Full scale testing and development of wood-steel composite shear walls

Kyle Gere Conrad

Modern building designs often feature open floor plans and large shear wall openings, generally requiring pre-engineered solutions. In light frame timber construction, this can be difficult using wood frame shear walls which often require lengthy sections of wall to meet shear demands. This study explores a new prefabricated, pre-engineered shear wall with high base shear strengths at a 2:1 aspect ratio called the Wood-Steel Composite Shear Wall (WSCSW) with the goal of investigating the suitability of the system under cyclic lateral loading. The WSCSW utilizes a stiff timber boundary frame with a thin gauge steel web plate. Under lateral load, the web plate buckles in shear and resists the story shear through post-buckling tension field action. Existing literature was first reviewed, allowing for rapid prototyping of two different WSCSW designs by performing mechanics-based calculations. One design features an elastic boundary condition (Specimen 1), while the other features a plastic boundary condition (Specimen 2). Two WSCSWs were built at full scale and tested experimentally. Using experimental data and observations from testing, analyses were performed to describe the behavior of each WSCSW, assess the seismic and wind suitability by performing an equivalency study using ASTM Standard D7989, compare the unit shear strength of each WSCSW to that of wood frame shear walls, and derive a yield strength equation. Finite element models of both WSCSW specimens were developed to explore the yield progression of the web plate and the stress distributions in the boundary elements. It was found that the seismic unit shear of Specimen 1 and 2 were 6.3 and 4.6 times larger than those of code-approved wood frame shear walls. The wind unit shear of Specimen 1 and 2 were 4.5 and 3.3 times larger. The results of the equivalency analysis show that both WSCSW specimens meet overstrength and drift capability requirements to denote seismic equivalency, but do not meet ductility requirements for high seismic. However, both WSCSW specimens did exceed the allowable design drift of 2.5%. Specimen 2 also exceeded the maximum considered earthquake design drift of 3.75%.

Full scale testing and development of wood-steel composite shear walls

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