Browsing Cold-Formed Steel Research Consortium (CFSRC) by Date
Now showing 1 - 20 of 187
Results Per Page
ItemDistortional Buckling of Cold-Formed Steel Columns(2000) Schafer, B.W.Research on the distortional buckling of cold-formed steel columns, primarily C and Z shapes is summarized in this document. ItemTest Verification of the Effect of Stress Gradient on Webs of Cees and Zee Sections(2002) Schafer, Ben; Yu, ChengThis report details the work performed under a research grant funded by the American Iron and Steel Institute (AISI) and the Metal Building Manufacturers Association (MBMA) entitled “Test Verification of the Effect of Stress Gradient on Webs of Cee and Zee Sections.” The project evolved in response to the inconclusive nature of existing test data on Cees and Zees in bending and the need for a set of simple repeatable tests on industry standard sections that account for typical details in current practice and provide the actual bending capacity in local buckling. Findings and recommendations from the research follow. ItemDistortional Buckling of Cold-Formed Steel Members in Bending(2005) Yu, Cheng; Schafer, Benjamin W.Laterally braced cold-formed steel beams generally fail due to local and/or distortional buckling in combination with yielding. For many cold-formed steel (CFS) studs, joists, purlins, or girts, distortional buckling may be the predominant buckling mode. However, distortional buckling of CFS beams remains a largely unaddressed problem in the current North American Specification for the Design of Cold-Formed Steel Structural Members (NAS). Further, adequate experimental data on unrestricted distortional buckling in bending is unavailable. Therefore, two series of bending tests on industry standard CFS C and Z-sections were performed and presented in this dissertation. The testing setup was carefully designed in the first series of tests (Phase 1) to allow local buckling failure to form while restricting distortional and lateral-torsional buckling. The second series of tests (Phase 2) used nominally identical specimens to Phase 1 tests, and a similar testing setup. However, the corrugated panel attached to the compression flange was removed in the constant moment region so that distortional buckling could occur. The experimental data was used to examine current specifications and new design methods. Finite element modeling in ABAQUS was developed and verified by the two series of bending tests and then applied to analyze more CFS beams. ItemExperiments on Rotational Restraint of Sheathing(2007) Schafer, B.W.; Sangree, R. H.; Guan, Y.A series of cantilever tests on joist-sheathing assemblies were conducted to determine the rotational restraint that sheathing provides to the compression flange of a floor joist in bending. This rotational restraint, which is characterized by the stiffness k?, can partially or fully retard distortional buckling. Distortional buckling is a mode of instability in which the flange undergoes rotation about the flange/web juncture of a member and the web locally bends. This mode of buckling has recently been recognized as a separate strength limit state in the North American Specification and design rules for its prediction adopted. ItemSteel Sheet Sheathing Options for CFS Framed Shear Wall Assemblies Providing Shear Resistance(2007-10-31) Yu, Cheng; Vora, Hitesh; Dainard, Tony; Tucker, Jimmy; Veetvkuri, PradeepIn cold-formed steel construction, stud walls covered with steel sheet sheathing is an available option to resist lateral loads such as those caused by wind and earthquakes. The current American Iron and Steel Institute (AISI) Standard for Cold-Formed Steel Framing – Lateral Design 2004 Edition provides nominal shear strength for a limited range of steel sheet sheathed shear wall configurations. This report presents a research project developed to add values for 0.030-in. and 0.033-in. steel sheet sheathed shear walls with 2:1 and 4:1 aspect ratios and 0.027-in. sheet steel shear walls with 2:1 aspect ratio and 6-in., 4-in., 3-in., and 2-in. fastener spacing at panel edges. For all specimen configurations, the steel sheet sheathing was installed on one face of the wall. The test program consisted of two series of shear wall tests. The first series focused on determining the nominal shear strength for wind loads for which monotonic tests in accordance with ASTM E564 standard were performed. The second series of tests addressed the nominal shear strength for seismic loads for which the reversed cyclic tests using CUREE protocol were conducted. The research was sponsored by AISI and SSMA, and was performed at University of North Texas. ItemAnalytical Study on Rotational Restraint of Sheathing(2008) Guan, Y.; Schafer, B.W.Building upon a previous set of experiments performed to determine connection rotational restraint provided by sheathing in cold-formed steel floor joists, this study investigates the reliability of reported connection rotational stiffness values. Key assumptions made by the experimental researchers during testing and post processing of experimental data are explored. Effects observed but not measured