai H. Yoo, F. ASCE, Kyungsik Kim, Kyoung C. Lee, A. M. ASCE, and Junsuk Kang Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000377 Posted ahead of print 26 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract Horizontally curved I‐girders are subjected to combined vertical bending and torsion under gravity loads alone. The torsional behavior of open I‐shaped girders is commonly and conveniently transformed to self‐equilibrating lateral bending of flanges. The interaction of vertical bending and lateral flange bending reduces the vertical moment carrying capacity of the section. The interaction equations for predicting the nominal bending strength of horizontally curved I‐girders of compact‐flange sections subjected to vertical moment and torsion have been derived. Singly symmetric composite and noncomposite I‐shaped cross sections in the positive and negative moment zones, respectively, are considered. These strength criteria are based purely on the static equilibrium of the cross section with no secondary amplification considered. The limitations and applicability of the derived equations toward the design use are demonstrated and analyzed.

Select this Article		A Probability of Collapse Expression for Bridges Subject to Barge Collision Michael T. Davidson, A. M. ASCE, Gary R. Consolazio, M. ASCE, Daniel J. Getter, S. M. ASCE, and Falak D. Shah, S. M. ASCE Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000376 Posted ahead of print 20 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract Accounting for waterway vessel collision is required in the structural design of bridges spanning navigable waterways. During collision events, massive waterway vessel groups such as barge flotillas are capable of dynamically transmitting horizontal forces to impacted bridge components. Furthermore, collision‐induced forces can be sufficient to collapse piers or roadway spans in the vicinity of the impact location. If collapse takes place, economic loss is suffered due to subsequent traffic rerouting and bridge replacement costs. Additionally, fatalities may occur if the roadway is occupied during or shortly after collapse. This paper focuses on the development of a probability of collapse expression for bridge piers subject to barge impact loading, where the relationship can be readily integrated into existing bridge design methodologies. The expression is developed by employing probabilistic descriptions for a multitude of random variables related to barge traffic characteristics and bridge structures in conjunction with nonlinear dynamic finite element analyses of barge‐bridge collisions. Highly efficient, advanced probabilistic simulation techniques are necessarily incorporated into the barge‐bridge collision analysis framework to allow feasible estimation of structural reliability parameters. These parameters facilitate the formation of an expression that, in turn, bridge designers can use to estimate probabilities of structural collapse due to barge collision, without performing probabilistic analyses.

Select this Article		Stress‐Laminated‐Timber Decks Subjected to Eccentric Loads in the Ultimate‐Limit State K. Ekholm, R. Crocetti, and R. Kliger Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000375 Posted ahead of print 20 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract Stress‐laminated‐timber (SLT) bridge decks are generally designed using either linear hand calculation methods or linear finite element models. Several studies have shown, however, that the behaviour of SLT decks is non‐linear when loaded until failure. In this paper, several linear design methods are compared with one another and with an ultimate‐load test of a full‐scale SLT deck subjected to an eccentric load. Some of the linear hand calculation methods show significant discrepancies in results, depending on the load position. There are also variations in the results from finite element models, depending on the material properties assigned to the deck. All the design methods failed to predict the deflection of the tested deck when loaded to failure. A larger deflection was observed in the full‐scale test than that predicted by the design methods. As a result, the linear design method could underestimate the bending stresses in the deck. Several hand calculation methods are also unable to calculate the transverse forces and moments necessary for design according to Eurocode 5.

Select this Article		Total Cost‐Benefit Analysis of Alternative Corrosion Management Strategies for a Steel Roadway Bridge Scott Walbridge, M. ASCE, Dilum Fernando, and Bryan T. Adey Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000374 Posted ahead of print 20 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract This paper describes a methodology for evaluating alternative corrosion management strategies for a steel roadway bridge based on a total cost‐benefit analysis. In this analysis, the impacts of girder type and preservation intervention selection on the bridge owner, users, and public are considered. The methodology is demonstrated for a steel girder bridge in Wallis, Switzerland. In this demonstration, painted carbon steel and unpainted weathering steel girders are investigated. The investigated preservation interventions are: protection by painting, protection by metalizing, and replacement. Deterioration of the girders by corrosion is modeled probabilistically. Following the methodology demonstration, sensitivity studies are performed, wherein the corrosion environment, traffic volume, and detour length during interventions are varied. The effects of these variations on the different benefit types are then discussed and the conditions under which the different corrosion management strategies may be optimal are identified.

Select this Article		Damage Evaluation for Concrete Bridge Deck by Means of Stress Wave Techniques Tomoki Shiotani, Hiroyasu Ohtsu, Shohei Momoki, Hwa Kian Chai, Hiroshi Onishi, and Toshiro Kamada Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000373 Posted ahead of print 20 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract Different from post failure maintenance in many perspectives, preventive maintenance of civil engineering structures is another highly crucial measure not only for achieving efficient distribution of limited budget over existent ageing infra‐structures, but also for maximizing their service life spans. In the context of road bridges, their functional failure often causes serious impact on safety and logistics, which could turn out to be detrimental to the social economy. To appropriately maintain a huge number of ageing infrastructures, a strategic maintenance program facilitating both the global and local‐diagnosis approaches, which in addition is effective in assessing early damage, is of high demand. In this study, fatigue damage of concrete bridge decks, which is a common form of deterioration among bridges, was examined by sensitive non‐destructive testing methods utilizing propagation of stress waves. Specifically, the fatigue damage process of concrete decks due to repeated traffic loads is visualized by means of active and passive elastic wave techniques, namely the elastic wave tomography and acoustic emission techniques. In the experiment, a full‐scale concrete deck was subject to repeatedly moving wheel load to induce fatigue damage to the concrete. At three stages of intact (promptly after initial loading), 10,000 passages and 20,000 passages of 150 kN‐wheel loading, the fatigue test would be suspended temporarily to make way for inspections of the structure interior by transmitting elastic waves in concrete for measuring the change in velocity. Applying static load with gradual increment in magnitude, acoustic emission testing was then conducted to extract characteristic AE parameters with regard to the intrinsic damage. Promising elastic wave parameters for quantifying the damage, which have been identified through experimental studies, were later verified using in‐situ deck specimens hewed out from an actual bridge. Through the experiments, it was obvious that by using sparsely arrayed AE sensors for measurement, followed by extracting AE frequency features, global investigation of bridge decks’ integrity could be carried out. And once the area of interest was identified through analysis of AE data, detailed information such as cross‐sectional damage could be visualized by employing ultrasonic testing and tomographic reconstruction procedure.

Select this Article		Effect of Temperature on Daily Modal Variability of a Steel‐Concrete Composite Bridge Amir A. Mosavi, Rudolf Seracino, and Sami Rizkalla Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000372 Posted ahead of print 20 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract Vibration‐based damage detection techniques typically use changes of modal characteristics of bridges as a possible indication of damage. However, structural damages are not the only cause of these changes. This study investigates the effect of temperature variations on modal characteristics of a two span steel‐concrete composite bridge in North Carolina, USA, and addresses the extent and reason of the daily changes observed in its dynamic properties. The field testing in this study included measuring the vibration responses, deflections and temperatures of the bridge throughout a summer day. The dynamic characteristics of the bridge, derived from measurements at different times of the day, were compared to each other. Recorded temperatures and deflections of the bridge deck were used to address the observed changes in the natural frequencies of the bridge. Results of the field testing show that temperature variations can induce modal variability on a daily cycle. A primary reason for this observation can be attributed to the temperature gradients measured on the bridge deck from night to noon.

Select this Article		Probabilistic Modeling of Bridge Deck Unseating during Hurricane Events Navid Ataei, S. M. ASCE and Jamie E. Padgett, A. M. ASCE Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000371 Posted ahead of print 12 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract Although coastal bridges have exhibited significant susceptibility to damage during hurricane induced wave and surge events, probabilistic models are lacking to quantify the vulnerability of bridges under a range of structural or hazard parameters and support hurricane risk assessment and mitigation activities. This paper introduces a computationally efficient methodology to assess the fragility, or conditional failure probability, of bridges targeting the deck shifting or unseating failure mode, which is a predominant severe mode of failure for vast inventories of simply supported span bridges. The method propagates uncertainties in parameters affecting the structural capacity and demand, such as mass density, connection strength, material properties, workmanship, and wave parameters. Fragility surfaces are derived in which failure probability is presented over a range of relative surge elevation and wave heights. The application of this technique is shown through a regional fragility assessment of 136 bridges in the greater Houston area. The results reveal that a failure zone emerges in the fragility surfaces of the bridges studied, with a dramatic transition in probability of failure. Additionally, bridges with similar trends in fragility surfaces can be readily classified based on estimates of their mean mass per span length. Finally, the application of the new vulnerability models in a case study regional risk assessment for Hurricane Ike reveal consistency with observed damage, and also offers an opportunity for future studies to investigate alternative scenarios for risk mitigation planning or extensions of the methodology to consider other regions or failure modes.

Select this Article		Reliability‐Based Calibration of Load Factors for LRF Design of Reinforced Concrete Bridges under Multiple Extreme Events: Scour and Earthquake Azadeh Alipour, A. M. ASCE, Behrouz Shafei, A. M. ASCE, and Masanobu Shinozuka, Dist. M. ASCE Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000369 Posted ahead of print 6 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract A multi‐hazard reliability‐based framework is developed through this study to evaluate the structural response of reinforced concrete bridges under the combined effects of pier scour and earthquake events. This framework is utilized to calibrate the scour load modification factors for design of bridges located in high seismic areas. Towards this goal, a series of case‐study bridges are investigated. For each bridge case, the joint probability of failure due to scour and earthquake hazards is determined for a range of expected combinations of these two extreme events. The occurrence probability of each scour‐earthquake scenario is probabilistically identified by taking into account all the major sources of load uncertainty through scour risk and seismic hazard curves. Furthermore, the uncertainties inherent in the structural response of bridges are included in the framework to improve the accuracy of estimated failure probabilities. The calculated probabilities are then compared with the maximum acceptable probability of failure (or its equivalent target reliability index) given by current design codes to obtain scour load modification factors. The developed framework provides a reliable approach for calibration of the code specifications in the extreme event situations and can be extended to other combinations of natural hazards.

Select this Article		Using Weigh‐In‐Motion Data to Determine Aggressiveness of Traffic for Bridge Loading Eugene J. OBrien and Bernard Enright Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000368 Posted ahead of print 6 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract This paper presents results based on the analysis of an extensive database of weigh‐in‐motion (WIM) data collected at five European highway sites in recent years. The data are used as the basis for a Monte Carlo simulation of bridge loading by two lane traffic, both bidirectional and same‐direction. Long runs of the simulation model are used to calculate characteristic bridge load effects (bending moments and shear forces), and these characteristic values are compared with design values for bridges of different length as specified by the Eurocode for bridge traffic loading. Various indicators are tested as possible bases for a “Bridge Aggressiveness Index” to characterize the traffic measured by the WIM data in terms of its influence on characteristic bridge load effects. WIM measurements can thus be used to determine the “aggressiveness” of traffic for bridges. The mean maximum weekly gross vehicle weight is proposed as the most effective of the indicators considered and is shown to be well correlated with a wide range of calculated characteristic load effects at each site.

Select this Article		Experimental Study on Fatigue Strength of Corroded Bridge Wires Shunichi Nakamura and Keita Suzumura Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000366 Posted ahead of print 5 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract Fatigue tests were conducted for corroded galvanized steel wires on three corrosion levels, showing that fatigue strength of corroded wires lowers as corrosion progresses. Corrosion pits were measured on the corroded specimens, showing severer corrosion produced deeper pits in more condensed areas. Fatigue tests were then conducted for wire specimens with artificial pits whose sizes were decided by the measured corrosion pit data. Three different pit shapes were assumed: round, triangle and triangle with a notch. The wire specimens with round pits did not break until one million cycles in the stress range of 400 MPa. Fatigue strength of wires with triangle pit was lower than that with a round shape. Triangle pit specimens broke at fewer cycles for shorter pit length. Fatigue strength of wires with notched triangle further decreased and critical cycles did not depend on pit length. As the S‐N relation of the wire specimens with triangle pits and notched triangle pits has a similar tendency as those of the actually corroded wires, the pit shape seems to be a dominant factor to lower fatigue strength. Stress concentration factor at the sharp edge of pits were obtained by strain gauge measurement and FEM analysis. Both methods showed that stress concentration is larger for sharper pit shapes, indicating that this is the major cause for decrease of fatigue strength.

