Practice Periodical on Structural Design and Construction

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Select this Article		Design of Steel Shear Connections for Eccentricity Due to Secondary Bending Moment Yanglin Gong, M. ASCE Practice Periodical on Structural Design and Construction doi:http://dx.doi.org/10.1061/(ASCE)SC.1943-5576.0000131 Posted ahead of print 29 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract Shear connections develop a moment under the rotational demand imposed to them by the supported beam. For single‐angle, double‐angle, and tab to tubular column shear connections, this moment can be obtained through the equations derived from appropriate plastic yieldline mechanisms. The primary application for the moment equations in the design of a connection is that the obtained moment can be used to estimate the load demand on the bolts or/and welds of the connection. This paper illustrated the moment equation method through various examples. Compared with the current empirical approaches in connection design, the proposed equation method is versatile and insightful.

Select this Article		How Strong Is Strong Enough? Howard J. Hill, Ph.D., SE and Gary J. Klein, SE Practice Periodical on Structural Design and Construction doi:http://dx.doi.org/10.1061/(ASCE)SC.1943-5576.0000130 Posted ahead of print 20 March 2012 Full Text: \| Download PDF
	+ -	Show Abstract When a structural element fails, it is often necessary to determine whether or not the element was properly designed, fabricated, constructed and maintained. Among the many things such a determination requires is an appropriate benchmark strength; a capacity that can be compared to the loading that caused the failure to determine whether or not the element met appropriate expectations. Establishing a rational benchmark is complicated by the fact that common industry design, fabrication and construction methods can result in substantial and highly variable deviations of the actual strengths of structural elements relative to the corresponding nominal values. This paper uses First Order Reliability Methods — similar to those used to develop current AISC LRFD steel design provisions — and other methods to arrive at a rational definition of how strong a particular element needs to be in order to be considered strong enough.

Select this Article		Risk and Financial Impacts of Prevention through Design Solutions Sathyanarayanan Rajendran and John Gambatese Practice Periodical on Structural Design and Construction doi:http://dx.doi.org/10.1061/(ASCE)SC.1943-5576.0000129 Posted ahead of print 21 February 2012 Full Text: \| Download PDF
	+ -	Show Abstract Falls from roofs is a significant risk of both construction and maintenance workers. A roof anchor system is the common design solution to eliminate the falling hazard. This paper presents the findings of a case study to serve as a preliminary investigation of the financial impact and risk of roof fall protection solutions. The research began with the selection of a project that featured a roof anchor system and a parapet that does not meet OSHA guardrail height requirements. The intent of the research was to compare the cost of design and installation of the roof anchors and parapet with that of two other design options on the same project: only a parapet that meets the OSHA guardrail requirements; and no anchors or parapet. Data used for the study was collected through interviews of project personnel and reviews of project documentation. The parapet system was found be an expensive, but safer, alternative compared to the roof anchor system. The roof anchor system creates more risk to worker safety due to the extensive amount of temporary fall protection measures required during construction. This requirement puts more workers at risk of injury during installation of temporary guardrails and while working near the leading edge. The roof anchor system indirectly affects worker productivity by at least 15 percent compared to the parapet system. Using this study as a starting point, more research is recommended that examines the costs and risks associated with various prevention through design (PtD) solutions. Such research will assist owners and designers in making informed decisions while choosing PtD solutions.