during testing, including fastener pullout failure and construction flaws, are also examined. ItemDirect Strength Design of Cold-Formed Steel Members with Perforations(2008) Moen, Cristopher DennisCold-formed steel (CFS) structural members are commonly manufactured with holes to accommodate plumbing, electrical, and heating conduits in the walls and ceilings of buildings. Current design methods available to engineers for predicting the strength of CFS members with holes are prescriptive and limited to specific perforation locations, spacings, and sizes. The Direct Strength Method (DSM), a relatively new design method for CFS members validated for members without holes, predicts the ultimate strength of a general CFS column or beam with the elastic buckling properties of the member cross- section (e.g., plate buckling) and the Euler buckling load (e.g., flexural buckling). This research project, sponsored by the American Iron and Steel Institute, extends the appealing generality of DSM to cold-formed steel beams and columns with perforations. ItemInelastic Bending Capacity in Cold-Formed Steel Members(2008) Shifferaw, Yared; Schafer, B.W.The enclosed research report has been prepared for the AISI as supporting material for proposed additions to the AISI Specification (AISI-S100-07) with respect to inelastic bending of cold- formed steel flexural members. In particular, an extension to the Direct Strength Method of Appendix 1 of AISI-S100-07 is proposed which allows for design capacities to exceed My (and approach Mp) as a function of the slenderness in the local-global or distortional modes. ItemAISI Design Methods for Sheathing Braced Design of Wall Studs in Compression(2008) Schafer, B.W.; Vieira, L.; Iourio, O.This is an informal progress report document summarizing recent work on the development of a design method for sheathing braced design of wall studs with dissimilar sheathing. This document focuses on only one aspect of the ongoing work: a critical review of existing design methods for wall studs in compression. The document concludes with a list of limit states that should potentially be checked for a sheathed wall stud in compression. (Progress on other aspects of the project including the experimental work is ongoing, but not reported in this document.) The goals of this document include: to fully understand the technical basis for existing and past design methods, to resolve the local vs. diaphragm stiffness design debate, to understand what existing methods do well and what they miss with respect to design, and to lay the ground work for the creation of a comprehensive design method for a sheathed wall stud. ItemCold-Formed Steel Bolted Connections Without Washers on Oversized and Slotted Holes Phase 1(2008-07) Yu, Cheng; Sheerah, IbraheemIn cold-formed steel construction, bolted connections without washers for either oversized or short slotted holes may significantly expedite the building process and lower the cost. However, the current design specification does not include provisions for such connections, and washers are required to be installed for oversized holes or short slotted holes. The research presented in this report aims to experimentally investigate three typical failure modes in cold-formed steel bolted connections with the non-washer and oversized configurations. The three failure modes have been observed: sheet shear failure, sheet bearing failure, and fracture failure of the net section in the connected sheet. The research project consists of two phases. In Phase 1 the sheet shear and bearing failures will be studied, and in Phase 2 the fracture failure will be investigated. The test matrices include a full range of connection configurations covering various steel sheet thicknesses from 30 mil to 118 mil, different connection types of single and double shear using ASTM A307 and A325 bolt types, and high and low ductile steels. ItemSteel Sheet Sheathing Options for Cold-Formed Steel Framed Shear Wall Assemblies Providing Shear Resistance - Phase 2(2009) Yu, Cheng; Chen, YujieMonotonic and cyclic tests on cold-formed steel shear walls sheathed with steel sheets on one side were conducted to (1) verify the published nominal shear strength for 18-mil and 27-mil steel sheets; and (2) investigate the behavior of 6-ft. wide shear walls with multiple steel sheets. This project is the continuation of a completed project titled “Steel Sheet Sheathing Options for Cold-Formed Steel Framed Shear Wall Assemblies Providing Shear Resistance” by Yu (2007). This Phase 2 project confirms the discrepancy in the published nominal strength of 27-mil sheets discovered by the Phase 1 project, and proposes new values. The project also finds disagreement on the nominal strength of 18-mil sheets for seismic design, which requires further research. For the 6-ft. wide shear walls, this project indentifies special seismic detailing to prevent potential damage on studs while improving the strength and ductility of the shear walls. This report provides detailed information on the test setup, test results, and analyses. ItemCold-Formed Steel Bolted Connections Using Oversized