The Experts below are selected from a list of 60 Experts worldwide ranked by ideXlab platform
Gregory J Hancock - One of the best experts on this subject based on the ideXlab platform.
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effect of flange restraints on shear Tension Field Action in cold formed c sections
Journal of Constructional Steel Research, 2017Co-Authors: Cao Hung Pham, Dmitry Zelenkin, Gregory J HancockAbstract:Abstract The recently incorporated Direct Strength Method (DSM) rules for shear in the North American Specification for Cold-Formed Steel Structural Members (NAS S100:2012) consist of design equations for unperforated sections with and without Tension Field Action (TFA). The TFA is mobilised as a result of the development of diagonal Tension due to the full depth bolt restraints. The design shear equations based on a reduction factor α to account for reduced TFA were proposed by Pham and Hancock in cases of partly bolted connections with lateral flange restraints. This paper presents an experimental program to further investigate the TFA of cold-formed C-sections in shear. A total of twelve tests were carried out at the University of Sydney. Three different bolted connection configurations were chosen with and without lateral restraints of the top flanges at the supports. Numerical simulations using the Finite Element Method (FEM) were also performed to validate test results and extend data range. For tests without lateral flange restraints, combined twisting and shear failure modes were observed. The lack of lateral flange restraint leads to a significant reduction of the ultimate load especially when more bolts were removed. Based on these experimental and FEM modelling data, a further reduction factor β dependent upon the slenderness of the sections is introduced in this paper to account for the lack of lateral flange restraint along with the previously proposed reduction factor α which accounts for bolt reduction.
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direct strength design of cold formed c sections for shear and combined Actions
Journal of Structural Engineering-asce, 2012Co-Authors: Cao Hung Pham, Gregory J HancockAbstract:In order to extend the Direct Strength Method (DSM) of design of cold-formed sections to shear, and combined bending and shear, a research program has been performed recently at the University of Sydney. This includes evaluation and calibration of DSM design rules for shear and combined Actions when applied to an extensive series of purlins tested at the University of Sydney, as well as shear only and combined bending and shear tests on channel sections. The paper summarises this research, as well as making proposals for shear, and combined Actions. Two features researched are the effect of full section shear buckling (as opposed to web only shear buckling), and Tension Field Action. Full section buckling is a feature of the DSM but requires software that can evaluate full sections for shear. Methods for doing this are summarised in the paper.
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Tension Field Action for cold formed sections in shear
Journal of Constructional Steel Research, 2012Co-Authors: Cao Hung Pham, Gregory J HancockAbstract:Abstract For shear, the design of sections for strength is usually governed by the web plate subjected to shear force and undergoing shear buckling, or yielding in shear or a combination of the two. For webs with relatively high depth-to-thickness ratios, the shear stress distribution in the web after buckling changes and significant post-buckling strength may occur as a result of the development of a diagonal Tension which is called “Tension Field Action” (TFA). Recently, the full set of shear test results for the plain lipped C- and SupaCee® sections performed at the University of Sydney shows that the post-buckling strength was attributed to TFA which was provided by the increased transverse restraints created by bolted connections attached to loading stiffeners over the full depth of the web panel at the supports and loading point. This improved the post-buckling strengths of the web in shear. Firstly, the results of finite element nonlinear simulations are compared with tests where bolted connections not over the full depth of the web panel were used to validate the FE method. Then the range of test data described previously is extended using finite element models, by reducing the bolting at support and loading points in the test data to provide further guidance on the availability of TFA in particular. Design equations are provided for Tension Field Action.
Michel Bruneau - One of the best experts on this subject based on the ideXlab platform.