Select this Article		Alternate Path Method in Progressive Collapse Analysis: Variation of Dynamic and Nonlinear Load Increase Factors Aldo McKay, Kirk Marchand, and Manuel Diaz, M. ASCE Practice Periodical on Structural Design and Construction doi:http://dx.doi.org/10.1061/(ASCE)SC.1943-5576.0000126 Posted ahead of print 28 January 2012 Full Text: \| Download PDF
	+ -	Show Abstract In performing alternative path analyses for checking the potential of a structure to progressive collapse most designers often choose static procedures which tend to be simpler and less labor demanding. As progressive collapse is a dynamic and nonlinear event, the load cases for the static procedures require the use of factors to account for inertial and nonlinear effects. A number of inconsistencies have been identified in the way the existing guidelines applied dynamic and nonlinear load factors to their static approaches. As part of an existing effort to update the existing guidelines, this study looked into the behavior of a variety of reinforced concrete and steel moment frame buildings to investigate the magnitude and variation of the dynamic and nonlinear load increase factors. The study concluded that the factors in the existing guidelines tend to yield overly conservative results which often translate into expensive designs and retrofits. This study identified new load increase factors and proposes a new approach to utilize these factors when performing alternative path analyses for progressive collapse.

Select this Article		R.C. Columns Strengthened with Steel Angles and Battens: Experimental Results and Design Procedure Giuseppe Campione Practice Periodical on Structural Design and Construction doi:http://dx.doi.org/10.1061/(ASCE)SC.1943-5576.0000125 Posted ahead of print 19 December 2011 Full Text: \| Download PDF
	+ -	Show Abstract In this paper, an analytical model is presented for the design of an axially loaded strengthened reinforced concrete (R.C.) columns with steel angles and battens. Cases of directed and not directed steel angles were considered. The model considers the contribution in confinement pressures due to transverse battens and steel angles and the contribution in term of load carrying capacity of steel angles subjected to axial force and bending moment. An experimental investigation on the compressive behavior of eight short, confined, reinforced concrete columns externally strengthened with steel angles and steel battens with different pitch was carried out and utilized as support for the analytical model. Analytical results here generated were compared with experimental data available in the literature and with those obtained by using the existing analytical models (Cirtek 2001, Eurocode 4 1994, Eurocode 8 2003, Braga et al. 2006). Comparison shows acceptable prediction of the experimental results both in the case of directed and not directed steel angles. Finally, some design rules given by recent codes for the design of this strengthening technique are discussed by using the proposed model.

Select this Article		Trenchless Infrastructure Construction Techniques Used in Colombia John C. Matthews and Juan Carlos Gutierrez Practice Periodical on Structural Design and Construction doi:http://dx.doi.org/10.1061/(ASCE)SC.1943-5576.0000123 Posted ahead of print 16 November 2011 Full Text: \| Download PDF
	+ -	Show Abstract The use of traditional urban infrastructure construction techniques, particularly open‐cut construction, is being used less and less due to the benefits offered by trenchless techniques. These techniques typically reduce the disruption and impact on both the environment (i.e., reduced green house gas emissions) and society (i.e., reduced traffic and pedestrian delays due to road and sidewalk closures). In Colombia, owners such as Empresas Públicas de Medellín E.S.P. (EPM) and Colombian Institute for Subterranean Infrastructure Technologies and Techniques (CISTT) have promoted the use of these technologies in urban areas. The primary techniques used in Colombia for installing and rehabilitating urban infrastructure are pipe bursting, horizontal directional drilling (HDD), cured‐in‐place pipe (CIPP), and microtunneling. Automated decision support tools are available in Colombia to assist designers in selecting technically viable techniques. This paper describes the trenchless techniques used in Colombia, a brief description of a decision support system available for selecting construction methods, and discusses four applications for installing and/or rehabilitating underground utilities through case studies of projects in Colombia.

Select this Article		Verification of the Strength of the Anchor Point of a Fall Arresting and Positioning Systems for Reinforcing Steel Erectors André Lan and Renaud Daigle Practice Periodical on Structural Design and Construction doi:http://dx.doi.org/10.1061/(ASCE)SC.1943-5576.0000122 Posted ahead of print 16 November 2011 Full Text: \| Download PDF
	+ -	Show Abstract For walls of great dimensions, fall protection is problematic. The reinforcing steel erector has to climb on the reinforcement bars to anchor and position himself to do his tasks and to protect himself against falls. Two problems are identified: 1) the selection of a harness, positioning and fall arrest equipment and 2) an anchor point, sufficiently strong for the positioning and the personal fall arrest systems. This paper describes the dynamic fall tests that have been carried out to verify the strength of tied reinforcement used as an anchor point for the fall arresting and positioning systems of reinforcing steel erectors.