and Slotted Holes without Washers Phase 2(2010-03-18) Yu, Cheng; Xu, KeIn cold-formed steel (CFS) construction, bolted connections without washers for either oversized or slotted holes may significantly expedite the installation process and lower the cost. The North American Specification for the Design of Cold-Formed Steel Structural Members requires washers to be installed in bolted connections with oversized or slotted holes. A research project (Phase 1) sponsored by American Iron and Steel Institute was recently completed at the University of North Texas (UNT) that investigated the performance and strength of bolted CFS connections with oversized and slotted holes without using washers. The research presented in this report is the Phase 2 project in which the bolted CFS connections were studied in a broader respect in terms of the failure mechanism, the material thickness, and the hole configurations. Combined with Phase 1 results, the Phase 2 report gives a comprehensive evaluation of the behavior and strength of bolted CFS connections with oversized and slotted holes without using washers. Revisions to the existing AISI North American Specification requirements for bolted connections are proposed to account for the reduction in the connection strength caused by the oversized and slotted hole configurations without washers. ItemBehavior and Design of Sheathed Cold-Formed Steel Stud Walls under Compression(2011) Vieira, Luiz Carlos Marcos JuniorCold-formed steel may be used to frame the walls, floors, and roofs of modern buildings. The individual cold-formed steel members (studs) have sheathing attached to provide appropriate architectural enclosures. This sheathing also serves to brace the cold- formed steel studs under load. This thesis is dedicated to the study of sheathed cold- formed steel walls under axial loads. ItemCFS-NEES Building Structural Design Narrative(2011) Madsen, R. L.; Nakata, N.; Schafer, B.W.The NSF sponsored CFS-NEES1 project R-CR: Enabling Performance-Based Seismic Design of Multi-Story Cold-Formed Steel Structures project was undertaken to study the behavior, particularly seismic behavior, of light-framed structures using cold-formed steel cee-sections as the primary gravity load carrying elements with wood structural panel diaphragms and shearwalls as the primary lateral load resisting system. Devco Engineering, Inc. was selected to develop design calculations and drawings for the structure based on criteria determined by the research team. Input on the details of design was also sought from industry professionals through the Industry Advisory Board (IAB)2. The details developed in the design phase will be studied via component and full-scale shake table testing of the structure. This report discusses the design of the gravity and lateral systems for the CFS-NEES building. Specific calculations and drawings are attached herewith as appendices for reference. ItemExperiments on the Stability of Sheathed Cold-Formed Steel Studs Under Axial Load and Bending(2012) Peterman, Kara D.This report provides test and analysis results for a typical cold-formed steel (CFS) stud as employed in light steel framing for a building. Specifically, tests are conducted on a 362S162-68 (50 ksi) stud connected to 362T162-68 (50ksi) track with varying combinations of sheathing connected to the two flanges. Loading consists of both axial load and a directly applied horizontal load to induce major-axis bending of the stud (and torsion due to the shear center of the stud). The sheathing configurations studied are intended to capture various stages of construction and final form and include: no sheathing; one-sided sheathing with Oriented Strand Board (OSB); and two-sided sheathing with OSB and gypsum board, or only OSB on the two sides, or only gypsum board on the two sides. The combinations of axial load (P) and bending load (M) studied are intended to capture nearly the complete P-M space. ItemPull-through Tests on OSB and Gypsum Board(2012) Vieira, L.V.; Sampson, I.; Van Doren, M.The objective of this report is to provide pull-through stiffness and capacity for common fasteners used in cold-formed steel attached to oriented strand board or gypsum. A total of 35 tests were conducted at dry, humid, and normal conditions for the sheathing. The tests, which were conducted in uniaxial tension, attach the actuator to the tip of a screw and pull the fastener head through a 4 in. x 4 in. board of sheathing supported by a stiff HSS tube with a circular opening 2 in. in diameter. Mean pull-through strength in OSB is 286 lbf with an initial stiffness of 5790 lbf/in. under normal conditions but decreases for dry or humid board. Mean pull through strength in gypsum is 96 lbf with an initial stiffness of 1911 lbf/in. under normal conditions but decreases substantially for dry or humid conditions. The tested values are intended for use in the prediction of the pull-through failure mode which is commonly observed in cold-formed steel framed walls and floors with sheathing. ItemMoment-Rotation Characterization of Cold-Formed Steel Beams(2012) Ayhan, D.; Schafer, B.W.The objective of this