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design of steel plate shear walls considering boundary frame moment resisting Action
Journal of Structural Engineering-asce, 2009Co-Authors: Michel BruneauAbstract:Conventional design of steel plate shear walls (SPSWs) assumes that 100% of the story shear is resisted by each infill panel. Following this approach, strength provided by the boundary frame moment resisting Action, which provides the SPSW with overstrength, is neglected. While this design assumption has a positive impact on seismic performance of SPSWs, no analytical work has been done to quantify the magnitude of this overstrength in general terms. Such preliminary work is conducted in this paper. Based on plastic analysis of SPSWs, this paper investigates the relative and respective contributions of boundary frame moment resisting Action and infill panel Tension Field Action to the overall plastic strength of SPSWs, followed by a proposed procedure to make use of the strength provided by the boundary frame moment resisting Action. Procedures for design of SPSWs having weak infill panels are also developed in this paper. Then, results from a series of time history analyses using validated models are presented to compare the seismic performances of SPSWs designed using different design assumptions. Future work needed to provide greater insight on SPSW designs is also identified.
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testing of special lys steel plate shear walls
2004Co-Authors: Darren Vian, Michel BruneauAbstract:An experimental program of steel panel shear walls is outlined and some results are presented. The tested specimens utilized low yield strength (LYS) steel infill panels and reduced beam sections (RBS) at the beam-ends. Two specimens make allowances for penetration of the panel by utilities, which would exist in a retrofit situation. The first, consisting of multiple holes, or perforations, in the steel panel, also has the characteristic of further reducing the corresponding solid panel strength (as compared with the use of traditional steel). The second such specimen utilizes quarter-circle cutouts in the panel corners, which are reinforced to transfer the panel forces to the adjacent framing. INTRODUCTION The selection of Steel Plate Shear Walls (SPSWs) as the primary lateral force resisting system in buildings has increased in recent years as design engineers discover the benefits of this option. Its use has matured since initial designs, which did not allow for utilization of the post-buckling strength, but only elastic and shear yield plate behavior. This design approach typically resulted in the selection of a relatively thick panel for the infill. A large plate thickness, while producing a stiff structure that would reduce displacement demand during a seismic event, would also induce relatively large forces on the surrounding frame members, which must be detailed accordingly to ensure adequate performance. Research conducted by Thorburn et al. (1983) supported the SPSW design philosophy that reduced plate thickness by allowing the occurrence of shear buckling. After buckling, lateral load is carried in the panel via the subsequently developed diagonal Tension Field Action. Smaller panel thicknesses also reduce forces on adjacent members, resulting in more efficient framing designs. Research programs at various universities have furthered the understanding of thin plate SPSWs (e.g., Lubell et al., 2000; Driver et al., 1997; Caccese et al., 1993). However, some obstacles still exist that may impede further widespread acceptance of this system. For example, using the yield stress for typically available steel material, the panel thickness as required by a given design situation may often be much thinner than plate typically available from steel mills. In a case such as this, using the minimum available plate thickness would result in a large difference in panel forces from that required by calculations. Attempts at alleviating this problem were recently addressed by the use of light-gauge, cold-formed steel panels, in a new application by Berman and Bruneau (2003). Xue and Lu (1994) suggested additional means of reducing demand on framing adjacent to an SPSW, including the connection of the infill panel to only the beams in a 1 Ph.D. Candidate, Department of Civil, Structural, and Environmental Engineering, University at Buffalo, Buffalo, NY, USA. Email: vian@eng.buffalo.edu 2 Professor, Department of Civil, Structural, and Environmental Engineering, University at Buffalo, Buffalo, NY, USA. Email: bruneau@mceermail.buffalo.edu moment frame. However, more work is required to ensure the viability of the SPSW system in a wide range of situations. The University at Buffalo (UB) and the Multidisciplinary Center for Earthquake Engineering Research (MCEER) initiated a co-operative experimental program with National Taiwan University (NTU) and the National Center for Research on Earthquake Engineering (NCREE) in order to further address the above issues with regards to SPSW performance. A description of the test program and