Select this Article		Automated Ice Inference and Monitoring on the Veterans' Glass City Skyway Bridge J. Kumpf, A. Helmicki, D. K. Nims, V. Hunt, and S. Agrawal Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000365 Posted ahead of print 5 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract Under certain weather conditions, the Veterans' Glass City Skyway (VGCS) Bridge in Toledo, OH accumulates ice on the stay sheaths in such a way that has led to large fragments falling into traffic lanes. In order to aid the Ohio Department of Transportation (ODOT) in their response to this, an automatic inference and monitoring system was implemented. This system utilizes existing weather station measurement data to infer possible events, alerting officials and providing tools to further assess the situation. The development of the decision, the algorithm and implementation process are presented. The system was implemented in January of 2011, and it warned of and monitored an icing event that occurred February 20^th to 24^th, 2011. Ice fell shortly after the system indicated conditions were met for ice fall. ODOT personnel used the ice inference system to assist them in managing the response to the icing event.

Select this Article		Cable‐Stayed Bridges: A Case Study for Ambient Vibration‐Based Cable Tension Estimation S. Kangas, A. Helmicki, V. Hunt, R. Sexton, and J. Swanson Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000364 Posted ahead of print 5 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract A cable‐stayed bridge recently constructed by the Ohio Department of Transportation incorporates measures put forth by a Federal Highway Administration study to mitigate stay motion. In following recent trends, the stays at this bridge are built without the use of grout for the purposes of inspection and, if necessary, replacement. Several experiments were performed to determine the viability of using traditional vibration techniques, which assume an integral sheath, to estimate cable tension with this new configuration.

Select this Article		Development Length Tests of Full‐Scale Prestressed Self‐Consolidating Concrete Box and I‐Girders Bassem Andrawes, A.M.ASCE, Andrew Pozolo, and Zhe Chen Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000363 Posted ahead of print 23 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract Self‐Consolidating Concrete (SCC) is a highly workable concrete with tremendous potential to reduce the production time and cost of precast members. Institutions in Japan, Europe, and the United States have successfully utilized SCC in large‐scale applications, particularly in bridges. However, lack of experimental data has hindered SCC's implementation in prestressed design. This paper reports the findings of a study investigating the development length of steel strands in SCC full‐scale prestressed bridge girders. Flexural tests are conducted on two 8.5‐m long box girders and two 14.6‐m long I‐girders cast with SCC to determine the development length of their 12.7‐mm diameter prestressing steel strands. Experimental results are compared to requirements of the American Concrete Institute and the American Association of State Highway and Transportation Officials. Results are also compared to analytical expressions for development length proposed in literature.

Select this Article		A Vibration Based Method and Sensor for Monitoring of Bridge Scour Ali Zarafshan, Amirhossein Iranmanesh, and Farhad Ansari Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000362 Posted ahead of print 23 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract Scour is the major cause for many bridge failures and damage to piers and abutments. Scour is not easily discernible since it is hidden under the channel flow. Over the years, a number of sensors have been developed for detection of scour depth. Development, testing and field implementation of a new and simple type of scour sensor is described in this article. The scour depth detection concept is based on measuring the fundamental frequency of vibration for a rod embedded in the riverbed. The sensor uses a single Fiber Optic Bragg Grating (FBG) sensor for transduction of the vibration frequency. The inverse relationship between the fundamental frequency and the length of the sensor rod is used for detection of the scour depth. A computational approach is developed based on the Winkler spring reaction soil model for automated calibration of the scour sensor during installation in the riverbed. The scope of the research included development of the theoretical basis for the sensor, establishment of the computational methodology for detection of the riverbed foundation properties, proof of concept laboratory tests, small scale field verification tests, and installation and remote monitoring of scour in a multi‐span scour critical bridge in Illinois. Results include laboratory test data from measurements in soil, simulated scour tests in a hydraulic flume, and real time data from remote monitoring of scour at the bridge site.

Select this Article		Design and Development of In‐Situ Fatigue Sensors for SHM of Highway Bridges B. H. M. Priyantha Wijesinghe, Scott A. Zacharie, Kyran D. Mish, and J. David Baldwin Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000361 Posted ahead of print 14 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract Initial development work for an in‐situ fatigue sensor for the detection of fatigue damage in steel bridge structures is presented. The in‐situ fatigue sensor is designed to be bonded to the base structure and is based on the strain‐life fatigue analysis method. Sensors are constructed of electrically conductive material with notched sensor arms producing varying stress concentration factors (SCF). The sensor operates on the principle of predictable progressive failure of the parallel arms as fatigue damage is accumulated in the base structure. Experimental results of the behavior of the fatigue sensor under constant amplitude loading of a base structure‐mimicking carrier specimen are compared with the simulation results obtained by the finite element analysis method and show reasonable agreement.

Select this Article		A Hybrid Simulation Testbed for Experimental Validation and Characterization of NDE and Sensor Technology Michael W. Mercado and Yunfeng Zhang Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000360 Posted ahead of print 14 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract An increasing number of online structural health monitoring systems have begun to be implemented on bridges, which are often comprised of a variety of local sensing and non‐destructive evaluation (NDE) devices. However, before any new type of sensor and NDE technology such as ultrasonic surface wave sensors can be deployed for field implementation, they need first to be validated and characterized under realistic loads and environmental conditions in a controlled lab setting. This paper demonstrates the use of a hybrid testing setup to create a characterization testbed for more realistic evaluation of NDE and sensor technologies. In this study, a prototype bridge structure based on the Yellow Mill Pond Bridge in Connecticut was selected to demonstrate the features and issues of a hybrid simulation testbed for sensor characterization such as flexibility in traffic load representation and large scale specimen even with small testing equipment. Using this prototype bridge structure, a series of hybrid simulation tests using real variable‐amplitude traffic loading were performed on a 0.6‐scale steel flange plate specimen with a welded cover plate. Features of this hybrid simulation testbed are discussed here including the complexity of the virtual model (e.g., the dynamic mass effects and damping of the structure) and stability issues that can develop in the test. Finally, the ability of the hybrid testing platform to evaluate sensor performance under varying environmental conditions was demonstrated for elevated temperatures. Although strain gage was used to demonstrate the technology here, the sensor testbed can be used for general characterization of other types of NDE devices and sensors.

Select this Article		Imaging Tools for Evaluation of Gusset Plate Connections in Steel Truss Bridges Christopher Higgins and O. Tugrul Turan Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000358 Posted ahead of print 8 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract After the collapse of the I35W Bridge in Minneapolis, MN in 2007, transportation agencies began evaluating and rating their inventories of gusset plate connections. Connection evaluations require accurate drawings that detail the plate, member, and fastener geometries. These structural details should also accurately reflect the as‐built conditions. For some connections, as‐built information may not be available or the available drawings may not represent the actual field conditions. To fill this gap, a new methodology was developed that enables rapid and accurate collection of field measurements for connection plate geometry. The method uses close‐range photogrammetry techniques to rectify images taken with consumer grade cameras using flat‐field and fisheye lenses. The technique has been demonstrated on full‐scale gusset plates in the laboratory and in the field. Dimensional measurements from the processed images provided results that are as good as or better than conventional field measurements and with tolerances below what most engineers require for calculation of gusset plate connection capacity. This technique provides a new tool for bridge engineers to quickly collect gusset plate geometry that can be used in connection evaluations and rating, and can further enhance bridge management tasks.

Select this Article		Performance Testing of a Road Bridge Deck Containing Flat Rail Wagons Lungten Jamtsho and Manicka Dhanasekar Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000357 Posted ahead of print 8 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract A road bridge containing disused flatbed rail wagons as the primary deck superstructure was performance tested in a low volume, high axle load traffic road in Queensland, Australia; some key results are presented in this paper. A fully laden truck of total weight 28.88 % of the serviceability design load prescribed in the Australian bridge code was used; its wheel positions were accurately captured using a high speed camera and synchronised with the real‐time deflections and strains measured at the critical members of the flat rail wagons. The strains remained well below the yield and narrated the existence of composite action between the reinforced concrete slab pavement and the wagon deck. A three dimensional grillage model was developed and calibrated using the test data, which established the structural adequacy of the rail wagons and the positive contribution of the reinforced concrete slab pavement to resist high axle traffic loads on a single lane bridge in the low volume roads network.

Select this Article		Sensor Networks, Computer Imaging and Unit Influence Lines for Structural Health Monitoring: A Case Study for Bridge Load Rating F. Necati Catbas, Ricardo Zaurin, Mustafa Gul, and H. Burak Gokce Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000288 Posted ahead of print 7 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract In this paper, a novel methodology for Structural Health Monitoring (SHM) of a bridge is presented with implementations for bridge load rating using sensor and video image data from operating traffic. With the methodology demonstrated in this paper, video images are analyzed by means of computer vision techniques to detect and track vehicles crossing the bridge. Traditional sensor data is correlated with computer images to extract Unit Influence Lines (UIL). Based on laboratory studies, it is shown that UIL can be extracted for a critical section with different vehicles by means of synchronized video and sensor data. In this paper, it is presented that the synchronized computer vision and strain measurements can be obtained for bridge load rating under operational traffic. For this, the following are presented: a real life bridge is instrumented, monitored and the real life data is processed under moving load. A detailed Finite Element Model (FEM) of the bridge is also developed and presented along with the experimental measurements to support the applicability of approach for load rating using unit influence lines extracted from operating traffic. The load rating of bridges using operational traffic in real life was validated with the FEM results of the bridge and the simulation of the operational traffic on the bridge. This approach is further proven with different vehicles captured with video and measurements. The UILs are used for load rating by multiplying the UIL vector of the critical section with the load vector from the HL‐93 design truck. The load rating based on the UIL is compared with the FEM results, indicating good agreement. With this method, it is possible to extract UIL of bridges under regular traffic and obtain load rating efficiently.

Select this Article		On the Use of Ultrasound Excited Thermography Applied to Massive Steel Components ‐ An Emerging Crack Detection Methodology Robin Plum and Thomas Ummenhofer Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000355 Posted ahead of print 7 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract In the field of non‐destructive testing of structural components, active thermography methods are increasingly in demand. The most experience is available in testing of CFRP or similar types of composite material. One of the emerging techniques is ultrasound excited thermography, which has not been fully transferred to massive steel members used in constructional steelwork so far. The idea of ultrasound excitation is to generate elastic waves that propagate inside the investigated structure. In case of internal flaws, such as cracks, the boundary faces move relatively to each other. The resulting rubbing and clapping of crack faces generates frictional heat, which is detected by means of an infrared camera. This paper demonstrates the usage of high‐frequency mechanical excitation to detect cracks in hot‐rolled girders and reduced plate specimens. The ultrasonic lock‐in and the ultrasonic sweep thermography approaches are presented. Localized heating of the crack regions and distributed heating patterns due to material damping can be observed. The influences of the tuned frequency and the crack depth as well as effects of pre‐stressing and repeated excitation are discussed. Besides experimental results, a finite element simulation of the thermo‐structural problem is conducted. The model can be easily adjusted to match experimental results of a performed ultrasonic sweep thermography.

Select this Article		Fatigue Reliability Updating Evaluation of Existing Steel Bridges Chunsheng Wang, Long Hao, and Bingning Fu Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000354 Posted ahead of print 7 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract Through modern nondestructive inspection (NDI) techniques, fatigue cracks can be detected with varying accuracies in steel bridge structures, and consequently assessment and updating of fatigue reliability can be performed. A probabilistic fracture mechanics method based on the Bayes theorem using information from NDI has been demonstrated to update the relevant parameters of crack growth models effectively. Using the probabilistic characteristics of the NDI techniques, the probabilistic fatigue failure method and the Bayes theorem, a procedure for assessing and updating the fatigue reliability of existing steel bridge components is presented. Data collected from two steel bridges — Zhejiang Street Bridge and Ganjiang River Bridge are used to illustrate the fatigue reliability assessment and updating method. In the case study, the suspender β ‐ T curves of the Zhejiang Street Bridge and the Ganjiang River Bridge are determined after inspection and updating. It is found in this research that fatigue reliability of the selected members in the existing steel bridges increases with no cracks detected, and decreases with no size cracks detected, and changes remarkably with cracks detected.

Select this Article		An Approach to Reduce the Limitations of Modal Identification in Damage Detection Using Limited Field Data for Non‐Destructive SHM of a Cable‐Stayed Concrete Bridge Z. Ismail, Z. Ibrahim, A. Z. C. Ong, and A. G. A. Rahman Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000353 Posted ahead of print 7 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract The objective of the study was to propose a technique to reduce the limitations of modal identification in damage detection using reduced field data for non‐destructive SHM of a cable‐stayed concrete bridge. Simply supported bridge models were constructed with predetermined damage at mid‐span of the bridge. The technique necessitated the performance of linear and eigen analyses on the control beam, and nonlinear analysis on the bridge with damage. Residuals from regression of the mode shape using the Chebyshev series rational on the modal frequencies and transformation and application into the fourth order centered finite divided difference formula were shown. The use of the regressed mode shapes for the reinforced concrete bridge model showed very large residuals around the areas of the damage. The results showed that the method was successful in assisting to reduce the limitations of modal identification in locating damage on a bridge model with limited field data and was comparable with other techniques proposed by other researchers in terms of its simplicity.

