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Topic

Numerical Study of the Structural Performance of Strong Wood Light-frame Shear Walls Under Large Lateral Loads

Department of Civil Engineering

Date & location

• Tuesday, November 19, 2024

• 2:00 P.M.

• Virtual Defence

Reviewers

Supervisory Committee

• Dr. Sardar Malek, Department of Civil Engineering, University of Victoria (Co-Supervisor)

• Dr. Min Sun, Department of Civil Engineering, UVic (Co-Supervisor) 

External Examiner

• Dr. Andre Barbosa, School of Civil and Construction Engineering, Oregon State University 

Chair of Oral Examination

• Dr. Marilou Gagnon, School of Nursing, UVic

   

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 findings of extensive numerical and analytical investigations focused on the behaviour of “strong” wood-frame walls subjected to large monotonic and cyclic loads, utilizing a 3D finite element (FE) model in ABAQUS software. 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. Using thicker OSB sheathing panels or materials with a higher modulus of elasticity (MOE) enhances energy dissipation while keeping the frame members and anchorage system within their elastic range. This suggests that optimizing the mechanical properties of sheathing panels can 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 of more resilient shear walls.