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Select this Article		Behaviour of Full‐Scale Railway Turnout Sleepers from Glue‐Laminated Fibre Composite Sandwich Structures Allan Manalo and Thiru Aravinthan Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000307 Posted ahead of print 30 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract An experimental study on the flexural and shear behaviour of the full‐scale glue‐laminated composite sandwich beams in three different layouts was conducted to evaluate the suitability of this construction system for railway turnout sleepers. The building block of this innovative beam is a novel composite sandwich structure made up of glass fibre composite skins and modified phenolic core material that has been specifically developed for civil engineering applications. The sandwich beam is produced by gluing layers of fibre composite sandwich structure together in flatwise (horizontal) and in edgewise (vertical) orientations. The glued sandwich beams with edgewise laminations presented appropriate strength and stiffness for replacement turnout timber sleeper. The mechanical properties of these glue‐laminated sandwich beams are comparable with the existing timber turnout sleepers demonstrating that the innovative composite sandwich beam is a viable alternative sleeper material for railway turnouts. From this study, it is concluded that the glue‐laminated composite sandwich structures have the potential to be used for replacement railway turnout sleepers. An enhanced understanding of the behaviour of fibre composite sandwich structures for potential civil engineering applications is also an outcome of this investigation.

Select this Article		Case Study on Evaluating the Long‐Term Durability of Externally‐Bonded FRP via Field Assessments Douglas G. Allen and Rebecca A. Atadero Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000305 Posted ahead of print 30 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract Fiber Reinforced Polymer Composites (FRP) are an attractive repair option for reinforced concrete structures, but while laboratory durability tests have indicated that FRP generally performs well in many environments their long term performance in field environments is not well understood. This case study describes an effort to collect in‐situ data about the FRP used to repair a concrete arch bridge eight years after the FRP was originally placed. On site assessment efforts included inspection for voids between the concrete and FRP using acoustic sounding and thermographic imaging, and pull‐off tests to check the bond strength. Large debonded regions of FRP were also cut from the structure and tested in tension in the laboratory. Results generally pointed to some level deterioration: many new voids were found and existing voids had grown, pull‐off testing showed weaker bond strengths, and the tensile strengths were quite low compared to design values. However, a lack of initial data makes it difficult to distinguish between deterioration over time, and the possibility of lower strengths due to field manufacture techniques.

Select this Article		Effect of Adhesive Thickness and Concrete Strength on FRP‐Concrete Bonds Julio C. López‐González, Jaime Fernández‐Gómez, and Enrique González‐Valle Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000303 Posted ahead of print 26 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract The use of composite materials for strengthening, repairing or rehabilitating concrete structures has become more and more popular in the last ten years. Irrespective of the type of strengthening used, design is conditioned, among others, by concrete‐composite bond failure, normally attributed to stress at the interface between these two materials. Single shear, double shear and notched beam tests are the bond tests most commonly used by the scientific community to estimate bond strength, effective length and the bond stress‐slip relationship. The present paper discusses the effect of concrete strength and adhesive thickness on the results of beam tests, which reproduce debonding conditions around bending cracks much more accurately. The bond stress‐slip relationship was analyzed in a cross‐section near the inner edge, where stress was observed to concentrate. The ultimate load and the bond stress‐slip relationship were visibly affected by concrete strength. Adhesive thickness, in turn, was found to have no significant impact on low‐strength concrete but a somewhat greater effect on higher strength materials.

Select this Article		Axial and Flexural Performance of Square RC Columns Wrapped with CFRP under Eccentric Loading Muhammad N. S. Hadi, M. ASCE and Ida Bagus Rai Widiarsa Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000301 Posted ahead of print 26 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract The majority of studies on FRP strengthened concrete columns deal with columns of a circular cross section. However, most concrete columns in the field have square or rectangular cross sections and resist eccentric loads as well. This paper presents the results of the experimental study on the performance of CFRP wrapped square RC columns under eccentric loading. The influence of the number of CFRP layers, the magnitude of eccentricity and the presence of vertical CFRP straps were investigated by testing sixteen specimens. The specimens had the dimensions of 200 mm × 200 mm × 800 mm and round corners with a radius of 34 mm. Twelve specimens were tested as columns and four specimens were tested as beams. Results of this study showed that CFRP wrapping enhanced the load‐carrying capacity and ductility of the columns under eccentric loading. Furthermore, the application of the vertical CFRP straps improved significantly the performance of the columns with large eccentricity.

Select this Article		Retrofitting of Severely Shear‐Damaged Concrete T‐Beams Using Externally Bonded Composites and Mechanical End Anchorage Tamer El‐Maaddawy and Yousef Chekfeh Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000299 Posted ahead of print 10 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract The effectiveness of using externally‐bonded carbon fiber reinforced polymer (EB‐CFRP) system with mechanical end anchorage to retrofit severely shear‐damaged reinforced concrete (RC) beams is examined in this paper. A total of 14 tests were performed on eight RC beams with a T‐shaped section and low compressive strength. To represent a severe shear‐damage condition, five beams were tested to failure, retrofitted, then retested to failure for a second time. Test parameters included the number of EB‐CFRP layers and type of end anchorage system. The results demonstrated that retrofitting of severely shear‐damaged RC T‐beams with EB‐CFRP composites and proper mechanical end anchorage can fully restore the original shear capacity of the beams. The use of a sandwich composite panel in combination with a threaded anchor rod inserted through the entire web width (thru‐bolt) as an end anchorage system was more effective than using the panel with side powder‐actuated fasteners. Increasing the number of EB‐CFRP layers did not result in additional gain in shear capacity. The accuracy and validity of four different international guidelines/standards were examined by comparing their predictions with the experimental results.

Select this Article		Experimental Investigation of Bond Fatigue Behaviour of Concrete Beams Strengthened with NSM Prestressed CFRP Rods Noran Wahab, Khaled A. Soudki, and Timothy Topper Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000298 Posted ahead of print 10 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract Bond tests were conducted on ten concrete beams strengthened with near‐surface mounted (NSM) prestressed carbon fibre reinforced polymer (CFRP) rods under different fatigue load levels. In the NSM technique, grooves are cut on the tension side of the beams. The CFRP rods are then placed inside the grooves and prestressed. Then the epoxy adhesive is placed inside the groove to provide bond between the concrete and the CFRP rod. The test variables included: the type of the CFRP rod (spirally wound, sand coated) and the fatigue load level. The beams were tested in four‐point bending. Unlike the bond failures for beams strengthened with non prestressed CFRP rods, bond failure for the beams strengthened with prestressed CFRP rods and tested under fatigue loading was by slipping between the CFRP rod and the epoxy that started at the support and propagated inwards towards the loading point. The sand coated rods showed a better bond fatigue performance than the spirally wound rods where at a given load level the beams strengthened with sand coated rods had a longer fatigue lives than the beams strengthened with spirally wound rods. Also, for a given number of cycles, the beam strengthened with prestressed CFRP rods failed in bond at a lower applied load range than the beam strengthened with non‐prestressed CFRP rod. At onset of excessive slip (failure), the force distribution in the CFRP rod in the end region is the same for a given rod type. Thus, the shear stress value and distribution in the region close to the support is the same at onset of excessive slip (failure) for a given rod type regardless of the applied load level.