Select this Article		Experimental Study on Shear Behavior in Negative Moment Regions of Segmental Externally Prestressed Concrete Continuous Beams Guoping Li, Chunlei Zhang, and Changyan Niu Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000351 Posted ahead of print 2 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract External prestressing technology has achieved wide application in bridges. Though previous tests have made great progress in shear behavior of externally prestressed concrete beams, the researches mainly focused on simply supported beams. To study the effects of joints and large negative moments on shear behavior of segmental externally prestressed concrete continuous beams, a series of cantilever beam specimens were designed to simulate the negative moment regions in continuous beams. And then, the crack developing, failure modes and mechanical behavior of specimens with different shear span to effective depth ratios, joint types, joint locations and ratios of internal to external tendons were investigated in this experimental study. The test results show that failure cracks of segmental specimens are web shear cracks, whose locations and inclination angles are independent of joints, and eventually the two parts of specimens separated by failure cracks move relatively along the cracks suddenly. The results also reveal that the deflections of segmental specimens after cracking develop very quickly, and the stress increments of prestressing tendons reach 20%∼24% of the tensile strength, which are larger than those of monolithic specimens. In addition, shear strength provided by concrete effects in regions near interior supports of continuous beams is lower than that in regions near supports of simply supported beams, and the contributions of the stirrup and prestressing tendon to the shear strength are 14%∼21% and 8%∼18%, respectively, in which the contribution of stirrup is greater than that of simply supported beams.

Select this Article		Nondestructive Bridge Deck Testing with Air‐Coupled Impact‐Echo and Infrared Thermography Seong‐Hoon Kee, Taekeun Oh, John S. Popovics, Ralf W. Arndt, and Jinying Zhu Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000350 Posted ahead of print 2 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract Two different non‐destructive test (NDT) methods, air‐coupled impact‐echo (IE) and infrared (IR) thermography are evaluated on a full‐scale simulated reinforced concrete bridge deck containing simulated delamination and cracking defects. The IE data are presented as 2‐D frequency maps and spectral B‐scan lines. The IR data are presented as temperature maps on the concrete surface. The lateral boundaries of the detected delaminations are also indicated on the images. The results obtained from each of the individual NDT methods show reasonably good agreement with most of the actual defects. The advantages and limitations of each method to characterize defects are discussed. The consistency and sensitivity of each method are also investigated. Finally, a simple data fusion technique is proposed to improve effectiveness of the individual test data. Findings from this study demonstrate that the combination of air‐coupled IE and IR thermography tests is a practical option for consistent and rapid in‐situ evaluation of reinforced concrete bridge decks.

Select this Article		A Test‐Bed for Structural Health Monitoring of Long‐Span Suspension Bridges Y. L. Xu, F. ASCE, X. H. Zhang, S. Zhan, X. J. Hong, L. D. Zhu, Y. Xia, and S. Zhu, M. ASCE Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000349 Posted ahead of print 2 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract Comprehensive structural health monitoring systems have been developed and installed in several long‐span suspension bridges around the world, aiming to monitor structural health conditions of the bridges in real time. Nevertheless, many key issues remain unsolved, such as how to take full advantage of the health monitoring system for effective and reliable damage detection of these complex structures. An innovative test‐bed was therefore established in a laboratory to allow researchers to re‐create rational damage scenarios, to apply different sensors and sensing networks, and to test various damage detection algorithms. The design principles of the laboratory‐based test‐bed are first introduced in this paper. The paper will then outline the design and setup of a physical model for a long‐span suspension bridge which will consider various damage scenarios. Geometric measurements and modal tests were subsequently carried out to identify its geometric configuration and dynamic characteristics, respectively. The finite element modeling of the physical bridge model was finally established using a commercial software package, which was followed by a finite element model updating using the measured modal properties. This test‐bed, comprising of the delicate physical model and the updated finite element model of a long‐span suspension bridge, could solve a benchmark problem for the structural health monitoring of long‐span suspension bridges.

Select this Article		The Basic Performance of the Composite Deck System Composed of Orthotropic Steel Deck and Ultra‐Thin RPC Layer Xudong Shao, Ph.D., Dutao Yi, Zhengyu Huang, Ph.D., Hua Zhao, Ph.D., Bin Chen, and Menglin Liu Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000348 Posted ahead of print 2 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract Fatigue damage in the conventional orthotropic steel bridge deck system poses a formidable challenge to bridge engineers all over the world, with ever‐increasing heavy traffic volumes and higher wheel loads over the past decade. An effective solution might be to enhance the stiffness of the bridge deck to reduce the fatigue stress amplitude of its components. This paper proposes an innovative composite bridge deck system, which consists of an orthotropic steel deck stiffened with a 45‐mm reactive‐powder‐concrete (RPC) layer. Based on the analysis of HuMen Bridge (a suspension bridge with conventional orthotropic steel bridge deck system with span length of 888 m) and two types of full‐scale model tests, a comparison investigation is conducted between a conventional orthotropic deck system where the asphalt wearing course has been ignored and the proposed orthotropic deck system that includes an integral concrete wearing course, and the proposed composite bridge deck system proves to be considerably effective in reducing the stress range caused by service vehicle loads when applied to long‐span steel suspension bridges. The thin RPC layer can be reliably integrated with the deck plate through stud shear connectors; and no shrinkage cracking occurs on the surface of RPC layer which is cast on the deck plate. The fact that tensile stress of the RPC layer is up to 42.7 MPa before cracking occurs demonstrates that cracking will not appear in RPC layer under the service vehicle loads. The analysis, which is investigated on the premise that the dead load weight of the bridge deck of HuMen Bridge is approximately the same for the two different deck systems, demonstrates that the stress of the orthotropic steel deck is significantly reduced with the application of the proposed composite deck system. The analysis with three‐dimensional finite element model indicates that the transverse tensile stress of the deck plate is reduced by 71%, while that of the connection between the deck plate and the longitudinal troughs by 72%. This concludes that the risk of causing fatigue cracks of the steel bridge deck system can be considerably reduced during the entire life cycle of the bridge.

Select this Article		Synchronization among Pedestrians in Footbridges Due to Crowd Density Roberto Leal Pimentel, Moacir Carlos Araújo, Junior, Halane Maria Braga Fernandes Brito, and José Luis Vital de Brito Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000347 Posted ahead of print 1 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract Crowding is a critical condition for footbridges that are prone to vibration problems due to pedestrian loads. Synchronization of pedestrian movements has been identified as the cause of the excessive lateral vibration in some footbridges. Two conditions have been identified to be the cause of synchronization: increase in crowd density; and pedestrian‐structure interaction. The former would be related to the onset of the phenomenon; the latter takes place after structural vibration reaches a certain level. This paper focuses on the former condition. A test program to investigate whether this condition occurs was carried out for a range of pedestrian densities, complementing data previously published on this subject. The head movement of pedestrians walking both in groups and in a flow were recorded by a video camera and the examination of the video indicated no synchronization due to densification. However, it was observed that the lateral sway of the pedestrians' body increased with the increase of density. By employing an existing model of an inverted pendulum to estimate lateral forces applied by a pedestrian and using the collected data as input to the model, a steady increase of lateral force due to the rise in density was observed; it reached a 104% increase for a density of 1.8 pedestrians/m² when compared to the force applied in unrestricted walking condition.

Select this Article		Nonlinear Seismic Response and Parametric Examination of Horizontally Curved Steel Bridges Using 3‐D Computational Models Junwon Seo, Ph.D., EIT and Daniel G. Linzell, Ph.D., P.E., F. ASCE Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000345 Posted ahead of print 23 November 2011 Full Text: \| Download PDF
	+ -	Show Abstract The seismic behavior of horizontally curved, steel, bridges is more complex than straight bridges due to their curvature and other parameters. Studies that attempt to develop methods to efficiently predict their seismic response have been somewhat limited to date. A computational modeling approach was examined to assist with understanding the seismic behavior of these bridges. The computational, three‐dimensional (3‐D) bridge models consisting of the concrete deck, steel girders, cross‐frames, pier columns and caps, and the abutments and footings were created in OpenSees and examined for accuracy via application to a representative, three‐span continuous, curved, steel, plate girder bridge in Pennsylvania. Sensitivity studies in the form of tornado analyses were also carried out to investigate the influence of critical curved bridge parameters on seismic response using a group of representative bridges. Each representative bridge was subjected to an ensemble of synthetic ground motions and seismic response was examined. Results from the sensitivity study indicated a 17% to 22% variation in maximum bearing and abutment deformations, column curvature ductility and cross‐frame axial forces parameters for the range of bridge radii and span numbers that were investigated.

Select this Article		Performance‐Life‐Cost Based Maintenance Strategies Optimization for Reinforced Concrete Girder Bridges Jinsong Zhu and Boqi Liu Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000344 Posted ahead of print 23 November 2011 Full Text: \| Download PDF
	+ -	Show Abstract This technical note presents a maintenance strategy optimization method for reinforced concrete (RC) girder bridge by considering the performance indicators, service life and life‐cycle maintenance cost as criteria. The condition and reliability indices are defined as performance indicators. The deteriorated processes of performance indicators with and without maintenance actions are described as multi‐linear models. The life‐cycle maintenance planning optimization of deteriorating bridges is formulated as a multi‐objective problem to be solved by an improved non‐dominated sorting genetic algorithm with controlled elitism (NSGA‐II). Condition index, reliability index, service life and life‐cycle maintenance cost of bridge are considered as four separate objective functions. A simply supported RC girder bridge is analyzed as an application example to demonstrate the usefulness of the proposed procedure.

Select this Article		Live‐Load and Shear Connection Testing of Full Scale Precast Bridge Panels Travis R. Brackus, M. ASCE, Paul J. Barr, M. ASCE, and Wesley Cook, M. ASCE Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000343 Posted ahead of print 19 November 2011 Full Text: \| Download PDF
	+ -	Show Abstract This paper describes an investigation to quantify the behavior of a precast deck system. As part of this investigation, a live‐load test was performed on a steel I‐girder bridge made with Accelerated Bridge Construction (ABC) precast deck panels. It was found that the bridge was behaving compositely in some locations and non‐compositely in others. When the bridge was decommissioned, a two girder specimen was salvaged and transported to Utah State University (USU) for shear capacity testing. The primary shear failure mechanism was found to be buckling of the girder web. A nonlinear finite‐element analysis (FEA) was conducted using ANSYS that was found to replicate the experimental behavior and reproduce the failure mechanism and magnitude. It was concluded that the effect of the noncomposite behavior on the ultimate shear capacity was a reduction of approximately 8.0%. The measured ultimate capacities were compared to estimates calculated according to procedures in the AASHTO LRFD Specifications. When using to the specified steel strength, the code predicted shear resistance ranged from 8.0% higher to 0.7% lower.

Select this Article		Markovian Bridge Maintenance Planning Incorporating Corrosion Initiation and Non‐Linear Deterioration A. J. O'Connor, E. Sheils, Denys Breysse, and Franck Schoefs Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000342 Posted ahead of print 19 November 2011 Full Text: \| Download PDF
	+ -	Show Abstract For some materials such as reinforced concrete there is an initiation phase of deterioration where aggressive agents such as chlorides diffuse into the concrete cover. It is necessary to model this initiation time when attempting to determine the optimal maintenance strategy for whole life cost associated with a structure. It has been recommended in the literature that Markov chain models should be further improved within maintenance management systems to take initiation time into consideration. Many existing bridge management systems (BMS) such as BRIDGIT and Pontis use Markovian based maintenance management to simulate the propagation phase of deterioration and repair of structures over time. It is therefore useful to continue this progress through incorporation of an initiation phase in relation to the development of Markovian based maintenance management, which can lead to an improvement in BMS which are already in place. The incorporation of the initiation phase into deterioration modeling can affect the frequency of inspections, repairs and failures, and hence the expected cost over the remaining lifetime of the structure. On this basis, this issue was addressed as part of this study. A maintenance management model has been further developed to take this two step deterioration process (i.e. initiation and propagation) into account. This allows owners/managers of bridges to compare the efficiency of different maintenance strategies in terms of both the initiation phase and the propagation phase of deterioration, to determine the optimum maintenance strategy for the structure or group of structures being considered. The capabilities of the developed methodology are demonstrated using a practical example.