study is to provide a prediction method for characterizing the complete moment-rotation (M-!) response of cold-formed steel (CFS) members in bending. The work is an ancillary effort related to the National Science Foundation funded Network for Earthquake Engineering Simulation (NEES) project: CFS-NEES (www.ce.jhu.edu/bschafer/cfsnees). The goal of CFS-NEES is to enable performance-based seismic design for cold-formed steel framed buildings. A basic building block of performance-based seismic design is nonlinear structural analysis. For cold-formed steel members, which suffer from local and distortional buckling, existing codes provide peak strength and approximations for stiffness loss prior to peak strength, but no estimation of post-peak M-! behavior. Complete M-! response is necessary for nonlinear structural analysis of CFS framed buildings. In this research, existing data, obtained by experiments and finite element analysis, are processed to examine the complete M-! response in cold-formed steel beams. Using a modification of the simplified model introduced in ASCE 41 for pushover analysis, the M-! response is parameterized into a simple multi-linear curve. The parameters include the initial stiffness, fully effective limit, reduced pre-peak stiffness, peak moment, post-peak plateau, and post-peak rotation at 50% of the peak moment. It is shown herein that the parameters of this multi-linear M-! curve may themselves be readily predicted as a function of either the local slenderness or distortional slenderness of the cross-section, as appropriate. Accuracy of the proposed M-! approximation is assessed. The impact of utilizing the full M-! response in a single and multi-span CFS beam is demonstrated. The proposed prediction method for M-! provides a necessary step in the development of nonlinear structural analysis of CFS systems. ItemFastener Spacing Study of Cold-Formed Steel Wall Studs Using Finite Strip and Finite Element Methods(2012) Post, BrianThis study aims to compare the finite element and finite strip methods as they are used to perform buckling analyses of cold-formed steel wall studs. Load-bearing cold-formed steel studs are becoming more common as a building material in both commercial and residential structures. Current design methods allow for the determination of the capacity of single studs under compression. However, entire wall systems often have sheathing attached, which adds bracing and increases stability. Examples of sheathing materials include oriented-strand board (OSB), gypsum, and plywood. Recent work by Vieira (2011) has led to the development of a method to calculate the contributions of sheathing and fasteners to overall wall strength. The equations use various parameters of a wall system and calculate spring stiffness values that can be applied to the fasteners along a stud for three degrees-of-freedom: in the plane of the board (kx), out of the plane of the board (ky), and rotational (kφ). ItemTest Report on Cold-Formed Steel Shear Walls(2012) Liu, P.; Peterman, K.D.; Schafer, B.W.The objective of report is to detail recent cyclic tests on cold-formed steel (CFS) framed shear walls sheathed with Oriented Strand Board (OSB). The tests details are motivated from shear walls designed for a two-story ledger-framed building that will undergo full-scale shake table testing as part of the National Science Foundation funded Network for Earthquake Engineering Simulation (NEES) project: CFS-NEES (www.ce.jhu.edu/bschafer/cfsnees). Monotonic and cyclic (CUREE protocol) tests are conducted on 4 ft?9 ft (1.22m?2.74 m) and 8 ft?9 ft (2.44m?2.74 m) shear walls utilizing 54 mil (1.37mm) back-to-back chord studs and 7/16 in. (11.1 mm) OSB sheathing on the exterior. Practical building details studied in the shear wall tests include the impact of (a) ledger track, which is attached to the top of the interior face of the wall, (b) gypsum, which is attached to the interior face of the wall below the ledger track, (c) locations of panel seams, both horizontal and vertical in the OSB, and (d) the impact of differing stud thickness and grade for the field studs. The information will be used to assess current design procedures utilizing AISI-S213-07 and to develop nonlinear (hysteretic) models of the shear walls in the CFS-NEES model building so that full building system performance can be assessed. ItemSheathing Braced Design of Wall Studs(2013) Schafer, B.W.This report provides a summary document and final report for the multi-year project on Sheathing Braced Design of Wall Studs conducted at Johns Hopkins University. This project examined the axial behavior and axial + bending behavior of cold-formed steel stud walls braced solely by sheathing connected to the stud and track flanges. This report is a practical summary of the work: the history of sheathing braced design, derivations of new analytical methods, testing on components and full sheathing-braced walls, modeling of sheathing-braced members, and the development of the proposed design method are all provided in accompanying documents. Here the focus is on the proposed design method and its application.