Select this Article		Numerical Investigation on the Influence of FRP Retrofit Layout and Geometry on the In‐Plane Behavior of Masonry Walls Gian Piero Lignola, Andrea Prota, and Gaetano Manfredi Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000297 Posted ahead of print 10 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract Un‐Reinforced masonry (URM) structures have shown their vulnerability to major events like as earthquakes, severe wind, blast and impact. The present work started from experimental programs, available in scientific literature, related to masonry walls made of clay or natural stone units. The Finite Element Method (FEM) was used in order to describe the global behavior of tested specimens, in terms of shear/displacement curves, shear capacity and cracking pattern. FEM, and particularly detailed micro‐modeling, was adopted as a numerical simulation tool for masonry walls. International Design Codes underline that some Fiber Reinforced Polymers (FRP) dimensions (e.g. width, thickness and spacing of FRP strips applied as external strengthening of URM walls made of different brickworks) may influence the global behavior of strengthened masonry. The present work, starting from experimental programs, by other research groups, related to walls made of solid and hollow clay units as well as natural tuff units, subjected to compression/shear loading, aims at identifying the actual influence of those dimensions. Diagonal and horizontal strips were investigated. Different brickwork panels having the same FRP strengthening (quantity and geometry) showed different behaviors. Present outcomes highlighted that the influence of some FRP strengthening parameters (e.g. strip spacing) is not so meaningful, if compared to FRP total amount, even if the code formulations predict significant differences.

Select this Article		Effect of Temperature Variation on the Full‐Range Behavior of FRP‐to‐Concrete Bonded Joints W. Y. Gao, J. G. Teng, and Jian‐Guo Dai Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000296 Posted ahead of print 10 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract Service temperature variations (thermal loadings) may significantly affect the behavior of the bond between externally bonded fiber reinforced polymer (FRP) and concrete. This paper presents an analytical solution for the full‐range deformation process of FRP‐to‐concrete bonded joints under combined thermal and mechanical loadings. The solution is based on a bilinear bond‐slip model and leads to closed‐form expressions. The validity of the solution is demonstrated through comparisons with both experimental results and finite element predictions. Numerical results from the solution are presented to illustrate the effect of thermal loading on the interfacial shear stress and slip distributions as well as the global load‐displacement response. It is shown that, provided the material properties are not affected by temperature variations, a temperature rise increases the ultimate load while a temperature reduction decreases the ultimate load; the latter can have serious implications for the safety of the strengthened structure. While the solution is developed with particular reference to FRP‐to‐concrete bonded joints, it is also applicable to similar bonded joints made of other materials (e.g. FRP‐to‐steel bonded joints). A useful function of the closed‐form solution lies in the interpretation of pull test results: the solution allows the effect of thermal stresses to be isolated from the effect of property changes of the bondline in obtaining bond‐slip responses from pull tests.

Select this Article		Design ‐ Oriented Strength Model for FRP Confined Concrete Members Theodoros C. Rousakis, Theodoros D. Rakitzis, and Athanasios I. Karabinis Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000295 Posted ahead of print 10 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract The study concerns assessing 20 existing models for predicting the compressive strength of concrete uniformly confined externally with composite materials. An extended database of 471 experiments on cylindrical concrete columns is utilized for the comparisons. The research classifies the experimental data in three distinguished subcategories according to the information available for the mechanical properties of the FRPs in order to investigate their effect on the divergences of the models. Apart from the use of the tensile strength obtained from coupon tests, the use of properties from the manufacturer data on FRP fibers can lead to minimum error of predicted strength of concrete externally wrapped or encased in FRP tubes. The study results in the proposal of an upgraded empirical model that encompasses indirectly the unique deformational characteristics of different Young's moduli of FRP sheets and tubes. The model utilizes the strong linear dependence of the product of the varying effective strain at failure of the confining material (ϵ_je) times the varying confinement effectiveness coefficient (k₁) on the Young's modulus of the reinforcing fibers (E_f). Thus, there is no need to estimate average empirical constant values for the ϵ_je or k₁ and a more rational approach comes up that further restricts errors in strength modeling. The proposed model provides a prediction with absolute average error of 8.6% for wrapped columns and of 6.3% for FRP tube encased columns.

Select this Article		Impact Behaviors of CFT and CFRP Confined CFT Stub Columns Yan Xiao and Yali Shen Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000294 Posted ahead of print 10 April 2012 Full Text: \| Download PDF
	+ -	Show Abstract Concrete‐filled steel tube (CFT) structures are widely used in various types of buildings and bridges. Confined concrete tube (CCFT) is a new type of structural column originally proposed by the first writer. This paper reports the impact testing results of the CFT and carbon fiber reinforced polymer (CFRP) confined CFT stub columns under different impacting energy levels, conducted using a large‐capacity drop‐hammer machine. The time history curves of impacting force and deformation time history curves as well as failure patterns are investigated. The results indicate that the failure patterns are related to the impact energy. Increasing the thickness of steel tube and providing additional transverse confinement by CFRP can enhance the impact‐resistant behavior. Finally, the dynamic analysis software ANSYS/LS‐DYNA are used to simulate the impact behaviors of the CFT and CCFT specimens, and the simulation results are reasonable comparing with the test results.

Select this Article		Slenderness Limit for Short FRP‐Confined Circular RC Columns T. Jiang and J. G. Teng Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000293 Posted ahead of print 20 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract Strengthening of RC columns through lateral confinement provided by external fiber‐reinforced polymer (FRP) jackets (or wraps) has become an increasingly popular technique over the past decade. Nevertheless, relevant design provisions in existing design guidelines are only concerned with the design of FRP jackets for short columns in which the slenderness effect is negligible. Even for the safe application of the existing design provisions for short columns, there is an urgent need to define a slenderness limit for short FRP‐confined columns. This paper proposes such a slenderness limit expression based on the numerical results of a comprehensive parametric study which investigates the effects of various parameters on the slenderness limit using a recently developed theoretical column model. An important feature of the proposed expression is that it separates the effect of FRP confinement on the slenderness limit from the effect of other parameters. This feature allows existing slenderness limit expressions for short RC columns of different forms to be readily upgraded for use in the design of FRP‐confined RC columns by incorporating the part dealing with the effect of FRP confinement in the proposed expression.