Select this Article		Structural Analysis and Load Test of a 19^th Century Iron Bowstring Arch‐Truss Bridge Cristopher D. Moen, M. ASCE, Elaine E. Shapiro, M. ASCE, and Julia Hart, M. ASCE Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000341 Posted ahead of print 19 November 2011 Full Text: \| Download PDF
	+ -	Show Abstract A structural study examines the oldest remaining metal bridge in the Commonwealth of Virginia, a wrought iron bowstring arch‐truss, designed and manufactured by the King Iron Bridge Company. Finite element analysis is used to evaluate interaction between arch and truss, and the results are compared to field measurements from a live load test. The study reveals that diagonal truss elements decrease arch bending by distributing concentrated vertical loads along the arch toward the abutments in a way consistent with that of modern network arch bridges. With truss diagonals absent, vertical bridge deck deflection doubles. Underslung portal frames provide lateral stiffness to the arch, an innovation that accommodated a shallow arch profile conducive to transportation and erection.

Select this Article		Response of Seismic‐Isolated Bridges in Relation with Intensity Measures of Ordinary and Pulse‐Like Ground Motions Özgür Avşar and Gökhan Özdemir Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000340 Posted ahead of print 19 November 2011 Full Text: \| Download PDF
	+ -	Show Abstract This study concentrates on the efficiency of numerous ground motion intensity measures (IMs) to be used in estimating the response of seismic‐isolated bridges (SIBs). Efficiency of commonly used IMs was investigated through their correlation with maximum isolator displacement (MID) obtained from nonlinear dynamic analyses. Two sets of ground motions, classified as “ordinary” and “pulse‐like”, were employed in nonlinear dynamic analyses of SIBs. In the analyses, varying isolation parameters such as isolation period, T, and the characteristic strength of isolator, Q_d/W, were studied. Sensitivity to varying T, and Q_d/W as well as effect of ground motion type on the correlation of IMs with MID of SIBs were examined. In order to improve the correlation of existing IMs, modified IMs were proposed. The results revealed that isolation period has a pronounced effect on the correlation of IMs with MID of SIBs especially for pulse‐like GMs. Among the investigated IMs, modified velocity spectrum intensity appears to have the strongest correlation with MID of SIBs for a wide range of isolation parameters and ground motion type.

Select this Article		Safety Assessment of Masonry Arch Bridge: Field Testing and Simulations Kishen J. M. Chandra, A. M. ASCE, Ananth Ramaswamy, A. M. ASCE, and C. S. Manohar Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000338 Posted ahead of print 17 November 2011 Full Text: \| Download PDF
	+ -	Show Abstract The safety of an in‐service brick arch railway bridge is assessed through field testing and finite element analysis. Different loading test train configurations have been used in the field testing. The response of the bridge in terms of displacements, strains and accelerations are measured under the ambient and design train traffic loading conditions. Non‐linear fracture mechanics based finite element analyses are performed in order to assess the margin of safety. A parametric study is done to study the effects of tensile strength on the progress of cracking in the arch. Furthermore, a stability analysis to assess collapse of the arch due to lateral movement at the springing of one of the abutments which is elastically supported is carried out. The margin of safety with respect to cracking and stability failure is computed. Conclusions are drawn with some remarks on the state of the bridge within the framework of the information available and inferred.

Select this Article		Critical Speed and Resonance Criteria of Railway Bridge Response to Moving Trains Lei Mao and Yong Lu, F. ASCE Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000336 Posted ahead of print 5 November 2011 Full Text: \| Download PDF
	+ -	Show Abstract The dynamic response of railway bridges to moving trains is complicated due to the involvement of the moving loads as well as the moving masses. Among various response characteristics, the bridge resonance is of particular interest in terms of the structural effect and safety of the bridge. As far as the global bridge response is concerned, it is generally understood that when one of the apparent trainload excitation frequencies coincides with the fundamental natural frequency of the bridge, resonance could occur. However, such a general criterion is of little practical use due to the fact that a typical trainload would involve numerous apparent frequencies (at equal intervals); consequently for a given bridge (natural frequency) there could be many train speeds that satisfy the above resonance condition. Therefore, it is necessary to establish the relative severity of the resonance associated with each resonance scenario. This paper presents the development of a new resonance severity indicator, called Z‐factor, for the assessment of the resonance effect. It is found that the resonance severity is essentially governed by the ratio between the bridge and carriage lengths. When the carriage mass is significant, the same Z‐factor will apply, however the underlying resonance speeds will change due to the altered natural frequency of the bridge‐train system. Numerical results demonstrate that the proposed methods are effective for the determination of the resonance effects associated with the potential resonance speeds.

Select this Article		Integral Bridge Abutment‐to‐Approach Slab Connection Brent M. Phares, Ph.D., P.E., M. ASCE, Adam S. Faris, Lowell Greimann, Ph.D., P.E., F. ASCE, and Dean Bierwagen Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000333 Posted ahead of print 27 October 2011 Full Text: \| Download PDF
	+ -	Show Abstract This paper presents the findings of a performance investigation of two approach slabs (a cast‐in‐place slab and a precast panel slab) integrally connected to two parallel bridges. The goal of using the integral connection is to eliminate the “bump at the end of the bridge”. To measure the performance, a long‐term structural monitoring system consisting of various vibrating wire transducers was installed. From the year‐long monitoring the following general conclusions were made: (1) the integral connection functions well with no observed distress or relative movement between the approach slab and bridge; (2) most of the force at the integral connection is induced by forces at the pavement/approach slab expansion joint; (3) the observed responses generally followed an annual cycle with short term ratcheting patterns also apparent.

Select this Article		Behavior of RC T‐Beams Strengthened in Shear with CFRP under Cyclic Loading Sang‐Wook Bae, A. M. ASCE, Michael Murphy, Amir Mirmiran, F. ASCE, P.E., and Abdeldjelil Belarbi, F. ASCE, P.E. Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000332 Posted ahead of print 27 October 2011 Full Text: \| Download PDF
	+ -	Show Abstract This study investigated the shear performance of RC beams strengthened in shear with externally bonded carbon fiber reinforced polymer (CFRP) strips, subjected to a cyclic loading for 2 million cycles at 2 Hz. The stress level in the stirrups due to the cyclic loading used in this study was higher than those typically used in fatigue studies, which could cause the yielding of some stirrups from the beginning of cyclic loading. This was done to reflect the fact that many RC beams in need of shear strengthening do not meet the minimum stirrup requirement for the new and increased shear demand. The experimental results obtained in this study and the comprehensive review on the existing literature showed that RC beams strengthened in shear with externally bonded CFRP could survive 2 million cycles of cyclic loading without failure. Furthermore, the residual shear strength of the FRP strengthened beam appeared to be greater, albeit slightly, than the static shear strength of the un‐strengthened control beam. This study's results also suggested that limiting the interfacial stress in CFRP strip to less than 1.5 MPa or 25% of its ultimate interfacial strength would increase fatigue life by avoiding debonding of CFRP strips.

Select this Article		Fatigue Behavior of Welded T‐Joints with CHS Brace and CFCHS Chord under Axial Loading in the Brace Ke Wang, Le‐Wei Tong, Jun Zhu, Xiao‐Ling Zhao, and Fidelis R. Mashiri Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000331 Posted ahead of print 27 October 2011 Full Text: \| Download PDF
	+ -	Show Abstract The welded truss composed of circular hollow section (CHS) braces and concrete‐filled circular hollow section (CFCHS) chords is a new kind of structural system which has been increasingly applied in large span arch bridges in China. It is necessary to have a good knowledge of fatigue strength of the welded CHS‐to‐CFCHS joints for the design of this kind of composite bridges. This paper reports on a series of tests on welded CHS‐to‐CFCHS T‐joints subjected to axial cyclic fatigue loading in the brace. Eleven joints were designed to investigate various influence factors such as different non‐dimensional geometric parameters of circular hollow sections and different concrete strength grades. The quality of welds connecting brace and chord members were examined using the magnetic particle and radiographic inspection methods respectively. Hot spot stress distributions at both the crown and saddle positions in brace and chord members were determined by means of linear and nonlinear extrapolation methods. During the fatigue testing process, the number of cycles relating to several stages of failure, the crack initiation positions, crack propagation patterns and the final failure modes were recorded. Fatigue strength of the CHS‐to‐CFCHS T‐joints was compared with that of CHS‐to‐CHS T‐joints. It is concluded that the CHS‐to‐CFCHS T‐joints have much lower stress concentration factor and consequently have better fatigue strength than the CHS‐to‐CHS T‐joints, on the condition of both kinds of joints with the same non‐dimensional geometrical parameters and nominal stress in the brace. The S_rhs — N_f curves in CIDECT guidelines used for CHS‐to‐CHS joints are not appropriate for the reliable fatigue assessment of CHS‐to‐CFCHS T‐joins based on the current test data.

Select this Article		Multiple Presence Factor for Truck Load on Highway Bridges Gongkang Fu, Lang Liu, and Mark D. Bowman Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000330 Posted ahead of print 24 October 2011 Full Text: \| Download PDF
	+ -	Show Abstract Trucks may simultaneously appear on a highway bridge in the same lane or different lanes, which represent the governing load for short and medium span bridges. In practice specifications, the multiple presence factor (MPF) to cover these simultaneous loads was developed using intuition or models without support of measured weight data of trucks in motion. This paper presents a research effort of deriving MPF based on weigh‐in‐motion (WIM) truck data, for both the strength and fatigue limit states, including about 68 million trucks gathered for 436 months and from 43 sites of California, Oregon, Michigan, and New York. The resulting MPFs are proposed in this paper, as functions of bridge span length, truck traffic volume, and number of lanes available. They show that the code specified MPF values are conservative and sometimes over‐conservative by 400% or more, which may have caused too high requirements for load rating existing bridges, especially for shorter spans and/or low truck traffic. The recommended MPF may be considered to be adopted in specifications for highway bridge design and evaluation. This paper also presents a new truck‐by‐truck analysis approach for understanding the load effect of trucks in motion, taking advantage of increasingly available WIM data of large quantity to avoid unsupported assumptions in live load modeling.

Select this Article		Analysis of Eccentrically Loaded Adjacent Box Girders Jarret L. Kasan and Kent A. Harries Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000329 Posted ahead of print 24 October 2011 Full Text: \| Download PDF
	+ -	Show Abstract Research has shown that exterior girders of adjacent box beam (AB) bridges act compositely with their barrier wall and curb slab assemblies resulting in a highly asymmetric cross section. Additionally, impact damage from vehicle collision often severs or exposes strands in the exterior soffit corner of exterior girders. These effects individually (and more so in combination) have the effect of rotating the neutral axis of the girder resulting in significant, unaccounted‐for biaxial flexure. Common structural rating practices analyze the member about its horizontal axis, neglecting the effects of neutral axis rotation and thus overestimate the actual capacity of the member. A parametric study which analyzed the effects of varying levels of damage to eight prototype AB girders was conducted; in all, 106 analyses were carried out. From this study, a relationship is proposed to determine the capacity of an AB beam subject to asymmetric loading which includes the composite behavior of the barrier wall assembly and the effect of prestressing strands lost due to damage to the girder. This relationship is based on easily obtained capacity predictions and is shown to result in predictions of capacity having average absolute error less than 6%. This study also examines, in the context of complete AB bridges, the potential for in‐service loading to exceed assumed design loads.

Select this Article		Environmental Life Cycle Assessment of Bridges Johanne Hammervold, Marte Reenaas, and Helge Brattebø Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000328 Posted ahead of print 24 October 2011 Full Text: \| Download PDF
	+ -	Show Abstract This paper presents a detailed comparative environmental life cycle assessment (LCA) case study of three built bridges in Norway. In order to encompass a wide scale of bridge designs, the analysis dealt with a steel box girder bridge, a concrete box girder bridge and a wooden arch bridge. This study presents the first LCA of road bridges using a standardized bridge classification. The LCA includes a wide range of pollutants and a high level of detail in life‐cycle material and energy consumption. Findings here and from earlier LCAs on bridges are together used as bases for general recommendations on performance of LCAs on bridges. The study shows that it is the production of materials for the main load carrying systems (i.e. the bridge superstructure) and the abutments that accounts for the main share of the environmental impacts as these parts require large quantities of materials, with a limited number of materials being the important ones. The construction phase accounts for relatively less impacts. The use phase contributes more significantly, mainly due to resurfacing with asphalt. Use of building equipment and transport of personnel in all the life‐cycle phases are of minor importance, as also is the use of formwork, mastic, blasting and the end‐of‐life incineration of wood. The environmental issues global warming, abiotic depletion and acidification are found to be the most important given the assumptions made in this study. A comparison of the three bridges shows that the concrete bridge alternative performs best environmentally on the whole, but when it comes to global warming, the wooden bridge is better than the other two. The results support the idea that it is possible to decide upon environmentally‐effective design alternatives, at a fair level of accuracy, at different stages of the bridge design process, a target that is now becoming more and more emphasised in the bridge engineering sector.