Select this Article		Impact of Crew Scheduling on Project Performance Awad S. Hanna, F. ASCE, Aviad Shapira, F. ASCE, Mounir El Asmar, S. M. ASCE, and Craig S. Taylor Practice Periodical on Structural Design and Construction doi:http://dx.doi.org/10.1061/(ASCE)SC.1943-5576.0000121 Posted ahead of print 12 November 2011 Full Text: \| Download PDF
	+ -	Show Abstract Contractors have responded to the growing pressure of owners to shorten project duration by employing a variety of crew scheduling techniques. Unfortunately, only a limited knowledge base exists for determining the impact of different crew schedules on project performance in terms of cost, duration, productivity, and safety. Standard crew schedules include those that require crews to work 40 hours per week, including five eight‐hour days, four ten‐hour days, or a second shift. Overtime schedules are also common, which require crews to work additional hours beyond the standard 40 hours per week. These overtime schedules include five nine‐hour days, six eight‐hour days, or five ten‐hour days. In addition to the standard and overtime schedules, several other crew scheduling techniques have been used successfully by contractors. This paper presents the results of a study on the impact of crew scheduling techniques on overall project performance. The paper identifies the proper application and conditions for successful use of various crew scheduling techniques and provides a comprehensive comparison that outlines a variety of crew scheduling options, along with their impact on labor efficiency, project duration, worker safety, and project cost. Contractors can use the results to aid them in the selection of a scheduling technique to best meet the specific requirements of a project.

Select this Article		Configuration Optimization of Drilled Shafts Supporting Bridge Structures: Three Case Studies Brent Robinson, P.E., M. ASCE, Vinicio Suarez, Mohammed Gabr, P.E., M. ASCE, and Mervyn Kowalsky, P.E., M. ASCE Practice Periodical on Structural Design and Construction doi:http://dx.doi.org/10.1061/(ASCE)SC.1943-5576.0000118 Posted ahead of print 14 September 2011 Full Text: \| Download PDF
	+ -	Show Abstract A common approach to estimate the point of fixity is to utilize the results of a single pile lateral analysis. Although no universal agreement exists as to the definition of the location of the point of fixity, it is generally accepted that its location will impact the computed stresses and displacements of a bridge structure. Work in this study summarizes a method to determine the cantilever's equivalent length of drilled shaft foundation elements supporting a bridge. Results from an equivalent frame model are compared to those for bents modeled using the finite element method and nonlinear soil models for three bridges in North Carolina. Results indicated that the equivalent frame model provides responses that are comparable to those obtained from more rigorous finite element analyses. The study presents the results of the optimization of the support system by reducing the number, or size, of the shafts while maintaining acceptable level of safety.

Select this Article		Seismic Retrofitting for Chord Reinforcement for Unreinforced Masonry Historic Buildings with Flexible Diaphragms J. Kent Hsiao, Ph.D., P.E., S.E., F. ASCE and Jale Tezcan, Ph.D., P.E., M. ASCE Practice Periodical on Structural Design and Construction doi:http://dx.doi.org/10.1061/(ASCE)SC.1943-5576.0000117 Posted ahead of print 9 September 2011 Full Text: \| Download PDF
	+ -	Show Abstract The existing wood‐diaphragm‐to‐masonry‐wall connections in unreinforced masonry (URM) buildings provided very little or insufficient resistance in past earthquakes. Recent strengthening techniques for the connections between the URM walls and the flexible diaphragms concentrate only on the installation of wall anchorages for out‐of‐plane tension forces and shear bolts for in‐plane shear forces. Strengthened chord elements, however, are also essential parts of URM buildings to resist earthquakes. This paper proposes seismic rehabilitation techniques where steel angles are used as chord reinforcement. A practical design example is presented, where chord axial forces caused by in‐plane diaphragm deflections and chord shear flows caused by transverse seismic forces are computed. The computed axial forces and shear flows are to be used in the design of the chord reinforcement and the chord shear connections, respectively.