Select this Article		Experimental Tests and Design Model for RC Beams Strengthened in Shear Using the Embedded Through‐Section FRP Method Amir Mofidi, Omar Chaallal, Brahim Benmokrane, and Kenneth Neale Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000292 Posted ahead of print 5 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract This paper presents results of an analytical and experimental investigation on reinforced concrete (RC) T‐beams retrofitted in shear with embedded through‐section (ETS) fiber‐reinforced polymer (FRP). The ETS FRP rod method is a promising method to increase the shear strength of RC beams. As this method develops, the structural behavior of RC beams strengthened with the ETS method needs to be thoroughly characterized and the influencing parameters addressed. In this research study, nine tests were performed on 4520‐mm‐long RC T‐beams. The parameters of this study are: (i) the effect of the surface coating on the FRP bars; (ii) the effect of internal transverse‐steel reinforcement on the FRP shear contribution; (iii) the effect of FRP bar spacing; (iv) the effect of FRP rod diameter; and (v) the efficiency of the embedded through‐section FRP rod method. The main objective of the study is to analyze the behavior of RC T‐beams strengthened in shear with ETS FRP rods by varying the parameters just mentioned. New design equations are proposed to calculate the shear contribution of FRP for beams strengthened using the ETS FRP method. The design equations are validated against results collected from the experimental part of the current research study. The proposed model shows an acceptable correlation with the experimental results.

Select this Article		Environment‐Assisted Subcritical Debonding of Epoxy‐Concrete Interface Chao Zhang, A. M. ASCE, Jialai Wang, M. ASCE, and Kenneth J. Fridley, F. ASCE Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000291 Posted ahead of print 5 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract Interface debonding can grow slowly within the FRP‐to‐concrete interface in aggressive environments, even though the energy release rate at the crack tip is only a fraction of the critical energy release rate of the interface. This slow debonding process is called environment‐assisted subcritical debonding, which may be a dominant mechanism for the failure of the FRP‐to‐concrete interface under service loads in aggressive environments. In this study, environment‐assisted subcritical debonding of the epoxy‐concrete interface was first observed and characterized using wedge‐driven testing. It has been found that aggressive environments can substantially increase the debonding growth rate along the epoxy‐concrete interface. Fracture surface analysis suggests that the debonding mode can change from the cohesive failure within the concrete in critical debonding to the adhesive failure along the epoxy‐concrete interface in subcritical debonding. The proposed subcritical debonding testing closely simulates the failure occurring during the service‐life of the FRP‐to‐concrete interface, and allows interaction with environmental species during testing. Subcritical debonding testing provides a new approach to understand the degradation mechanism and to assess the long‐term durability of the FRP‐to‐concrete interface.

Select this Article		Repair and Strengthening of Reinforced Concrete Beam‐Column Joints with Fiber Reinforced Polymer Composites Halil Sezen Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000290 Posted ahead of print 8 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract Three exterior reinforced concrete beam‐column joint specimens were tested under reverse cyclic loading. The joint region of these specimens suffered significant damage while limited damage was observed in the beams. The damaged specimens were repaired and strengthened to prevent shear damage and strength deterioration inside the joint region and to achieve more ductile response. First, the damaged loose concrete was removed and replaced by high strength non‐shrink mortar. Then, fiber reinforced polymer (FRP) strips were diagonally wrapped over the joint region and longitudinal FRP strips were applied and anchored on the beams. The original strength was restored in all strengthened specimens under the application of the same loading history. Deformation capacities of the strengthened specimens were much larger than those of the original specimens.

Select this Article		Flexural Performance and Moment Connection of Concrete‐Filled GFRP Tube‐Encased Steel I‐Sections Sarah Zakaib and Amir Fam, M. ASCE Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000288 Posted ahead of print 3 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract A hybrid system, namely concrete‐filled FRP tube (CFFT)‐encased steel I‐section, is introduced. The embedded steel section enhances flexural strength and stiffness, and provides a pseudo‐ductile behavior. It also facilitates connection of the CFFT member to footings or other members. Phase I of the experimental program addresses the flexural behaviour of the system through ten beam specimens, including steel and CFFT control specimens. The GFRP tubes varied in thickness and laminate structure. The steel section enhanced performance considerably, especially pseudo‐ductility, in tubes with cross‐ply laminates, where a significant sustained reserved strength remains stable over large deflections upon fracture of the tube. CFFTs with angle‐ply tubes showed a considerable inherent ductility on their own, in which case, adding the steel section enhanced strength and stiffness only. Phase II addresses a moment connection through five cantilever tests. The connections consist of steel base plates welded to the steel sections, which are embedded into the CFFT members at various lengths (L_s)‐to‐span length (L) ratios of 0.1 to 1.0. Three distinct failure modes are observed. At (L_s/L) ratios up to 0.17, premature bond failure occurs. At ratios of 0.17 to 0.47, the CFFT member achieves flexural tension failure of the tube just beyond the free end of the steel section. Beyond a 0.47 ratio, the full plastic hinge capacity is developed at the fixed end. A simple design‐oriented model that predicts strengths at the full range of (L_s/L) ratios is developed and validated.

Select this Article		Effects of Eccentricity on the Seismic Rehabilitation Performance of Nonseismically Detailed Interior Beam‐Wide Column Joints Bing Li, Qian Kai, and Weichen Xue Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000287 Posted ahead of print 3 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract In this paper, the effects of the eccentricity on the effectiveness of fiber‐reinforced polymers (CFRP) or glass fiber reinforced polymer (GFRP) in repairing the shear strength and ductility of nonseismically detailed beam‐wide column joints have been evaluated. For this purpose, four (two concentric and two eccentric) full‐scale nonseismically detailed interior beam‐wide column joints were used as control specimens. All four subassemblages were subjected to similar cyclic lateral displacement so as to provide the equivalent of severe earthquake damage. The damaged control specimens were then repaired by filling their cracks with epoxy and externally bonding them with CFRP sheets and GFRP sheets. These repaired specimens were then re‐tested and their response histories were obtained. Hence, a total of eight specimens were tested: four control, and four repaired. The response histories of the control and repaired specimens were then compared. The results were compared through hysteretic loops, load‐displacement envelopes, energy dissipation capacity, secant stiffness degradation, and shear strength and damage indices. Moreover, the effectiveness of the proposed repair schemes in repairing the eccentric and concentric joints was also compared. The present study demonstrates that proposed repair schemes can recover the performance of both damaged RC concentric and eccentric beam‐wide column joints effectively.