Select this Article		CPT‐Based Ultrasonic Probe for P‐Wave Reflection Imaging of Embedded Objects Joseph Coe, A. M. ASCE and Scott J. Brandenberg, M. ASCE Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000327 Posted ahead of print 14 October 2011 Full Text: \| Download PDF
	+ -	Show Abstract An ultrasonic P‐wave reflection imaging probe is developed and utilized to non‐invasively image the geometry of a deep foundation supporting a bridge pier. The source ultrasonic transducer emits compressive waves into saturated soil that subsequently transmit to and reflect back from an embedded object, and the receiver transducer measures the reflections which are used to construct an image. The components of the system, including the custom transducer probe and data acquisition hardware, were integrated with the nees@UCLA cone penetration testing (CPT) truck. Some fundamentals of propagation of ultrasonic waves in soil are presented first, including transducer directivity, effects of unsaturation, the size of the internal scale of the soil, and transducer coupling. The system components are then presented, followed by field testing. The probe successfully imaged a pile foundation in very soft saturated clay, but not in stiffer and/or unsaturated soils. The probe could be very useful for non‐destructive quality assurance of structural elements constructed in‐situ in soft saturated soils.

Select this Article		Automatic Delamination Detection of Concrete Bridge Decks Using Impact Signals Gang Zhang, Ronald S. Harichandran, and Pradeep Ramuhalli Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000326 Posted ahead of print 14 October 2011 Full Text: \| Download PDF
	+ -	Show Abstract Delamination of the concrete cover above the upper reinforcing bars is a common problem in concrete bridge decks. Acoustic non‐destructive evaluation (NDE) is widely used to detect such delamination due to its low cost, speed, and ease of implementation. The accuracy of traditional acoustic approaches is dependent on the level of ambient noise and the detection process is highly subjective. An automatic impact‐based delamination detection (AIDD) system that was developed is described in this paper. In this system, the traffic noise is eliminated by a modified version of independent component analysis (ICA). Mel‐frequency cepstral coefficients (MFCCs) are then used as features for detection to eliminate subjectivity. The delamination detection is performed by a radial basis function (RBF) neural network. The AIDD system was developed using mixed‐language programming in MATLAB, LabVIEW and C++. The performance of the system was evaluated using data from two bridges and the results were satisfactory.

Select this Article		Bi‐Linear S‐N Curves and Equivalent Stress Ranges for Fatigue Life Estimation Ben T. Yen, Ian C. Hodgson, Y. Edward Zhou, and Brenda B. Crudele Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000325 Posted ahead of print 14 October 2011 Full Text: \| Download PDF
	+ -	Show Abstract With the magnitude of some stress cycles in a live load stress range spectrum being higher than the constant amplitude fatigue limit (CAFL) of a structural detail, the development of a fatigue crack could be expected. The current procedure in the AASHTO Specifications for fatigue life estimation utilizes an equivalent constant amplitude stress range with the direct extension of the S‐N lines of slope ‐3 to below the CAFL. This approach is conservative but often results in over‐prediction of fatigue damage and under‐estimation of the safe useful life of structural details. A set of bi‐linear S‐N curves with the knee at the CAFL for the AASHTO fatigue strength categories and a slope of ‐4 below has been produced analytically for estimating fatigue life of existing structures subjected to variable live load stresses. This paper provides information regarding the development of the new equivalent constant amplitude stress ranges for the bi‐linear S‐N curves. Results from a few examples are presented. Adoption of the procedure presented herein for fatigue life estimation is recommended.

Select this Article		Performance Evaluation of RC Beams Strengthened with an Externally Bonded FRP System under Simulated Vehicles Loads Wen‐wei Wang, Jian‐Guo Dai, and Kent A. Harries Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000324 Posted ahead of print 10 October 2011 Full Text: \| Download PDF
	+ -	Show Abstract Carbon fibre reinforced polymer (CFRP) sheets can be used to strengthen existing reinforced concrete (RC) bridge girders/decks. The objective of this study is to investigate whether transient vehicles loads present during the installation of CFRP influence the bond performance between the CFRP and the concrete substrate and therefore the consequent strengthening effect. A total of eight RC beams were tested. Two were unstrengthened reference beams; five were strengthened with CFRP sheets while subject to transient loads; the final beam was strengthened with CFRP sheets while subject to only a sustained static load. The test parameters included the amplitude of the transient load, the anchorage length of CFRP sheets, and the reinforcing/strengthening ratio. The transient loads were continued for two days (during CFRP cure) before all five CFRP‐strengthened RC beams were tested to failure in four‐point flexure. The test results were compared to those of the reference beams and the one strengthened under a sustained load. It was shown that a 1 Hz sinusoidal transient load varying between 30% and 50% of the ultimate capacity of the unstrengthened beam during the installation and curing of CFRP sheets does not affect the structural performance of CFRP‐strengthened RC beams. This result demonstrates the applicability of the FRP strengthening technique for bridge girders which are subjected to continuous vehicle loads.

Select this Article		Numerical Simulation of Vortex‐Induced Vibrations of Inclined Cables under Different Wind Profiles Wen‐Li Chen, Hui Li, Jin‐Ping Ou, and Feng‐Chen Li Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000323 Posted ahead of print 7 October 2011 Full Text: \| Download PDF
	+ -	Show Abstract Vortex‐induced vibration of an inclined cable under wind with varying velocity profiles was investigated through computational fluid dynamics numerical simulation. As a complicated fluid‐structure interaction issue, the flow field around the freely oscillating cable was simulated by CFX 11.0, and the cable oscillation as calculated using the Galerkin approach (realized by the additional subroutine, which is embedded into CFX 11.0). The shear stress transport (SST) k—ω turbulent model based on the RANS method was employed to simulate the behavior of turbulent flow in the CFD numerical simulation. The above computational method and turbulent model were validated through comparison the computational results with the wind tunnel test results of a rigid circular cylinder. And then, two inclination angles, 30° and 90°, were chosen for the inclined cable; wind with a uniform velocity profile (velocity profile U) and four types of velocity profiles were used as the inlet velocity conditions. Based on the cable vibration and flow field obtained under wind with varying velocity profiles, characteristics of the cable vibrations and aerodynamic coefficients in the time domain and frequency domain as well as the wake patterns were analyzed. The results indicated that the cable vibration exhibits two types of behavior—single‐mode vibration (uniform wind or the wind with small velocity changes) and multi‐mode vibration (the wind with large velocity changes)—according to the velocity profile over the inclined cable. The single‐mode vibration of the cable exhibited a standing wave response (a chessboard pattern), whereas the multi‐mode vibration exhibited a travelling wave motion (a parallel line pattern). The lift coefficients exhibited similar features as the cable vibration under wind varying velocity profiles. Dominant frequencies of the lift coefficients could be observed over the upper segments of the cable under wind with small velocity changes (or the entire cable length under uniform wind), but a broader frequency band appeared in the lift coefficients over the low segments of the cable under wind with large velocity changes. The wake patterns and vortex shedding lock‐in regions depended on the vibration type (or the wind velocity profiles). The single‐mode vibration had large lock‐in regions (the entire cable length or the upper segments of the cable), and over these regions, the vortex shedding was in phase or synchronous. However, for a multi‐mode vibration (wind with large velocity changes), the vortex shedding is irregular and complicated along the cable axis.

Select this Article		Effect of Pier Section Reinforcement on Inelastic Behavior of Steel I‐Girder Bridges A. Vasseghi Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000322 Posted ahead of print 7 October 2011 Full Text: \| Download PDF
	+ -	Show Abstract This paper presents the results of an analytical study on inelastic behavior of a four‐span continuous composite bridge girder. The objective is to evaluate the effect of pier section reinforcement on strength and ductility of the girder. The reinforcement consists of two pairs of longitudinal ribs bolted to the web of steel sections adjacent to interior piers. Nonlinear finite element analyses are carried out to determine the moment‐curvature characteristic of the pier sections. The results indicate that unreinforced sections fail due to local buckling upon yielding of the compression flange whereas the reinforced sections reach their plastic moment capacity with good ductility. Idealized moment‐curvature curves are developed based on the nonlinear analyses of the sections. The idealized curves are then used to evaluate the behavior of the girder. The results indicate that strength and ductility of the girder improves substantially when the pier sections are reinforced. At failure the maximum vertical deflection of the reinforced girder is about twice the deflection of the unreinforced girder. The ultimate load carrying capacity of the reinforced girder is also significantly larger than that of the unreinforced girder.

Select this Article		In‐Service Condition Assessment of Bridge Deck Using Long‐Term Monitoring Data of Strain Response Y.Q. Ni, M.ASCE, H.W. Xia, K.Y. Wong, and J.M. Ko, F.ASCE Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000321 Posted ahead of print 7 October 2011 Full Text: \| Download PDF
	+ -	Show Abstract Continuous awareness of the evolution of the structural condition of bridge structures is of great value for bridge owners as it allows making informed decisions regarding the maintenance and management of these public facilities. Structural condition assessment via monitoring gains its popularity in recent years because it can provide structural engineers with plentiful information on structural condition through various sensors. A key issue to successful application of monitoring technologies for condition assessment is how to realize meaningful interpretation of monitoring data. In this study, an approach to structural condition assessment of in‐service bridge deck making use of long‐term monitoring data of strain response is proposed and applied to the instrumented Tsing Ma Bridge. The proposed method consists of structural assessment at two levels: (i) deck truss component level, and (ii) deck cross‐section level. As long‐term monitoring data of dynamic strain under in‐service condition physically results from a combination of live loads and environmental variations, a wavelet multi‐resolution decomposition method is first applied to extract live load effects from the raw measurement data. Based on the extracted data, stress response histories are derived and the statistical characteristics (sample means and sample standard deviations) of peak stresses are explored for stress‐level assessment of deck truss components. Dynamic internal forces (axial force, shear force and moment) of the monitored deck sections are subsequently evaluated by synthesizing the internal forces of the corresponding truss members. Then, internal‐force‐level assessment of the deck sections is carried out for various loading conditions such as monsoon, typhoon, with and without railway traffic.

Select this Article		Erratum for “Numerical Simulation of Partial‐Depth Precast Concrete Bridge Deck Spalling” by Young‐Min You, Lesley H. Sneed, and Abdeldjelil Belarbi Young‐Min You, P.E., Lesley H. Sneed, P.E., M.ASCE, and Abdeldjelil Belarbi, P.E., F.ASCE Journal of Bridge Engineering doi:http://dx.doi.org/ Posted ahead of print 8 October 2011 Full Text: \| Download PDF
		Abstract Unavailable

Select this Article		Effect of Concrete Slab on Shear Capacity of Composite Plate Girders under Positive Moments Ardalan Sherafati, Reza Farimani, and Atorod Azizinamini Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000319 Posted ahead of print 6 October 2011 Full Text: \| Download PDF
	+ -	Show Abstract To evaluate the contribution of the concrete slab on shear resistance of composite concrete‐steel plate girders, two tests were carried out on one full‐scale composite plate girder. The tested specimen was loaded to failure under shear load and positive moment. Vertical deflection of the girder and out‐of‐plane deflection of the web panels were monitored during each test. Principal strains and their inclination were obtained by instrumentation of the web, flanges, stiffeners, and the concrete slab. The observed failure mechanism of the tested specimen is presented using the test results. Nonlinear finite element analysis of the tested specimen was carried out and calibrated using the tests results. To study a wider range of composite girders, further finite element models were built with different concrete slab thickness and steel web slenderness. The experimental and analytical results indicate that the ultimate capacity of the tested composite specimen is higher than what it is predicted by the current AASHTO design specifications for a bare steel plate girder.

Select this Article		Strengthening of Slab Action in Transverse Direction of Damaged Deck of Prestressed Box Girder Bridge: A Case Study Durgesh C. Rai, M. ASCE, Srinaganjaneyulu Komaraneni, and Tripti Pradhan Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000318 Posted ahead of print 3 October 2011 Full Text: \| Download PDF
	+ -	Show Abstract The deck slab of a Prestressed Concrete (PSC) box girder bridge serves as an integral part of the structural box section and any damage to the deck may seriously affect the load‐resistance mechanism of the bridge. This paper discusses a case study of a PSC box girder that developed an early damage to the deck due to the poor placement of concrete at the time of construction as established by the in‐situ non‐destructive and core tests. The possibility of total replacement of the top deck was ruled out because of the disruptive and tedious nature of the process, which could endanger the overall stability of the box girder. Strengthening of the deck was performed by installing a series of steel joists at the underside of the deck slab and adding a thin overlay of concrete at the top in order to restore it to the requisite strength. This approach was best suited, for it not only improved the stress distribution in the deck but also maintained the original load resistance mechanism provided by the prestressing arrangement in the girder. The presented scheme was easy to implement and can be used for similar damages occurring to the deck of PSC box girder bridges.