Select this Article		Prediction of Inelastic Mechanisms Leading to Seismic Failure of Interior Reinforced Concrete Beam‐Column Connections Nilanjan Mitra and Pijush Samui Practice Periodical on Structural Design and Construction doi:http://dx.doi.org/10.1061/(ASCE)SC.1943-5576.0000115 Posted ahead of print 31 August 2011 Full Text: \| Download PDF
	+ -	Show Abstract Inelastic mechanisms leading to failure in interior reinforced concrete beam column (RCBC) connections, designed based on concept of strong column weak beam philosophy, are primarily failure of the joint region and yielding of longitudinal reinforcement in beams. Two novel easy to use probabilistic methodologies have been developed in this manuscript which can determine the occurrence of either of these inelastic mechanisms leading to failure with sufficient accuracy given the geometric, material and loading parameters of an experimental investigation. Relevance Vector Machine method, a machine learning methodology based on a Bayesian formulation and resulting in a sparse representation, was utilized to develop one model. Another model developed was Binomial Logistic Regression, which can not only relate the qualitative event of inelastic mechanism resulting in failure initiation with a number of experimentally obtained independent parameters but can also quantify the relative importance of each of these independent parameters. Both these methods shows good predictive efficiency and can be utilized by a designer, engineer or researcher to obtain a preliminary probabilistic estimate of inelastic mechanisms leading to failure of Interior RCBC connections. Comparative evaluations of utilizing these two models have also been presented in the manuscript.

Select this Article		Accounting for Architectural Demands and Construction Phase in Structural Design M. Branco, M. R. Arruda, and L. Murteira Practice Periodical on Structural Design and Construction doi:http://dx.doi.org/10.1061/(ASCE)SC.1943-5576.0000114 Posted ahead of print 18 August 2011 Full Text: \| Download PDF
	+ -	Show Abstract The structural design of a three‐story building in Palmela, near Lisbon, Portugal, is analyzed. Due to architectural constraints, the main façade of the first floor was designed in a setback of the second floor, which created a 13.0m (42.6 ft) span between supports. To comply with deflection requirements a Vierendeel girder was projected between the second and third floor slabs. Taking advantage of the reduced size of the structure and therefore low computation demand, two non‐linear analyses were conducted. To account for the effect of creep in the construction phase, a physically non‐linear analysis was performed. Furthermore, the second order effect on the vertical elements was accounted for through a geometrically non‐linear analysis. The non‐linear analyses allowed for a more slender and cost‐efficient design when compared with values obtained from the traditional abacus to account for viscoelasticity.

Select this Article		Optimal Structural Design of Circular Rotationally Moulded above Ground Polyethylene Water Storage Tanks D. L. Beneke, J. R. Thumkunta, and D. J. Koen Practice Periodical on Structural Design and Construction doi:http://dx.doi.org/10.1061/(ASCE)SC.1943-5576.0000080 Posted ahead of print 8 September 2010 Full Text: \| Download PDF
	+ -	Show Abstract Rotationally moulded polyethylene water storage tanks have been produced since the 1950's when the technology became available for this manufacturing process. For circular tanks manufactured in this way, the traditional method of design has been based on hand calculations considering internal hydrostatic pressure from the stored liquid as the primary applied load. This study presents the results of the optimal structural design of 16 circular polyethylene water tanks of various sizes. Based on the results derived, optimal design recommendations for these tank structures are provided when both hydrostatic pressure and wind loads are applied.

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