Characterization Of Wood Sheathed Cold Formed Steel Diaphragms PDF Download

"There exists a desire to better understand the in-plane response of cold-formed steel (CFS) framed diaphragms subjected to seismic loading. At present, the diaphragm design information available in the North American design standards (AISI S240, AISI S400) is not applicable in Canada and is of limited scope in the United States and Mexico. These design provisions are based largely on basic principles of engineering and the extrapolation of design methods used for wood diaphragms. Few full-scale tests have been performed to validate the accuracy of these design values and equations for real world application. Furthermore, the effect of non-structural components on the in-plane strength and stiffness of the diaphragm component has yet to be explored. In an effort to provide insight into the complex nature of the diaphragm structure and the influence of non-structural components, a research program was initiated in the Jamieson Structures Laboratory at McGill University focusing on the characterization of the behaviour of CFS framed - wood sheathed diaphragms under in-plane loading. A total of six 3.7m x 6.1m CFS diaphragm specimens with oriented strand board sheathing were tested following the cantilever test method. Three of these diaphragms focused on the effects of structural changes, while the remaining three were used to investigate the effects of incorporating non-structural elements in the construction. This thesis contains a detailed account of these six tests, including their design, construction and the overall results and observations. The tests focusing on structural changes, demonstrated that the orientation of the joists with respect to loading had little effect on the overall diaphragm response, strap blocking for panel edges was shown to be just as effective as full blocking and an upper threshold for shear strength and stiffness was reached by reducing the spacing of the perimeter fasteners. The tests of diaphragms built having non-structural elements demonstrated that both the addition of a single layer of gypsum panels to the underside of the diaphragm and a 19mm gypcrete topping poured on top of the wood sheathing had a significant strengthening and stiffening impact on the overall diaphragms response. Design predictions were calculated using the AISI S400 Standard for both deflection and shear strength. Meaningful comparisons were only realized for design deflection when the equation for shear walls was used with the values adjusted to remove inelastic behaviour, while no meaningful comparisons were realized for shear strength due to the limited information available within the S240 and S400 standards." --