Select this Article		Methods of Calculating Wind Loads on Long‐Span Girder Bridges with Tall Piers and Comparison Yiqiang Xiang and Zhengwei Ye Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000316 Posted ahead of print 29 September 2011 Full Text: \| Download PDF
	+ -	Show Abstract Calculating wind resistance is one important process in the design of highway bridges. The current codes of many countries include different rules and formulas regarding the calculation of wind resistance. In this paper, the transverse‐direction wind loads on long‐span girder bridges with tall piers were calculated using six codes from different countries under various terrain, pier height, and girder length conditions. The pier‐bottom shear force and moment results of transverse wind loads calculated using these six codes were compared to those obtained using the buffeting frequency domain method. Results showed that, in class B terrain, wind load results predicated by China's 2004 general codes for the design of highway bridges and culverts, China's 2004 wind‐resistant design specifications for highway bridges, Japan's 2007 wind resistant design manual for highway bridges, and part two of Britain's 2006 steel, concrete, and composite bridge specifications for loads resembled each other closely. Some difference was found to exist among class A, C, and D terrain. The 2007 AASHTO LRFD bridge design specifications and China's 2001 load codes for the design of building structures showed significant differences from the other four codes on all kinds of terrain. The applicability of the wind load rules in the AASHTO LRFD bridge design specifications to long‐span girder bridges with tall piers merits further discussion. China's wind load calculations of load code for the design of building structures mainly depended on the experience parameters of architectural structures with large dimensions, and had limited applicability to bridge structures. For long‐span girder bridges with tall piers, such as bridges with span length to width or depth ratios exceeding 30 or pier height to transverse width ratio exceeding 10.7, the wind load calculated using these codes was generally underestimated due to the neglect of the effects of aeroelastic forces, which must be taken into account in the design of these kinds of bridges.

Select this Article		A New Beam Element for Incremental Launching of Bridges Rongqiao Xu and Binlei Shao Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000315 Posted ahead of print 29 September 2011 Full Text: \| Download PDF
	+ -	Show Abstract A new beam element has been developed for the static and dynamic analysis of incrementally launched bridges. The element can describe the deformation subjected to a transverse constraint at an arbitrary point on the beam, thus enabling direct simulation of the superstructure with a continuously position‐varying support during the incremental launching of bridges. With this element, we simplify significantly the finite element modeling of launched bridges, and greatly reduce the computational cost. Some numerical examples are given to show the superiority of the proposed element.

Select this Article		Monitoring and Analysis of Abutment‐Soil Interaction of Two Integral Bridges H. Pétursson and O. Kerokoski Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000314 Posted ahead of print 28 September 2011 Full Text: \| Download PDF
	+ -	Show Abstract Field tests of two jointless bridges are presented, focusing on the magnitude and significance of earth pressure behind the abutments. The Haavistonjoki Bridge is a 56 m long, continuous three span bridge. Instrumentation was used to measure the horizontal displacement of an abutment, abutment rotation, abutment pile strains, earth pressures behind the abutments, superstructure displacements, frost depth and air temperature. The measured earth pressures were compared with pressures that had been calculated on the basis of Nordic codes of practice and the Eurocodes pertaining to bridges. The bridge over the Leduån is a single span composite bridge with a cast‐in‐place concrete deck on top of two steel beams. This bridge, spanning 40 m, is slender, with a 1.7 m high superstructure. The bridge was fitted with strain and displacement gauges and short term measurements were made using a loaded truck. The field test results for this bridge were verified with calculations based on an abutment rotation stiffness calculation model developed during the research presented in this paper.

Select this Article		A Nonlinear Analysis for the Lateral Vibration of Footbridges Induced by Pedestrians Zhen Bin, Xie Weiping, and Xu Jian Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000313 Posted ahead of print 26 September 2011 Full Text: \| Download PDF
	+ -	Show Abstract In this paper, the factors and variables which effect the amplitude of the lateral vibration of the footbridge induced by pedestrians in Nakamura's model are investigated in the aspect of nonlinear dynamics. Nakamura' model is based on the motion of equations including coefficients of the rate of a pedestrian's lateral force, the pedestrian density, the rate of synchronized pedestrians, the function G(f_B) describing how pedestrians synchronize with the bridge natural frequency, and the pedestrians' attitude to large vibration amplitude. The important coefficient G(f_B) cannot be decided in this model because of the lack of the data available on the lateral load behaviours of walking people. Nakamura assumed that G(f_B) = 1.0 in his model by considering that pedestrians are most likely to synchronize at the bridge frequency around 1.0Hz. The analysis results presented in this paper demonstrate that the amplitude of the lateral vibration increases with the function G(f_B) increasing. This suggests G(f_B) = 1.0 maybe not the worst case scenario for the lateral vibration of footbridges. Assuming G(f_B) = 1.0 maybe one reason why most of the predicted results of Nakamura are on the large side. Through modifying Nakamura's model, a equation of motion including the time delay of the interaction between the pedestrians and the footbridge is proposed to preferably agree with the measure data. The analysis shows that the amplitude of the lateral vibration of the footbridge decreases with the time delay increasing. The ignored time delay of the interaction between pedestrians and the footbridge in Nakamura's model is another reason resulting in numerical results of Nakamura is bigger than measure data. From the analysis, appropriately increasing time delay of the interaction between pedestrians and the footbridge is a possible way to reduce the lateral vibration induced by pedestrians.

Select this Article		Analysis Model Verification of a Suspension Bridge Exploiting Configuration Survey and Field Measured Data Ho‐Kyung Kim, Ph.D. M.ASCE, Nam‐Sik Kim, Ph.D., Jeong‐Hwan Jang, Ph.D., and Young‐Ho Kim, Ph.D. Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000312 Posted ahead of print 19 September 2011 Full Text: \| Download PDF
	+ -	Show Abstract The conformity between predicted and actual configurations of a suspension bridge is examined through a field survey with the compensation of temperature effects. The tension in the main cable is estimated from the surveyed configuration utilizing force equilibriums at the cable junction nodes. Measured hanger tensions and rigorous dead load information are also incorporated. The as‐built configuration of the bridge shows fairly good agreement with the designed shape. The reproducibility of dynamic properties is also examined for dominant vertical modes. The only tuning in the connection conditions of bearings produces natural frequencies that are in good agreement with measured values.

Select this Article		Detection of Initial Yield and Onset of Failure in Bonded Post‐Tensioned Concrete Beams Salvatore Salamone, M. ASCE, Marc J. Veletzos, P.E., M. ASCE, Francesco Lanza di Scalea, and José I. Restrepo, M. ASCE Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000311 Posted ahead of print 16 September 2011 Full Text: \| Download PDF
	+ -	Show Abstract This paper discusses monitoring of bonded post‐tensioning (PT) concrete elements using the acoustic emission (AE) technique. In particular a statistical pattern recognition technique based on a multivariate outlier analysis is presented to identify initial yielding and the onset of failure. Experimental tests on large‐scale single‐tendon bonded PT concrete beams, subjected to multiple load cycles, will be presented to validate the proposed monitoring system.

Select this Article		Updating Fatigue Damage Coefficient in Railway Bridge Design Code in China Yuling Zhang, Xuezhong Xin, and Xin Cui Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000310 Posted ahead of print 16 September 2011 Full Text: \| Download PDF
	+ -	Show Abstract Railway traffic volumes in China have increased dramatically with the fast development of the Chinese economy in the past 20 years. Load frequency spectra of bridges have also changed as a result. Therefore it is necessary to update the fatigue damage coefficient used in the railway bridge design code accordingly. This paper discusses the updating work that involved a series of analysis and calculation based on the information obtained from a nationwide investigation of different railway lines. The newly updated fatigue damage coefficient has been recommended for the Chinese railway bridge design code.

Select this Article		Structural Identification of a Deteriorated Reinforced Concrete Bridge Yun Zhou, John Prader, Jeffrey Weidner, Nathan Dubbs, Franklin Moon, and A. Emin Aktan Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000309 Posted ahead of print 16 September 2011 Full Text: \| Download PDF
	+ -	Show Abstract Displacement coefficients and profiles have been proposed as objective indices for bridge structural condition evaluation by many researchers. In this paper, experimental data was collected for structural identification (St‐Id) of a deteriorated bridge: (1) static displacement and strain measurements taken under proof‐load level, and; (2) multi‐reference impact test (MRIT) data from one of the spans of a three span, cast‐in‐place reinforced concrete (RC) T‐beam (Smithers) Bridge. MRIT was used to generate the modal data for computation of modal flexibility and displacement profiles. Several significant obstacles were encountered during the St‐Id of the Smithers Bridge including high damping level (which lead to difficulties in identifying and selecting the poles), finite element (FE) model updating challenges, and the correlation of MRIT results with truck load test measurements. The first challenge was addressed through the use of the Complex Mode Indicator Function (CMIF) method of modal identification, which is capable of identifying highly damped modes. Then the updating of the FE model was accomplished using the Strand7 FE analysis package coupled with the MATLAB application programming interface (API). Finally in order to allow for the direct comparison of MRIT and truck load results, two strategies were employed. The first involved the redistribution of truck load force to the MRIT degrees of freedom (DOFs) and the second utilized interpolation functions for modal expansion of the MRIT results to include the truck tire locations. The St‐Id procedure used during this application was designed to mitigate blatant human error and epistemic uncertainty in the data interpretation process. Successful results from MRIT demonstrated the reliability of applications for bridge condition assessment based on impact testing.

Select this Article		Effective Flange Width for Honeycomb FRP Sandwich Bridge Deck‐on‐Steel Girder System with a Mechanical Shear Connector Considering Degrees of Composite Action An Chen, Julio F. Davalos, Adam L. Justice, Gregory K. Michaelson, and Nagavardhana Perisetty Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000308 Posted ahead of print 16 September 2011 Full Text: \| Download PDF
	+ -	Show Abstract Effective flange width is used in bridge engineering to reduce a 3‐D structure to a 2‐D beam analysis. AASHTO Specifications provide provisions solely for effective flange width for concrete decks on steel girders with full‐composite action. In recent years, FRP decks have been increasingly used because of their many advantages. An FRP deck‐on‐steel girder system exhibits either full or partial composite action, depending on the shear connection used to attach the deck to supporting girders. Since no design guidelines are available, the bridge system is often considered as non‐composite, and therefore, the bridge is usually over‐designed. This paper systematically evaluates effective flange width for honeycomb FRP sandwich deck‐on‐steel girder bridge system, accounting for either full or partial composite action, to propose a modified AASHTO equation to calculate the effective flange width. In this paper, a Finite Element (FE) model is first developed to predict effective flange width for FRP deck‐on‐steel girder system with partial composite action based on a proper definition of the effective flange width, which is then verified by testing results of a T‐beam section. The FE model is then used to carry out a parametric study by varying the degree of composite action and stiffness of the bridge deck. Based on the results from the parametric study, a modified AASHTO equation is proposed to calculate the effective flange width. Finally, an example is provided to illustrate the use of the proposed equation. It is concluded that the bridge stiffness and strength can be significantly increased by considering the proper contribution of the FRP deck, which is in contrast to the general impression that, because of the low equivalent modulus of the FRP deck, the contribution of the deck to the bridge system may be neglected, even for full‐composite action.

Select this Article		Modeling Structural Performance of Ultra‐High Performance Concrete I‐Girders Linfeng Chen, Ph.D., P.E., M. ASCE and Benjamin A. Graybeal, Ph.D., P.E., M. ASCE Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000305 Posted ahead of print 7 September 2011 Full Text: \| Download PDF
	+ -	Show Abstract Ultra‐high performance concrete (UHPC) is an advanced cementitious composite material which has been developed in recent decades. When compared to more conventional cement‐based concrete materials, UHPC tends to exhibit superior properties such as increased durability, strength, and long‐term stability. This computational investigation focused on modeling the structural behaviors of UHPC components including prestressed UHPC AASHTO Type II girders. The concrete damaged plasticity model was tailored to model UHPC within a commercially available finite element analysis package. This manuscript focuses on modeling three UHPC I‐girders tested under flexural or shear loading configurations. The concrete damaged plasticity model was demonstrated to replicate both linear and nonlinear structural responses of I‐girders reasonably well. A set of UHPC constitutive properties were developed that facilitate the model replication of the local and global responses observed in the series of physical tests.