presentation of results follows below. EXPERIMENTAL PROGRAM A total of three single bay, single story LYS SPSW specimens were designed by the researchers at UB, fabricated in Taiwan, and subjected to quasi-static cyclic testing in the NCREE laboratory at NTU. The frames measured 4000mm wide and 2000mm high between member centerlines, and consisted of 345MPa steel members. The infill panels produced by China Steel were 2.6mm thick, LYS steel plates with an initial yield stress of 165MPa, and ultimate strength of 300MPa, important properties that may aid in alleviating over-strength concerns mentioned above. All specimens also have a beam-to-column connection detail that includes reduced beam sections (RBS) at each end. This detail was designed to ensure all inelastic beam Action would occur at these locations, with the intention of efficient anchoring of infill panel Tension Field forces, as required at the extremes (roof and basement level beams) of a multistory SPSW-retrofitted/designed steel frame. A solid panel specimen is shown schematically in Fig. 1. Figure 1. Typical specimen dimensions. Two specimens tested had solid panels while the remaining two provide utility access through the panels using cutouts. One specimen consisted of a panel with a total of twenty 200mm-diameter holes, or perforations, in an arrangement shown in Fig. 2. Roberts and Sabouri-Ghomi (1992) conducted research investigating the effects of a single perforation in an unstiffened shear panel, leading to some reduction factors that could be applied to the properties of a solid panel, conservatively reducing the stiffness and strength to account for the presence of the perforation. The multiple perforations present in the tested specimen share the common goal of utility access in order to make the SPSW system more acceptable, while also serving as a method of reducing the panel strength and therefore the demand on the surrounding framing. This latter characteristic may prove beneficial in markets that do not have LYS readily available for structural applications. Figure 2. Specimen P before testing. The other specimen allowing for utility penetration is a solid panel, with the top corners of the panel cutout and reinforced to transmit panel forces to the surrounding framing, as shown in Fig. 3 below. This specimen would allow utility access through the wall, while also transmitting forces near that of the solid panel counterpart. Figure 3. Specimen CR before testing. All specimens were tested using a cyclic, quasi-static loading protocol similar to ATC-24. In agreement with the typical testing procedure at NCREE, a displacement-controlled scheme was selected for the entire experimental program. Based on estimates of yield from SAP2000 pushover analyses, the displacement history shown in Fig. 4, was developed and applied horizontally to the center of the top beam using four actuators, as shown in the figures above. The same displacement loading history was used for actuator control of all the specimens tested. -160 -120 -80 -40 0 40 80 120 160 0 3 6 9 12 15 18 21 24 27 30 33 36 Number of Cycles, N In te rs to ry D is pl ac em en t ( m m ) -8% -6% -4% -2% 0% 2% 4% 6% 8% In te rs to ry D rif t ( % ) 2 cycles per amplitude 3 cycles per amplitude
Cao Hung Pham - One of the best experts on this subject based on the ideXlab platform.
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effect of flange restraints on shear Tension Field Action in cold formed c sections
Journal of Constructional Steel Research, 2017Co-Authors: Cao Hung Pham, Dmitry Zelenkin, Gregory J HancockAbstract:Abstract The recently incorporated Direct Strength Method (DSM) rules for shear in the North American Specification for Cold-Formed Steel Structural Members (NAS S100:2012) consist of design equations for unperforated sections with and without Tension Field Action (TFA). The TFA is mobilised as a result of the development of diagonal Tension due to the full depth bolt restraints. The design shear equations based on a reduction factor α to account for reduced TFA were proposed by Pham and Hancock in cases of partly bolted connections with lateral flange restraints. This paper presents an experimental program to further investigate the TFA of cold-formed C-sections in shear. A total of twelve tests were carried out at the University of Sydney. Three different bolted connection configurations were chosen with and without lateral restraints of the top flanges at the supports. Numerical simulations using the Finite Element Method (FEM) were also performed to validate test results and extend data range. For tests without lateral flange restraints, combined twisting and shear failure modes were observed. The lack of lateral flange restraint leads to a significant reduction of the ultimate load especially when more bolts were removed. Based on these experimental and FEM modelling data, a further reduction factor β dependent upon the slenderness of the sections is introduced in this paper to account for the lack of lateral flange restraint along with the previously proposed reduction factor α which accounts for bolt reduction.