Select this Article		FE Modeling of CFRP‐Repaired RC Beams Subjected to Fatigue Loading Kam Yoke M. Loo, Stephen J. Foster, and Scott T. Smith, M. ASCE Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000286 Posted ahead of print 3 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract A constitutive model is developed for fibre‐reinforced polymer (FRP)‐to‐concrete bond for fatigue loading. The model is verified against available test data with a framework developed for further calibration as new data becomes available. The formulation is incorporated in to a finite element program and the fatigue behavior of FRP‐repaired reinforced concrete (RC) beams analyzed. In comparing the finite element model results with test data it is shown that the model is capable of accurately predicting the overall cyclic fatigue loading response of RC members strengthened with FRP composites. The model is also able to capture the change in the peak deflection, the FRP plate strain development and distribution with increasing number of load cycles, as well as the number of load cycles to failure. The need for more tests on FRP‐to‐concrete bonded interfaces subjected to fatigue loading is identified as well as the need to measure key modeling parameters from such tests.

Select this Article		Rapid Strengthening of Masonry Structures Cracked in Earthquakes Using Fiber Composite Materials Xianglin Gu, Bin Peng, Gonglian Chen, Xiang Li, and Yu Ouyang Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000285 Posted ahead of print 3 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract Many masonry structures have cracking problems after earthquake exposure. Rapid and reliable rehabilitation of such masonry structures is necessary for disaster relief purposes. To improve current strengthening methods for masonry structures with cracking problems by use of fiber reinforced polymer, investigation on strengthening of a scaled five‐story masonry structure built with concrete perforated bricks was conducted. The structure was initially tested on a shake table, from which its displacement, acceleration responses and cracking were recorded. Rapid strengthening (in less than three days) was performed for the partially damaged structure by use of basaltic fiber reinforced polymer (BFRP) for its low elastic modulus and high strength (good compatibility with masonry substrate). The strengthening was carefully designed and special anchorage measures were used on the first floor of the structure to ensure the strengthening effect of the externally bonded BFRP stripped sheets. The strengthened structure was then retested on the shake table to quantify the strengthening effect. By comparing the performance of the masonry structure during the two shake table tests, it was found that the externally bonded BFRP sheets worked well with the masonry structure and the seismic performance of the masonry structure was improved significantly.

Select this Article		Effective Moment of Inertia Prediction of FRP Reinforced Concrete Beams Based on Experimental Results S. Roohollah. Mousavi and M. Reza. Esfahani Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000284 Posted ahead of print 3 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract Concrete beams reinforced with glass fiber reinforced polymer (GFRP) bars exhibit large deflections in comparison with steel reinforced concrete beams due to the low modulus of elasticity of GFRP bars. This paper proposes new equations for estimating the effective moment of inertia of FRP reinforced concrete beams based on the genetic algorithm and experimental results. Genetic algorithm is used to optimize the error function between experimental and analytical responses. In the experimental part of the study, nine beam specimens were manufactured and tested. In addition, the results of fifty five beam specimens tested by other researchers are also used in this study. The effects of elastic modulus of FRP bars, reinforcement ratio and the level of loading on the effective moment of inertia are taken into account. The proposed equations are compared with different code provisions and previous models for predicting the deflection of FRP reinforced concrete beams. The values calculated by the proposed equations are also compared with different test results. The experimental results correlated well with the values predicted by the proposed equations, especially in the cases of high reinforcement ratios and high levels of loading.

Select this Article		Normalized Confinement Stiffness Approach for Modeling FRP Confined Concrete Veysel Yazici and Muhammad N. S. Hadi Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000283 Posted ahead of print 3 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract Passive confinement provided by fiber reinforced polymer (FRP) jackets has been proven to increase the compressive strength and axial deformation capacity of concrete by many researchers. This study explains a normalized confinement stiffness approach to quantify the strength and strain increase of FRP confined concrete using a previously proposed and most widely used model for both active and passive confinement of concrete and claims that these equations can still be used for FRP confined concrete with very simple modifications. A comparison of the accuracy of the proposed model to ACI440‐2R‐02 and ACI440‐2R‐08 guidelines was made using the experimental results reported in the literature by different researchers. The proposed modified model was shown to be quite effective in predicting the increased strength and strain values of FRP confined concrete. The proposed model was also modified for FRP confined hollow concrete cylinders.

Select this Article		FRP/Masonry Debonding: A Numerical and Experimental Study of the Role of Mortar Joints Christian Carloni and Kolluru V. Subramanian Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000282 Posted ahead of print 3 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract FRP composites are used as supplementary reinforcement to increase the in‐plane shear capacity or to provide out‐of‐plane load‐carrying capability of masonry walls and to modify the collapse mechanism in arches and vaults. In these applications, the efficiency of load transfer is limited by the debonding of FRP from the masonry substrate. In this paper, the debonding mechanism of FRP/masonry is experimentally studied. Experimental procedure and test specimens are designed to investigate the progressive debonding of FRP from brick and mortar substrates and relate it to the response obtained from the FRP/masonry interface. Surface displacements during debonding are obtained using digital image correlation. A one‐dimensional numerical model is developed for predicting the fracture behavior along the FRP/masonry interface using the cohesive fracture parameters from the brick and mortar interfaces, obtained from the computed strains.

Select this Article		Performance under Fire Situations of Concrete Members Reinforced with FRP Rods: Bond Models and Design Nomograms Emidio Nigro, Antonio Bilotta, Giuseppe Cefarelli, Gaetano Manfredi, and Edoardo Cosenza Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000279 Posted ahead of print 23 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract Intuitively, the fire endurance of concrete members reinforced with Fiber Reinforced Polymer (FRP) bars is related to the decrease in the mechanical properties of the materials concerned, especially resin. Large‐scale fire tests recently performed on nine concrete slabs reinforced with glass FRP bars demonstrated the importance of bond between FRP and concrete for performance under fire situations. Our experimental results showed that (a) the length of the FRP bars in the zone of slabs not directly exposed to fire (namely anchoring length in fire situations) can be much more relevant to fire endurance than the concrete cover in the zone directly exposed to fire, and (b) the shape of the bar, for instance bent at the end, allows a reduction in anchoring length. From a design point of view, evaluating the necessary anchoring length through a bond model seems a key aspect. Full scale test results, extensively presented elsewhere, are used in this paper to investigate the bond behavior of FRP bars embedded in concrete at high temperature and assess a procedure to predict bond stress, slip, and load transfer at elevated temperature, based on both the results of numerical thermal analysis and the predictions of a bond theoretical model adjusted for fire situations. The design procedure outlined for calculating the minimal required anchoring length proves a valuable approach for the practicing engineer and stands together with the experimental and numerical results presented earlier. Finally, design nomograms are shown as examples of application of the procedure.