Select this Article		Flexural Crack Widths in Concrete Girders Reinforced with High‐Strength Reinforcement Kent A. Harries, Bahram M. Shahrooz, and Amir Soltani Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000306 Posted ahead of print 2 September 2011 Full Text: \| Download PDF
	+ -	Show Abstract The introduction of steel reinforcing bars having yield strengths exceeding 75 ksi (517 MPa) and often approaching 120 ksi (827 MPa) may allow for significant economies to be realized, particularly when used in conjunction with high strength concrete. One implication of the adoption of higher strength reinforcing steel is that reinforcing bar stresses, and therefore strains and consequently crack widths, at service load levels is expected to be greater than when conventional bars (having a yield of 60 ksi (414 MPa)) are used. A study of flexural crack widths of beams reinforced with high‐strength ASTM A1035 reinforcing steel is presented. Discussion focuses on the behavior at loads corresponding to longitudinal reinforcing bar stresses of 36, 60, and 72 ksi (248, 414 and 496 MPa), representing service load levels (i.e., 0.6f_y) for steel having f_y = 60, 100, and 120 ksi (414, 690 and 827 MPa), respectively. Average measured crack widths obtained from a series of flexural beams having reinforcing ratios ranging from 0.007 to 0.023 are found to be below the present AASHTO de facto limits for Class 1 and Class 2 exposure. The demonstrated conservativeness of existing ACI and AASHTO crack control provisions allows present specifications to be extended to the anticipated higher service level stresses associated with the use of high‐strength reinforcing steel.

Select this Article		Full‐Scale Ultimate‐Load Test of a Stress‐Laminated‐Timber Bridge Deck K. Ekholm, R. Kliger, and R. Crocetti Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000304 Posted ahead of print 2 September 2011 Full Text: \| Download PDF
	+ -	Show Abstract A general assumption reported in the literature is that the structural response of a stress‐laminated‐timber bridge (SLT) deck is linear until failure. However, few studies of ultimate‐load tests on timber bridges have been reported. A full scale test of a SLT deck, span 4.9 m and thickness of 270 mm, was performed to obtain deformations at various pre‐stress levels as well as the ultimate load capacity of such a structure. Prior to the ultimate load test, non‐destructive tests (NDT) were performed at three different pre‐stress levels. Load was applied as an axle load positioned both centrically and eccentrically. Deflections were about 10% larger at a pre‐stress level of 300 kPa compared to a pre‐stress level of 600 and 900 kPa. For applied loads larger than 150–250 kN, the deflection of the deck was non‐linear at certain positions. This was most likely due to large concentrated shear forces resulting in interlaminar slip between the laminates. The limit for linearity seems to be dependent on the pre‐stress applied. A pre‐stress of 600 kPa and an eccentrically positioned load was used for the ultimate load test. Failure occurred at a load level of 900 kN. Existing design codes and new procedures in development may be verified and calibrated against results in this paper.

Select this Article		Evaluation of Commercially Available Remote Sensors for Highway Bridge Condition Assessment Khatereh Vaghefi, Renee C. Oats, Devin K. Harris, Theresa (Tess) M. Ahlborn, Colin N. Brooks, K. Arthur Endsley, Christopher Roussi, Robert Shuchman, Joe W. Burns, and Richard Dobson Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000303 \| Cited 1 time Posted ahead of print 1 September 2011 Full Text: \| Download PDF
	+ -	Show Abstract Improving transportation infrastructure inspection methods and the ability to assess condition of bridges has become a priority in recent years as the transportation infrastructure continues to age. Current bridge inspection techniques consist largely of labor‐intensive subjective measures for quantifying deterioration of various bridge elements. Some advanced non‐destructive testing techniques such as ground penetrating radar are being implemented, however little attention has been given to remote sensing technologies. Remote sensing technologies can be used to assess and monitor the condition of bridge infrastructure and improve the efficiency of inspection, repair, and rehabilitation efforts. Most important, monitoring the condition of a bridge using remote sensors can eliminate the need for traffic disruption or total lane closure as remote sensors do not come in direct contact with the structure. The purpose of this paper is to evaluate twelve potential remote sensing technologies for assessing the bridge deck and superstructure condition. Each technology was rated for accuracy, commercial availability, cost of measurement, pre‐collection preparation, complexity of analysis and interpretation, ease of data collection, stand‐off distance, and traffic disruption. Results from this study demonstrate the capabilities of each technology and their ability to address the bridge challenges.

Select this Article		Live Load Analysis of Post‐Tensioned Box‐Girder Bridges Dereck J. Hodson, Paul J. Barr, and Marvin W. Halling Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000302 Posted ahead of print 27 August 2011 Full Text: \| Download PDF
	+ -	Show Abstract This paper presents an evaluation of flexural live‐load distribution factors for cast‐in‐place box girder bridges. The response of a typical box girder bridge was recorded during a static live‐load test. This test involved driving two heavily loaded trucks across the instrumented bridge on selected load paths. The instruments used to record the response of the bridge were strain gages, displacement transducers, and tilt sensors. This measured data was then used to calibrate a finite‐element modeling scheme using solid elements. From this finite‐element model, the theoretical live‐load distribution factors and load ratings for the test bridge were determined and compared to those predicted in the AASHTO LRFD Specifications. A parametric study of cast‐in‐place, box‐girder bridges using the calibrated finite‐element modeling scheme was then used to investigate how different parameters such as span length, girder spacing, parapets, skew, and deck thickness affect the flexural live‐load distribution factors. Based on the results of the parametric study, a new equation that more accurately predicts the exterior girder distribution factor is proposed.

Select this Article		Modeling Structural Performance of 2^nd Generation Ultra‐High Performance Concrete Pi‐Girders Linfeng Chen, Ph.D., P.E., M. ASCE and Benjamin A. Graybeal, Ph.D., P.E., M. ASCE Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000301 Posted ahead of print 27 August 2011 Full Text: \| Download PDF
	+ -	Show Abstract The concrete damaged plasticity model with proposed material properties replicated the observed deflection and strain responses of the three experimentally tested I‐girders and was determined to be consistent for different spans under both flexural and shear tests. In this paper, the CDP model was further tested in modeling the behaviors of a prestressed 2nd generation UHPC pi‐girder. The computational aspects include discussion of the various parameters that influence the accuracy of the model and investigation of the scenarios in the limit that are useful for further optimization of the girder. The CDP model was reconfirmed consistent and reliable in replicating the observed structural response of both the UHPC pi‐girder and a modified structural configuration referred to as the UHPC pi‐girder with joint. The finite element analysis modeling techniques developed herein are expected to be valuable in the future development of additional UHPC structural components.

Select this Article		Bridge Timber Piles Load Rating under Eccentric Loading Conditions Bassem Andrawes, A. M. ASCE and Pablo Caiza Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000300 Posted ahead of print 24 August 2011 Full Text: \| Download PDF
	+ -	Show Abstract This study evaluates the load rating procedure that is currently used in rating timber piles supporting multiple‐span simply supported bridges. For simplicity, these piles are often rated under concentric loads and the effect of bending in the piles is neglected. Recent studies have shown however, that under highly eccentric live loads, the effect of bending moments in the piles are of great importance and could have a dramatic effect on the piles load rating. This paper proposes an alternative structural load rating method for timber piles based on the National Design Specifications which takes the effect of combined compression‐flexure behavior of piles into consideration. This method is used to conduct a parametric study to investigate the effect of several geometric and structural parameters on the load rating of bridge timber piles using 3‐D finite element models of concrete‐deck bridges supported on group of timber piles. The results show that the proposed load rating method produced significantly less ratings for piles with moderate‐to‐high levels of deterioration, as compared to that obtained by the conventional approach. Among the studied parameters, the pile length is found to have the most significant impact on the pile load rating.

Select this Article		Experimental Study on Repair Methods of Corroded Bridge Cables Shunichi Nakamura and Keita Suzumura Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000299 Posted ahead of print 20 August 2011 Full Text: \| Download PDF
	+ -	Show Abstract Cables and hangers of old suspension bridges and stays of cable‐stayed bridges often suffer from steel corrosion. It is important to repair them by proper methods so that corrosion does not progress further. In this paper six repair methods were proposed and applied to cable specimens. Then, the specimens were exposed to severe corrosion environments and the effectiveness of the proposed repair methods was compared. Two different types of test cables were used in this study: parallel wire strands and spiral strands. The first test group used parallel wire strand cables consisting of 19 non‐galvanized steel wires. This aimed at the main cables of suspension bridges. Six repair methods were applied to these cable specimens: coating with zinc or epoxy resin paint or zinc powder paste, filling with epoxy resin or oil, and dehumidification method. Then the specimens were accelerated to corrode in a laboratory for 15 months. By investigating mass loss due to corrosion and appearance during this period, the effectiveness of six repair methods was compared. As for the surface wires, the dehumidification method was the most effective followed by the epoxy resin paint and filling, the zinc powder paste, and the zinc and epoxy resin paint on the surface. The oil filling was not very effective compared with other repair methods. The corrosion of the inside wires was much less than those of the surface wires. The second group test used spiral strand cables consisting of seven galvanized steel wires. This test aimed at hangers of suspension bridges and stays of cable‐stayed bridges. The same repair methods and corrosion acceleration methods were used. By investigating mass loss due to corrosion and appearance of both inside and surface wires during the 16 month period, most of the proposed repair methods were very effective compared with those of not repaired strands. This study proves that, even if cables are corroded, proper repair works are effective in preventing further corrosion.

Select this Article		Response Modification Approach for Safe Extension of Bridge Life Andrew J. Gastineau, S. M. ASCE, Steven F. Wojtkiewicz, M. ASCE, and Arturo E. Schultz, M. ASCE Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000298 Posted ahead of print 13 August 2011 Full Text: \| Download PDF
	+ -	Show Abstract A large portion of highway bridges in the United States are reaching or have reached their intended design lives. To avoid replacing a large number of bridges simultaneously, methodologies to safely extend their lives will be important to help avoid high replacement costs and to schedule bridge replacement over a longer time window. This paper proposes an approach to extend the fatigue life of vulnerable steel bridges through a response modification apparatus, consisting of a mechanical amplifier and a response modification device which provides supplemental stiffness and damping to the bridge. Due to the relatively small deflections encountered under typical service loads, the use of a mechanical amplifier allows for a smaller apparatus and enables a more efficient device to provide adequate response modification forces to the bridge. Herein, the use of a scissor jack as the mechanical amplifier is proposed for use in bridge applications, and its utility in concert with a passive stiffness device is demonstrated by application to a simple beam structure. Reductions in moment ranges of 37 percent and safe life extensions of 300 percent are achieved on a simple beam model with the proposed response modification apparatus.

Select this Article		Determination of 18 Flutter Derivatives of Bridge Decks by an Improved Stochastic Search Algorithm F. Y. Xu, X. Z. Chen, C. S. Cai, and A. R. Chen Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000295 Posted ahead of print 6 August 2011 Full Text: \| Download PDF
	+ -	Show Abstract This paper addresses the determination of the 18 flutter derivatives of bridge decks from three degree‐of‐freedom (3DOF) free vibration data using an improved stochastic search algorithm (ISSA) combined with the unified least‐square (ULS) method. The ISSA is capable of circumventing the local optimum dilemma in pursuing the optimal solution experienced in the traditional ULS method. The validity and accuracy of the ISSA are demonstrated by one numerical example and two long‐span cable‐stayed bridge deck sections. The attractive merit of using different lengths of vertical, torsional and lateral vibration data in flutter derivatives identification is investigated. The identification error and modal participations in flutter are easily examined through a decomposition of modal components from the original vibration data. The underlying complexities in aeroelastic parameter identification are studied and the causes of low accuracy of some flutter derivatives are unveiled. Based on the comparative investigation on the aerodynamic characteristics of typical streamlined and bluff bridge decks, an improved understanding of the coupled bridge flutter is achieved.

Select this Article		Quality Assurance of Measured Response Intended for Fatigue Life Prediction John Leander and Raid Karoumi Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000291 Posted ahead of print 4 August 2011 Full Text: \| Download PDF
	+ -	Show Abstract By in situ measurements, the real distribution of stress ranges caused by service loads can be recorded. Inherent effects in the measured response as disturbance can, however, create puzzles in the interpretation of the result. In large monitoring campaigns, it is not possible to examine the result from every gauge over the whole measured period by visual control. In this paper, an approach for a quality assurance of the measured response is presented based on established statistical methods. The stress range spectra, the product of the monitoring program intended for fatigue assessment, are analyzed. The aim of the analysis is to find deviant spectra and identify corrupt gauges. An additional aspect is the length of the monitoring period, that is the required duration for obtaining a stable result. A case study of a monitored Swedish steel railway bridge is incorporated in the paper to exemplify the approaches. Some statistical distributions for the monitored stress ranges are also presented and incorporated in a fatigue assessment.