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direct strength design of cold formed c sections for shear and combined Actions
Journal of Structural Engineering-asce, 2012Co-Authors: Cao Hung Pham, Gregory J HancockAbstract:In order to extend the Direct Strength Method (DSM) of design of cold-formed sections to shear, and combined bending and shear, a research program has been performed recently at the University of Sydney. This includes evaluation and calibration of DSM design rules for shear and combined Actions when applied to an extensive series of purlins tested at the University of Sydney, as well as shear only and combined bending and shear tests on channel sections. The paper summarises this research, as well as making proposals for shear, and combined Actions. Two features researched are the effect of full section shear buckling (as opposed to web only shear buckling), and Tension Field Action. Full section buckling is a feature of the DSM but requires software that can evaluate full sections for shear. Methods for doing this are summarised in the paper.
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Tension Field Action for cold formed sections in shear
Journal of Constructional Steel Research, 2012Co-Authors: Cao Hung Pham, Gregory J HancockAbstract:Abstract For shear, the design of sections for strength is usually governed by the web plate subjected to shear force and undergoing shear buckling, or yielding in shear or a combination of the two. For webs with relatively high depth-to-thickness ratios, the shear stress distribution in the web after buckling changes and significant post-buckling strength may occur as a result of the development of a diagonal Tension which is called “Tension Field Action” (TFA). Recently, the full set of shear test results for the plain lipped C- and SupaCee® sections performed at the University of Sydney shows that the post-buckling strength was attributed to TFA which was provided by the increased transverse restraints created by bolted connections attached to loading stiffeners over the full depth of the web panel at the supports and loading point. This improved the post-buckling strengths of the web in shear. Firstly, the results of finite element nonlinear simulations are compared with tests where bolted connections not over the full depth of the web panel were used to validate the FE method. Then the range of test data described previously is extended using finite element models, by reducing the bolting at support and loading points in the test data to provide further guidance on the availability of TFA in particular. Design equations are provided for Tension Field Action.
Honggun Park - One of the best experts on this subject based on the ideXlab platform.
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hysteresis model of thin infill plate for cyclic nonlinear analysis of steel plate shear walls
Journal of Structural Engineering-asce, 2010Co-Authors: Inrak Choi, Honggun ParkAbstract:A hysteresis model for thin infill steel plates was developed to evaluate the nonlinear cyclic behavior of steel plate shear walls. Nonlinear finite-element analysis was performed for thin steel plates with a rigid boundary frame. Based on the analysis results, the hysteretic behavior of the infill steel plate was simplified as an equivalent uniaxial stress-strain relationship in the direction of Tension-Field Action. The proposed hysteresis model was implemented in macroscopic analysis models for infill steel plates, i.e., the Tension strip model and equivalent Tension brace model. The proposed method was applied to existing test specimens with various design parameters and loading conditions. The prediction results were compared with the test results.
Laura N Lowes - One of the best experts on this subject based on the ideXlab platform.
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experimental investigation of spsw web plate stress Field development and vertical boundary element demand
Journal of Structural Engineering-asce, 2014Co-Authors: David J Webster, Jeffrey W Berman, Laura N LowesAbstract:AbstractSteel plate shear walls (SPSW) are an efficient but largely underutilized building lateral force resisting system. The system consists of a moment frame (the boundary frame) with slender steel web plates that are welded or bolted inside the boundary frame, forming a diaphragm. The resulting structure resembles a vertical plate girder. The system resists lateral load primarily through Tension Field Action of the postbuckled web plate. The magnitude and orientation of this Tension Field is governed by the relative stiffness of the web plate and boundary frame. The 2010 Seismic Provisions currently require that the Tension Field inclination angle be either 40° or computed using a closed-form equation derived from elastic analysis. It is demonstrated through experimentation and finite-element analyses that the Tension Field inclination may migrate, from an initially low angle under an elastic postbuckled state, toward 45° as the plate is loaded plastically. The resulting flexural demand on the vertica...