Select this Article		Behavior of Large‐Scale Concrete Columns Wrapped with CFRP and SFRP Sheets Khaled Abdelrahman and Raafat El‐Hacha Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000278 Posted ahead of print 23 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract Circumferential wrapping of Fiber Reinforced Polymer (FRP) sheets is one of the most common applications for repair and rehabilitation of large‐scale columns. Common types of fibers used for wrapping are Carbon FRP (CFRP), Glass FRP (GFRP) and Aramid FRP (AFRP). Recently, Steel FRP (SFRP) has been introduced as a new class of composites for strengthening applications. Up to date, there is no experimental data available on the behavior of large‐scale columns wrapped with SFRP sheets. Thus, in this paper, the behavior of non‐reinforced and reinforced large‐scale columns (300×1200mm) wrapped with CFRP and SFRP sheets is examined and compared with unwrapped columns. The experimental results include stress‐strain behavior, ultimate stress, ultimate strain, dilation and ductility of large‐scale columns. This study presents first ever insight of the strain variation of large‐scale circular columns wrapped with CFRP and SFRP sheets using Digital Image Correlation Technique (DICT). DICT is a photogrammetric technique that allows capturing strains from the surface of FRP confined concrete. Results from DICT were used to analyze the strain efficiency of the SFRP sheets. Results indicate that the overall performance of the SFRP wrapped concrete columns is superior to the CFRP wrapped concrete columns.

Select this Article		Modeling of Buckling and Wrinkling Behavior in GFRP Plate and Sandwiches subjected to Biaxial Compression—Tension Loading Behzad D. Manshadi, Anastasios P. Vassilopoulos, Julia de Castro, and Thomas Keller Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000277 Posted ahead of print 20 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract A model for predicting the buckling and wrinkling behavior of composite plates and sandwich panels subjected to in‐plane biaxial compression‐tension loading is presented in this paper. In‐plane biaxial compression‐tension loading occurs in the webs of plate girders or cell‐core sandwiches. The model is able to simulate two counteracting effects of increasing transverse tension load on buckling and wrinkling loads as observed in experiments. A stabilizing effect tends to push the plate back to the median plane and thereby delays the onset of buckling/wrinkling instability. In contrast, lateral contraction accelerates the bending of the plate which leads to a significant decrease in buckling/wrinkling loads. In composite plates, the first effect predominates and increases the buckling loads while in sandwich panels the second effect is dominant and decreases the wrinkling loads. The theoretical predictions are in good agreement with the corresponding experimental results.

Select this Article		Anchorage Devices used to improve the Performance of Reinforced Concrete Beams Retrofitted with FRP Composites: A‐State‐of‐the‐Art‐Review R Kalfat, R Al‐Mahaidi, and Scott T. Smith, M. ASCE Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000276 Posted ahead of print 20 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract The anchorage of fibre‐reinforced polymer (FRP) composites when applied to reinforced concrete (RC) structures as externally bonded reinforcement is an effective means to achieve higher levels of fibre utilisation prior to premature debonding failure. Commonly documented anchorage methods for FRP‐to‐concrete applications with encouraging results include: FRP U‐jackets, FRP anchors (also known as spike anchors amongst other names), patch anchors (utilising unidirectional and bidirectional fabrics), nailed metal plates (also known as hybrid bonding), near‐surface mounted rods, mechanical fastening, concrete embedment and mechanical substrate strengthening. Anchorages applied to FRP systems have been verified through experimental testing and numerical modelling to increase the ductility, deformability and strength of the member and also prevent, delay or shift the critical mode of FRP debonding failure. Although the benefits of anchorage solutions have now been widely acknowledged by researchers, further studies are required in order to establish reliable design formulations to negate the requirement for ongoing laboratory verification by industry. The present paper is a state‐of‐the‐art‐review of experimental studies conducted in the area of FRP anchorage systems applied to FRP‐strengthened RC flexural members. Available experimental data are compiled and catalogued and an anchorage efficiency factor for each anchorage type under investigation is assigned in order to quantify the anchor's efficiency. Finally, current shortcomings in knowledge are identified in addition to areas needing further investigation.

Select this Article		Time‐Variant Reliability Analysis and Flexural Design of GFRP‐Reinforced Bridge Young Hoon Kim, David Trejo, and Paolo Gardoni Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000275 Posted ahead of print 20 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract Glass-fiber reinforced polymer (GFRP) reinforcement is being used in bridge decks as a replacement for steel reinforcement. It is thought that since the GFRP reinforcement does not corrode, it can be a more sustainable material for reinforced concrete structures. However, it is widely reported that GFRP bars do deteriorate when embedded in concrete or when immersed in concrete pore solutions. The American Concrete Institute (ACI) and the American Association of State Highway Transportation Officials (AASHTO) use environmental exposure factors to reduce the design strength due to this loss of capacity. However, these exposure factors have not been calibrated. In addition, limited research has been performed to quantify the time-variant flexural moment capacity of GFRP reinforced flexural members. Recently, a Bayesian approach was used to develop a time-variant probabilistic capacity model based on capacity data of GFRP reinforcement embedded in concrete for a period of up to 7 years. This model is used herein to assess the time-variant flexural moment capacity and the time-variant structural reliability of a bridge deck considering different types and sizes of GFRP bars. Even though GFRP reinforced bridge decks are designed to be over-reinforced and the designs are governed by the serviceability limit, the analysis results indicate that the probability of failure of the decks containing both 13M (#4) and 19M (#6) GFRP bars at a reference temperature T₂₃ of 23 °C (73 °F) is higher than the failure probability generally accepted in the AASHTO Load and Resistance Factor Rating (LRFR) Specifications. A lower exposure temperature reduces the probability of failure over the 75 year period. The probability of failure is less than values accepted by AASHTO.

Select this Article		Behavior of Wide Shallow RC Beams Strengthened with CFRP Reinforcement Abdulaziz I. Al‐Negheimish, Ahmed K. El‐Sayed, Rajeh A. Al‐Zaid, Ahmed B. Shuraim, and Abdulrahman M. Alhozaimy Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000274 Posted ahead of print 20 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract One‐way reinforced concrete joist floor with wide shallow beams (WSBs) are used widely in building construction throughout the Middle East. The short and long term behavior of WSBs externally strengthened with carbon fiber‐reinforced polymer (CFRP) reinforcement was studied on isolated beams and as part of full‐scale building. This paper presents the results of the experimental investigation on the flexural performance of isolated WSBs externally strengthened with CFRP reinforcement. A total of six full‐scale beams were constructed and tested to failure. The test variables were the amount, type, configuration, and the elastic modulus of CFRP reinforcement. The test results were presented in terms of deflections, ultimate capacities and modes of failure, crack width development, and strains in reinforcement and concrete. The test results showed significant improvement in the flexural performance of the strengthened beams with respect to flexural capacity, flexural stiffness and crack width. All but one of the strengthened beams failed due to debonding of CFRP reinforcement; however, the load carrying capacity of WSBs were more than that predicted by ACI 440 ‐08 design method.