Select this Article		Seismic Fragility of Retrofitted Multi‐Span Continuous Steel Bridges in New York A. K. Agrawal, M. ASCE, M. Ghosn, M. ASCE, S. Alampalli, F. ASCE, and Y. Pan Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000290 Posted ahead of print 29 July 2011 Full Text: \| Download PDF
	+ -	Show Abstract Various retrofit measures, such as elastomeric bearings, lead rubber bearings, viscous dampers and jacketing by carbon fibers, are commonly used to improve the seismic performance of multi‐span continuous steel highway bridges. In this paper, we have investigated the effectiveness of these retrofit measures through comparisons of seismic fragility of as‐built and retrofitted multi‐span continuous steel bridges. Both elastomeric and lead rubber bearings reduce fragility of bridge piers significantly through isolation effects. Wrapping of piers by FRP increasing the effective ductility of piers through confinement and shifts the failure mode of a FRP wrapped pier to rupture of FRP at much higher peak ground acceleration. The use of viscous dampers in combination with elastomeric bearings is effective in reducing fragilities because of both pier ductilities and bearing displacements. Hence, all four seismic retrofit strategies are effective in improving safety of bridge components during earthquakes.

Select this Article		A Discussion on Code Formulas for Ship‐Impact Design of Bridges Wang Junjie, Bu Lingtao, and Cao Conghui Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000289 Posted ahead of print 27 July 2011 Full Text: \| Download PDF
	+ -	Show Abstract Four finite element models of ships with deadweight tonnage(DWT) varying from 3,000 to 50,000 tons are developed for numerical collision simulation. The time histories for ship collisions against rigid walls are obtained using the software LS‐DYNA. Equivalent static loading is determined and simplified formulas are developed through a fitting procedure based on the data from the numerical simulations. Codified formulations from AASHTO and other design specifications are compared with the simplified formulas. Geometric effects of bridge foundation on the ship impact force are investigated with an example pile‐cap. A geometric modification factor is proposed for an ideal rectangular block to modify ship impact forces estimated by code formulas.

Select this Article		A Practical Approach for Estimating Distribution Factor for Load Rating: Demonstration on Reinforced Concrete T‐Beam Bridges F. Necati Catbas, H. Burak Gokce, and Mustafa Gul Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000284 Posted ahead of print 6 July 2011 Full Text: \| Download PDF
	+ -	Show Abstract For the analysis of highway bridges, beamline analysis using distribution factor (DF) formulations is commonly used by design offices, DOT engineers and other practitioners as a practical method given in the American Association of State Highway and Transportation Officials (AASHTO) specifications. This approach utilizes bridge span length, beam spacing, beam stiffness and slab thickness to provide an approximation to load distribution instead of using 3D finite element models (FEMs), which are not generally feasible due to considerable time, effort and expertise required for development. In addition, a 3D FEM does not guarantee the as‐is condition of an existing bridge unless it is field‐calibrated with experimental data. So far, field tests and calibrated model development approaches presented in the literature require mainly load tests by closing the bridge to traffic and major instrumentation effort as well as extensive model calibration. In this paper, the authors present a methodology with rapid experimental testing to determine critical parameters for practical analysis of highway bridges. This approach is demonstrated on a reinforced concrete T‐beam bridge population. The authors illustrate that the moment DFs of single span T‐beam bridges can be determined by using skew angle, modal frequency and the flexibility coefficient where frequency and flexibility coefficient can be identified by means of rapid impact test that can be conducted using an impactor, such as a Falling Weight Deflectometer (FWD). To demonstrate the methodology, first, FEMs of 40 single span T‐beam bridges are analyzed to obtain the modal frequency and flexibility coefficients. Second, the maximum moment values of these bridges are obtained using the FEMs and simple beam analyses under HL‐93 truckload. Third, a multiple regression analysis is conducted to generate an equation to determine the moment DF (i.e. the ratio of FEM response to beam analysis) as a function of modal frequency, flexibility and skew angle. This equation is then verified by using additional FEMs, where moment approximation to FEM results with the new approach is 6% whereas this approximation is in the order of 30% with the conventional beamline analysis given in the AASHTO code. Finally, this approach is demonstrated by using experimental data from four real life bridges for the computation of moment values as well as the load ratings. It is seen that the new approach can conservatively accommodate live load increase for the four existing bridges.

Select this Article		Blast Resistance of Steel Orthotropic Bridge Decks Jin Son and Abolhassan Astaneh‐Asl Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000283 Posted ahead of print 2 July 2011 Full Text: \| Download PDF
	+ -	Show Abstract The main objectives were: (a) to study response of bridge decks to blast effects resulting from an explosion on the deck; and (b) to develop efficient technologies and systems that can be used in design and construction of such bridges to enable the bridges to survive blast attacks without collapse. During the first part of the study, and in order to understand actual behavior of orthotropic decks subjected to blast loads, typical steel orthotropic decks used in long span cable‐supported bridges were modeled using MSC. Dytran nonlinear finite element analysis software and the models were subjected to simulated explosion occurring on the deck. The parameters that varied in the analyses were the size of explosive device in terms of equivalent TNT, the axial compressive force present in the deck and high strain rate mechanical properties of the material of the steel used in the orthotropic deck. By conducting dynamic analyses, behavior of the orthotropic decks under blast loads was established and their failure modes were identified. During the second part of the study, new and effective blast‐resistant technologies such as “fuse system,” were developed. In this system, in order to limit the effect of blast to a localized area of the bridge and to prevent catastrophic progressive collapse of the span, special “fuses” have been developed to be placed between two deck segments.

Select this Article		Structural Behaviour of Inferior‐Deck Spatial Arch Bridges with Imposed Curvature Marta Sarmiento‐Comesías, Ana M. Ruiz‐Teran, and Angel C. Aparicio Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000282 Posted ahead of print 29 June 2011 Full Text: \| Download PDF
	+ -	Show Abstract Spatial arch bridges have a significant out of plane behaviour which we must control even under vertical loads. In some designs, the centre line of the arch may not even lie within a plane. The present study focuses on the structural behaviour and the effect of the geometrical configurations of inferior‐deck arch bridges with imposed curvature. In this type of spatial arch bridges the arch and the deck centroid lines are both contained in the same vertical cylinder. The aim of the study is to propose the most appropriate design for controlling the out‐of‐plane response. A simple analytical model representing the stiffness of the arch, the deck and a hanger, allowed us to determine the main variables that control the behaviour of the system. Afterwards, we analyzed a series of linear 3D frame FE models of the complete bridge. The study demonstrates that non‐planar arches can be approximated by inclined planar arches. Parametric analyses have led to recommending a set of relevant design criteria for these bridges.

Select this Article		Behavior of Segmental Precast Post‐Tensioned Bridge Piers under Lateral Loads Haitham Dawood, Mohamed ElGawady, and Joshua Hewes Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000252 Posted ahead of print 26 May 2011 Full Text: \| Download PDF
	+ -	Show Abstract Segmental precast post tensioned (SPPT) bridge pier is an economic re‐centering structural system. Understanding the seismic behavior of a SPPT system is an important step towards its application in high seismic zones. This manuscript presents a detailed three dimensional finite element (FE) model developed using the ABAQUS platform. A brief description and discussion of cyclic tests on eight large scale SPPT piers was also presented. Four of the piers were constructed and tested to a predefined degree of damage. Then, these piers were retrofitted and re‐tested. The FE models developed and presented in this paper predicted the backbone curves of the piers that were tested directly after construction with an average error of 7% for drift angles smaller than 2.5%. For drift angles greater than 2.5%, the average error reached 13%. For piers that were retrofitted and re‐tested, the error in predicting the backbone curve depends on the state of damage before the re‐test. When preexistent micro‐cracks were not severe, the FE models were able to predict the backbone curves with an error of approximately 12%. However, the error significantly increased and reached a value of approximately 31% when the preexistent micro‐ cracks were severe. In addition, the FE models confirmed the experimental observations and showed that the SPPT pier system is able to withstand large lateral drift angles with minimal damage. Finally, sensitivity analyses using the FE model showed that the model is sensitive to the softening behavior of the concrete material constitutive law.

Select this Article		Buckling Behavior of Steel Bridge I‐Girders Braced by Permanent Metal Deck Forms O. Ozgur Egilmez, Todd A. Helwig, and Reagan Herman Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000276 Posted ahead of print 26 May 2011 Full Text: \| Download PDF
	+ -	Show Abstract Permanent metal deck forms (PMDF) are often used in the bridge industry to support the wet concrete and other loads during construction. Although metal formwork in the building industry is routinely relied upon for stability bracing, the forms are not permitted to be considered for bracing in the bridge industry despite the large in‐plane stiffness. The forms in bridge applications are typically supported on cold‐formed angles that allow the contractor to adjust the form elevation to account for changes in flange thickness and differential camber between adjacent girders. Although the support angles are beneficial towards the constructability of the bridge, they lead to eccentric connections that substantially reduce the in‐plane stiffness of the PMDF systems, which is one of the reasons the forms are not relied upon for bracing in bridge applications. This paper documents the results of a research investigation focused on improving the bracing potential of bridge deck forms. Modifications to the connection details were developed to improve the stiffness and strength of the forming system. The research included buckling tests on a 15 m (50 ft.) long twin girder system with PMDF for bracing. In addition to demonstrating the behavior of the bracing systems, the twin‐girder tests were also used to validate computer models of the bracing systems that were used for parametric FEA studies. Buckling test results] demonstrated that modified connection details make PMDF systems a viable bracing alternative in steel bridges that can significantly reduce the number of cross‐frames or diaphragms required for stability bracing of steel bridge I‐girders during construction.

Select this Article		Influence of Skew Angle on Continuous Composite Girder Bridge Gholam reza Nouri and Zahed Ahmadi Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000273 Posted ahead of print 26 May 2011 Full Text: \| Download PDF
	+ -	Show Abstract The design of skewed bridges is becoming more customary in the engineering community. In this paper, the effect of skew angle on continuous composite girder bridges is presented using the 3‐D finite‐element analysis (FEA). For this aim, 72 models of two‐span bridges with different span ratios (N=1, 1.55, and 1.82), skew angles (0–60°) and different arrangements of intermediate transverse diaphragms are analyzed. All models are subjected to American Association for State Highway and Transportation Officials (AASHTO) HS20‐44 loading. Results for skewed bridges are compared to the reference non‐skewed bridge, as well as AASHTO Standard Specifications and AASHTO LRFD Specifications. Results show that, as the skew angle increases, the support moment in interior and exterior girders decreases rapidly. It decreases about 10% when skew angle is less than 20° and reaching 33% for 45°. The shear force increases in pier support at the exterior girders and decreases at the interior ones with increasing skew angle. For exterior girders, the ratio of shear force increases up to 1.3 for skew angle of 45°. The AASHTO Standard Specifications overestimate the maximum bending moment by 20% for skew angle of 30° and N=1, and 50% for 45°. The overestimation of shear force is about 10% for skew angle of 45°. The AASHTO LRFD Specifications overestimate the longitudinal bending moment and shear force. This overestimation increases with increase of skew angle and reaches 12% for skew angle of 20° and 45% for 45°. The results show that transverse diaphragms perpendicular to the longitudinal girders of the bridges are the best arrangement for load distribution. Comparing results of simplified relations for skewed decks with finite‐element analysis show that the results of proposed equations are conservative for continuous‐skewed bridges. It must be mentioned that the results are for those bridges with specific configuration and the results may change if the presumed conditions vary; although the tendency should be similar.

Select this Article		Regularity Criteria for RC and PRC Multi‐Span Continuous Bridges M. Grendene, P. Franchetti, and C. Modena Journal of Bridge Engineering doi:http://dx.doi.org/10.1061/(ASCE)BE.1943-5592.0000267 Posted ahead of print 5 May 2011 Full Text: \| Download PDF
	+ -	Show Abstract A parametric study was carried out in order to provide criteria for structural regularity on reinforced concrete (RC) or precast reinforced concrete (PRC) multi‐span continuous bridges, assessing whether an equivalent single degree of freedom (ESDOF) system represents a multi degree of freedom (MDOF) system correctly. The ESDOF system, determined by means of a non linear static analysis (NLSA), is compared, in terms of displacements, with the original MDOF through a non‐linear dynamic analysis. To this end, a sample of 32 bridges was considered in order to take into account the effect of stiffness ratio between different piers and between piers and deck. Together with the evaluation of the reliability of the regularity indexes found in literature, a comparative analysis was carried out. The results showed that the simplified system is representative of the bridge global behavior either when the deck is enough stiff to control pier displacements and deformations, or when pier distribution is symmetric.