Numerical study of the structural performance of strong wood light-frame shear walls under large lateral loads
Date
2024
Authors
Ghazinader, Dina
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Abstract
The motivation for this study comes from the increasing demand for safe, affordable wood-frame buildings in Canada over the past decade, primarily due to their low cost, high ductility, and ease of construction. In such buildings, wood-frame shear walls are commonly utilized as the main lateral load-resisting system to resist seismic loads. Wood-frame shear walls are typically comprised of timber framing members, sheathing panels such as plywood or oriented strand board (OSB), and fasteners like nails and bolts. The best performance of such walls is achieved when most of the energy is dissipated through shear deformation in the sheathing-to-framing connectors (i.e. nails) while the framing and anchorage systems remain in their elastic regime. This study presents the results of extensive numerical and analytical investigations into the behavior of "strong" wood-frame walls subjected to large monotonic and cyclic loads. A detailed 3D finite element (FE) model in ABAQUS software was employed for an in-depth analysis of shear wall components and to examine the impact of various parameters on their performance. The accuracy of the FE model for both the nail connectors and the wall assembly is validated by comparing its results with experimental data from the literature. Further analyses showed that the Canadian Standards Association (CSA), and the Special Design Provisions for Wind and Seismic (SDPWS) guidelines slightly overestimate the initial wall stiffness, with the discrepancy increasing at larger displacements. The numerical analyses conducted on strong shear walls with different hold-down systems show that discrete hold-down system can overstress the end studs, increasing the risk of wood crushing and brittle failure in the framing members.
In contrast, continuous steel rods maintain stresses within safe limits and shift the failure mode (nail yielding) from the end studs to the center of the wall, thereby enhancing the overall structural performance. The numerical results further indicate that, although the diameter of continuous rod hold-downs does not significantly affect the wall’s strength, it plays a critical role in delaying yielding in the anchorage system, thereby improving the overall wall performance and energy dissipation under lateral loads. Numerical results also show that thicker OSB sheathing panels or materials with a higher modulus of elasticity (MOE) improves energy dissipation while ensuring the frame members and anchorage system remain within their elastic range. Thicker panels help prevent edge tear-out and nail head pull-through by reducing the crushing of wood strands in the OSB, allowing the nails to deform more before ultimately withdrawing. This suggests that optimizing the mechanical properties of sheathing panels may improve shear wall performance and energy dissipation while minimizing the need for additional nails, providing a balanced approach to enhancing both strength and ductility in the design leading to more resilient shear walls under strong earthquakes.
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Keywords
Wood light-frame shear walls, Numerical study, Structural performance