Select this Article		Behavior of FRP‐Confined Normal‐ and High‐Strength Concrete under Cyclic Axial Compression Togay Ozbakkaloglu and Emre Akin Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000273 Posted ahead of print 10 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract An important application of fiber reinforced polymer (FRP) composites is as a confining material for concrete, in both the seismic retrofit of existing reinforced concrete columns and in the construction of concrete‐filled FRP tubes as earthquake‐resistant columns in new construction. The reliable design of these structural members against earthquake‐induced forces necessitates a clear understanding of the stress‐strain behavior of FRP‐confined concrete under load cycles. This paper presents the results of an experimental study on the behavior of FRP‐confined normal‐ and high‐strength concrete under axial compression. A total of 24 aramid and carbon FRP‐confined concrete cylinders with different concrete strengths and FRP jacket thicknesses were tested under monotonic and cyclic loading. Examination of the test results have lead to a number of significant conclusions in regards to both the trend and ultimate condition of the axial stress‐strain behavior of FRP‐confined concrete. These results are presented and a discussion is provided on the influence of the main test parameters in the observed behaviors. The results are also compared with two existing cyclic axial stress‐strain models for FRP‐confined concrete.

Select this Article		Instantaneous Load Intensities Incorporated with a Cold Region Environment for CFRP‐Confined Concrete in Axial Compression Mozahid Hossain and Yail J. Kim Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000272 Posted ahead of print 10 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract This paper presents the durability performance of axially‐loaded concrete cylinders with or without carbon fiber reinforced polymer (CFRP) confinement subjected to a typical cold region environment associated with various instantaneous load intensities. In fact, these factors have been identified from previous research that examines critical attributes affecting the deterioration of constructed bridges in cold climate: aging and live load. A total of 31 cylinders are tested to study the effect of such critical factors. A three‐dimensional finite element model is developed to predict test results. The load‐carrying capacity of the unconfined concrete decreases due to the environmental exposure and the decrease rate is accelerated with the presence of live load effects, including substantial crack propagation. For the confined cylinders, the effect of environment and instantaneous intensities is not significant in terms of strength and energy dissipation. The ACI440.2R‐08 provisions are found to be adequate to estimate the capacity of CFRP‐confined concrete subjected to a combined cold region environment and live load effect.

Select this Article		Fire Behavior of Thin CFRP Pretensioned High Strength Concrete Slabs Giovanni Pietro Terrasi, Luke Bisby, Michel Barbezat, Christian Affolter, and Erich Hugi Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000271 Posted ahead of print 10 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract More sustainable precast concrete structural elements are emerging from the research community utilizing high‐strength, self‐consolidating, fiber reinforced concrete (HPSCC) reinforced with non‐corroding prestressed carbon fiber reinforced polymer (FRP) reinforcement. An example of this is a new type of precast carbon FRP pretensioned HPSCC panel intended as load‐bearing beams and/or columns for use in building envelopes. Such elements have recently been applied for architectural façade elements in Europe. A key issue in the implementation of these elements as load carrying members in buildings is demonstrating satisfactory performance in fire. It is well known that the bond between FRP reinforcing bars and concrete deteriorates at elevated temperature. It is also known that high strength concrete is susceptible to explosive spalling when subjected to fire. Reductions in FRP reinforcement tensile and bond strength during fire, impacts on the load‐bearing capacity of prestressed concrete structures, and the explosive spalling response of HPSCC during fire all remain largely unknown. This paper provides insights into the fire behavior of CFRP prestressed HPSCC slabs through an experimental study on thin slabs exposed to a standard fire while subjected to sustained service loads. It is shown that the fire resistance of these elements is governed by fire‐induced spalling or, if spalling is prevented by the use of high dosages of polypropylene microfibers in the concrete, by thermal splitting‐crack induced bond failure of the CFRP tendons in their prestress transfer zone. Neither reductions in tensile strength of the tendons nor reductions in bond strength due to resin softening at high temperature appeared to play critical roles for the tests described herein. Key areas for future research are highlighted.

Select this Article		Bond Durability of FRP Bars Embedded in Fiber‐Reinforced‐Concrete Abdeldjelil Belarbi, F. ASCE, P.E. and Huanzi Wang, M. ASCE, P.E. Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000270 Posted ahead of print 10 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract A research program was initiated to develop a nonferrous reinforcement system for concrete bridge decks using continuous FRP bars and discrete, randomly distributed polypropylene fibers. This hybrid system may eliminate problems related to corrosion of steel reinforcement while providing requisite strength, stiffness, and desired ductility, which are shortcomings of the FRP reinforcing system in plain concrete. This paper presents the results of a part of this research program, i.e., the long‐term bond behaviors of this FRP/FRC hybrid system. Bond durability for the FRP/plain concrete system that served as a reference is also reported. Test results indicated that ultimate and design bond strength experienced noticeable degradation when exposed to combined environmental conditioning, including freeze‐thaw cycles, high temperature (60°C), and de‐icing salt solution. Test results showed that bond durability significantly improved due to the restriction of the concrete crack by the addition of polypropylene fibers. The larger specimens with thicker concrete cover and relatively smaller direct exposed area to the solution of sodium chloride (NaCl) showed better bond durability. Comparing GFRP specimens with CFRP specimens, it was found that bond degradation was tightly correlated to the degradation of FRP bar.

Select this Article		Influences of Material Properties on Energy Absorption of Composite Sandwich Panels under Blast Loads Hong Su, S. M. ASCE and Jennifer McConnell, A. M. ASCE Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000269 Posted ahead of print 19 November 2011 Full Text: \| Download PDF
	+ -	Show Abstract This paper presents a study on the influence of material properties on the energy absorption capabilities of composite sandwich panels. This is of interest as increased energy absorption capability is an effective approach to providing blast resistance. The primary scope of work includes finite element parametric studies, carried out using LS‐Dyna, of single fiber reinforced polymer (FRP) composite face sheets and FRP composite sandwich panels, to determine the most influential material property parameters and suggest optimum values for these parameters in conceptual terms. The analyses also consider simultaneously varying the material properties throughout the panel and the influence of independently varying these properties among the different structural components of the panel. The results of this work can serve to design new or specify existing composite materials that have material properties optimized for increasing the blast resistance of composite sandwich panels in future work. Validation of the modeling techniques utilized and the development of quantified energy absorption metrics specific to blast applications are also discussed.

Select this Article		Flexural Behavior of CFRP Precast Prestressed Decked Bulb T Beams Nabil Grace, Tsuyoshi Enomoto, Prince Baah, and Mena Bebawy Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000266 Posted ahead of print 3 November 2011 Full Text: \| Download PDF
	+ -	Show Abstract This study introduces an innovative scheme of bridge superstructure for expedited construction, improved serviceability, and extended lifespan. The new bridge superstructure is assembled from precast prestressed decked bulb T beams reinforced and prestressed with corrosion‐free fiber reinforced polymer (FRP) materials. An experimental investigation accompanied by analytical and numerical simulations was developed to evaluate the performance of the newly developed beams. Through the experimental investigation, three single decked bulb T beams were constructed and tested to failure. The first beam served as a control beam and was prestressed and reinforced with conventional steel strands and reinforcing bars. Second and third beams were prestressed and reinforced with carbon fiber cable composites (CFCC) strands and carbon fiber reinforced polymer (CFRP) tendons, respectively. The investigation revealed that the performance of beams reinforced with CFRP tendons or CFCC strands was comparable with the performance of the control beam at both service and ultimate limit states. All three beams exhibited high load carrying capacity with large corresponding deflection and fair amount of absorbed energy before failure. The study showed that the corrosion‐free FRP‐reinforced decked bulb T beams can be safely deployed in construction to enhance the performance and extend the lifespan of bridge superstructures.

