Search

This paper examines the accuracy of equations specified by the North American and Australasian steel structures codes for determining the net section tension capacity of a channel brace. It points out that there are three distinct factors affecting the net section efficiency of a cold-formed steel channel brace bolted at the web. These factors include (1) the in-plane shear lag associated with stress concentration around a bolt hole that is also present in flat sheets, (2) the out-of-plane shear lag that is also present in an I-section bolted at the flanges only, and (3) the bending moment arising from the connection eccentricity with respect to the neutral axis. Each of the relevant factors is explicitly incorporated into the equation proposed in this paper for determining the net section tension capacity of a cold-formed steel channel brace bolted at the web. The proposed equation is demonstrated through laboratory tests on low-ductility channel braces having practical aspect ratios that were bolted onto flexible plates, to be more reliable than the code equations and those existing in the literature. [ABSTRACT FROM AUTHOR]

This paper presents the results of an experimental study on the critical buckling load and lateral bracing force of metal plate connected wood truss assemblies. Material property tests—including the modulus of elasticity of dimension lumber, flexural stiffness of plywood panels, and load-slip relationship of nail connection—and full-scale tests of individual trusses and truss assemblies were conducted. The critical buckling load and lateral bracing force were recorded. The continuous lateral bracing, the load sharing and distribution effects, and the residual deformation at the metal plate connections were studied for their influence on the system’s stability performance. The adequacy of the 2% rule of thumb, which is used by some design engineers for lateral bracing system design, was also discussed by comparing to the test results of the lateral bracing forces. The generated database can be used as input parameters and for verification for numerical analysis models and therefore contributes to the improvement of the design methods in the long term. [ABSTRACT FROM AUTHOR]

The global seismic response of 3- and 8-story eccentrically braced frames (EBFs), designed for western and eastern North American locations, is studied using nonlinear time history analysis. Analytical models were built in three computer programs. Similar maximum forces were obtained, but the inelastic deformation predictions at the element and global structural levels showed sensitivity to the modeling employed. This feature should be considered in seismic performance assessment or design. Current design methods failed to predict interstory drifts and plastic link rotations, but the study confirmed the strong correlation between the two parameters associated with rigid-plastic behavior. The influence of yielding and flexural buckling of frame members, other than the links on the global frame performance, was evaluated using the OpenSees model. It was confirmed that the flexural yielding of outer beams is acceptable for EBFs with short and intermediate links, if the combined flexural strength of the braces and beams is at least equal to the expected end-link moments and the braces can resist the associated axial force-bending moment demand. Inelastic response of braces and columns in such frames did not negatively impact the overall frame behavior. [ABSTRACT FROM AUTHOR]

A testing program has been carried out on typical bridging components and connections used in North American practice to provide bracing to cold-formed lipped cee-studs, in order to determine the in-plane and out-of-plane strength and stiffness of the bridging components and connections. Bridging systems tested included cold-formed bridging channels directly welded to the stud, bridging channels connected to the stud web through a welded connection to a clip angle, and bridging channels connected to the stud web through a screwed connection to a clip angle. Bridging connections were loaded axially (into the stud web) and laterally (parallel to the stud web). Separate analysis of the test results indicates that, within the range tested, conventional bridging used in current North American practice has adequate stiffness and strength to brace axially loaded and curtain wall steel studs. [ABSTRACT FROM AUTHOR]