Select this Article		Numerical Investigations on the Seismic Behavior of FRP and TRM Upgraded RC Exterior Beam‐Column Joints Mohammad S. Alhaddad, Nadeem A. Siddiqui, Aref A. Abadel, Saleh H. Alsayed, and Yousef A. Al‐Salloum Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000265 Posted ahead of print 3 November 2011 Full Text: \| Download PDF
	+ -	Show Abstract In this paper a detailed procedure for nonlinear finite element analysis of Fiber Reinforced Polymer (FRP) and Textile Reinforced Mortar (TRM) upgraded RC beam‐column exterior joints is presented for predicting their seismic performance under simulated earthquake loading. The finite element model was developed using a smeared cracking approach for concrete and three dimensional layered elements for the FRP and TRM‐composites. The results obtained from FE analysis were compared with the test results. The tests were conducted on four as‐built exterior beam‐column joint specimens under simulated seismic loads. Out of these four specimens, one specimen was tested as a control specimen and the other three were tested after strengthening with TRM, Carbon FRP and Glass FRP sheets respectively. The FE results were compared with the test results through load‐displacement behavior, ultimate loads, and crack pattern. Comparison of FE results with experimentally observed response indicated that the proposed nonlinear FE model can accurately predict the behavior and response of tested RC beam‐column joints.

Select this Article		Flexural Performance of Steel Girders Retrofitted Using CFRP Materials K. Galal, H. M. Seif ElDin, and L. Tirca Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000264 Posted ahead of print 27 October 2011 Full Text: \| Download PDF
	+ -	Show Abstract There are many existing deteriorated steel bridges that need to be retrofitted. This paper investigates the effectiveness of using carbon fiber‐reinforced (CFRP) composite systems in retrofitting deteriorated steel beams. A total of thirteen medium‐scale steel I‐beams with a span of 1.6m were tested in a four‐point bending setup. The tested beams were divided into four groups according to their studied parameter. Group 1 consists of four un‐retrofitted beams with different percentages of artificial deterioration to simulate corrosion in the bottom flange with the aim to investigate their behavior and to determine the residual flexural capacity. The other three groups have deteriorated steel beams that were retrofitted with different CFRP systems with the aim to evaluate the effectiveness of the proposed retrofit schemes. Four deteriorated beams were retrofitted with CFRP sheets bonded to the tension flange and were tested in Group 2. Group 3 consists of two deteriorated steel beams that were retrofitted with CFRP plates externally bonded to the bottom flange of the tested beams. Group 4 consists of three beams retrofitted using an unbonded CFRP sheets attached to two ductile anchorage systems at the beams' ends. The study shows that steel beams retrofitted with external bonded CFRP systems experienced limited ductility upon the failure of the CFRP either by debonding or rupture at higher load capacities than that of the un‐retrofitted beams. On the other hand, the proposed anchorage system could increase the strength of the deteriorated beam, behave in a ductile manner, and eliminate the early peel off of the CFRP sheet.

Select this Article		Performance of RC Beams Strengthened Using Prestressed NSM‐CFRP Strips Subjected to Fatigue Loading Fadi Oudah and Raafat El‐Hacha Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000262 Posted ahead of print 18 October 2011 Full Text: \| Download PDF
	+ -	Show Abstract The fatigue performance of Reinforced Concrete (RC) beams strengthened using prestressed Near Surface Mounted (NSM) Carbon Fiber Reinforced Polymer (CFRP) strips was evaluated in this paper. Five full‐scale RC beams were tested under fatigue loading simulating in‐service loading conditions; one control un‐strengthened beam and four beams strengthened using NSM‐CFRP strips prestressed to 0, 20, 40, and 60% of the CFRP ultimate tensile strength. All beams were subjected to fatigue loading for 3 million cycles at a frequency of 2.0 Hz such that the stress range induced in the tension steel, in initial cycle, is 125 MPa as specified by the Canadian Highway Bridge Design Code. Experimental test results show that the percentage deflection increase at the end of fatigue loading was almost the same for all beams which implies that damage accumulation is independent from the prestress level. CFRP strain variation at mid‐span indicated the occurrence of deboning during the initial cycling of beams prestressed to 0 and 20% while no signs of bond degradation were observed in the other beams. Therefore, prestressing the CFRP strips was shown to enhance the bonding properties and resulted in an overall CFRP strain increase at the completion of the fatigue loading. For all beams, steel and concrete strains as well as crack widths at mid‐span increased rapidly in the initial 500 cycles followed by stabilized linear increase trends for the rest of the fatigue loading.

Select this Article		Performance of End‐Anchorage Systems for RC Beams Strengthened in Shear with Epoxy‐Bonded FRP Amir Mofidi, Omar Chaallal, Brahim Benmokrane, and Kenneth Neale Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000263 Posted ahead of print 18 October 2011 Full Text: \| Download PDF
	+ -	Show Abstract This paper presents the results of an experimental investigation on the performance of full‐scale reinforced concrete (RC) T‐girders strengthened in shear using externally bonded FRP (EB FRP) U‐jackets end‐anchored with different systems. Debonding of FRP, particularly in shear, is a major failure mode when using FRP sheets to strengthen concrete structures. Design code provisions and guidelines related to shear strengthening of RC beams using EB FRP suggest the use of end‐anchorage systems to prevent FRP debonding. However, no guidelines are available for the design and effectiveness of end‐anchorage systems. The main objective of this study is to evaluate the effectiveness of different end‐anchorage systems for RC beams strengthened using EB FRP methods. To this end, nine tests were performed on 4520‐mm‐long RC T‐beams. Four specimens were strengthened in shear using EB FRP methods with various end‐anchorage systems, and their performance was compared with similar specimens strengthened with: (i) EB FRP with no anchorage; (ii) near‐surface‐mounted (NSM) FRP rods; and (iii) embedded through‐section (ETS) FRP rods. The results of this study reveal that specimens retrofitted with EB FRP methods and properly designed end‐anchorage systems can achieve a superior contribution to shear resistance compared with specimens strengthened using EB FRP with no anchorage, NSM, or ETS methods.

Select this Article		The Effect of Warm Temperatures on Externally Bonded FRP Strengthening T. J. Stratford and L. A. Bisby Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000260 Posted ahead of print 18 October 2011 Full Text: \| Download PDF
	+ -	Show Abstract Fiber‐reinforced polymer (FRP) plate strengthening relies critically upon the adhesive that is used to bond it to the existing structure. A typical two‐part ambient cure epoxy adhesive for structural strengthening has a glass transition temperature that is around 40°C to 70°C, but the stiffness and strength of the adhesive typically decrease at temperatures somewhat below this characteristic temperature. This paper investigates the implications of the changes in adhesive properties at warm temperatures (< 100°C) for FRP strengthened beams, through short‐term experimental and analytical work. Tests were conducted on FRP‐strengthened steel beams subjected to sustained load and increasing temperature; the results, however, are also relevant to strengthened concrete beams. Digital image correlation was used to measure the slip between the strengthening plate and beam, and hence to observe the behavior of the adhesive joint. A bond analysis was also developed to predict the slip across the adhesive joint at elevated temperature, based upon the glass transition characteristics of the adhesive measured using dynamic mechanical analysis. The analysis allows the response of the strengthened beams to warm temperatures to be examined in further detail. Both the experimental and analytical results show that substantial slip can occur between the plate and beam at temperatures over 40°C. As the temperature increases and the adhesive softens, a greater length of adhesive joint is required to transfer load from the plate to the beam, resulting in an increase in slip that eventually causes debonding of the plate from the beam.

Select this Article		Affect of Hot‐Wet Aging on the Pin‐Bearing Strength of a Pultruded Material with Polyester Matrix B. Zafari and J. T. Mottram Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000258 Posted ahead of print 23 September 2011 Full Text: \| Download PDF
	+ -	Show Abstract This paper presents test results to show the effect of hot‐wet conditioning on the pin‐bearing strength of a pultruded fiber reinforced polymer material. Knowledge of this strength property, taking account of any reduction over the service lives of structures, is required to reliably calculate bearing strength when designing bolted connections. Pin‐bearing strength is determined using an in‐house test method with batches of nominally identical specimens, cut from the web of a 203 × 203 × 9.53 mm wide flange shape. This shape is from the 1525 series of Creative Pultrusion Inc., having a polyester based matrix. Specimens were immersed prior to strength testing under water for 3000 hours at the constant temperature of 40° C. The paper discusses the accelerated aging protocol and its relation to service life, and an explanation is given to why the material was aged for an unknown number of service years. Variables in the test matrix are the direction of the bearing force (0°, 45° and 90° to the direction of pultrusion) and plain pin diameter (four sizes from 9.7 mm to 25.4 mm). Comparing aged pin‐bearing strengths with equivalent strengths for non‐aged material it is found that the average reduction in characteristic strength (calculated in accordance with Eurocode 0) of the 12 batches, is in the range of 18 to 31%. The extent of strength reduction is found to be independent of pin size, except when the diameter is 25.4 mm. For the 0° situation a comparison is made between the characteristic strengths for the four pin diameters determined using BS EN 1990:2002 and ASTM D7290 to show that the latter Weibull distribution values are lower, and by 4 to 18%.

Select this Article		Oxygen Permeability of FRP‐Concrete Repair Systems Chandra Khoe, Rajan Sen, F. ASCE, and Venkat R. Bhethanabotla Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000257 Posted ahead of print 23 September 2011 Full Text: \| Download PDF
	+ -	Show Abstract Fiber reinforced polymers are increasingly being used for repairing corrosion‐damaged concrete structures. The performance of the repairs is critically dependent on the oxygen permeability of the FRP‐concrete system. This paper presents results of an experimental study in which the oxygen permeation of concrete and FRP‐concrete systems were determined. In the study, concrete specimens with three different water‐cementitious ratios were initially tested. Subsequently, unidirectional one and two layer carbon and fiberglass material were bonded to the concrete surface and the oxygen permeation of the FRP‐concrete systems determined. The results showed that there was a significant reduction in the oxygen permeation of concrete after FRP had been bonded. The best performance was obtained for FRP bonded to a concrete with the highest water‐cementitious ratio. An expression for the equivalent thickness of FRP‐concrete systems was derived using Fick's law. This facilitates the evaluation of the effectiveness of alternate FRP‐concrete corrosion repair schemes.

Select this Article		An Attempt for Seismic Retrofit of Existing Sub‐Standard RC Members under Reversed Cyclic Flexural Effects Caglar Goksu, Alper Polat, and Alper Ilki Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000256 Posted ahead of print 23 September 2011 Full Text: \| Download PDF
	+ -	Show Abstract Many existing reinforced concrete (RC) sub‐standard structures in seismically active regions, designed and/or constructed improperly, or constructed before up‐to‐date seismic design codes, are in urgent need of seismic retrofitting. Besides financial issues, disturbance to the occupants and functions of the structures are among obstacles for seismic retrofitting. Utilization of fiber reinforced polymer (FRP) composites can reduce disturbance to the occupants and hindrance of the functions of the structures remarkably. In this study, the applicability of flexural seismic retrofitting using carbon FRP pre‐cured laminates and rods is investigated experimentally. In seismic retrofitting, the key issue is the effect of reversed cyclic actions, which impose cycles of compression and tension stresses on the FRP reinforcement. Two major issues examined in the study are i) the anchorage of FRP pre‐cured laminates/rods used for cyclic flexural strengthening to the low strength concrete support (foundation) and ii) the efficiency of the presented flexural seismic retrofit technique for the case of low strength concrete members subjected to reversed cyclic loading conditions. Furthermore, the flexural strengths of the reference and retrofitted specimens are predicted analitically. The accuracy of the predictions varied depending on the assumed and actual failure modes of the specimens.

Select this Article		Residual Behavior of Shear‐Repaired Concrete Beams Using CFRP Sheets Subjected to Elevated High Temperatures Yail J. Kim, Amer Hmidan, and Kyoung‐Kyu Choi Journal of Composites for Construction doi:http://dx.doi.org/10.1061/(ASCE)CC.1943-5614.0000244 Posted ahead of print 3 August 2011 Full Text: \| Download PDF
	+ -	Show Abstract This paper presents the residual behavior of unreinforced concrete beams repaired with carbon fiber reinforced polymer (CFRP) sheets in shear subjected to elevated temperatures up to 200°C. An experimental program is conducted to examine the effects of high temperature exposure on the response of constitutive materials, adhesive‐concrete interface, and shear‐repaired beams. All test beams are notched to represent various levels of shear deficiency. A predictive modeling approach is proposed based on classical laminate theory. Elevated temperatures influence the capacity and interfacial characteristics of the repaired beams. Temperature effects, however, are not significantly correlated with the formation of diagonal tension cracks (shear crack) and their propagation rate. Shear resistance of the CFRP is found to be independent of high temperature exposure because of the load‐resisting mechanism associated with crack‐plane strains and shear‐failure angle.