Performance of mid-ply wood shear walls with openings

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Driven by the growing demand on strong lateral load resisting systems in regions susceptible to severe earthquakes or strong winds, the mid-ply shear wall was first developed in the 1990s in Canada. Testing has shown that mid-ply walls possess approximately two to three times the lateral capacity of conventional wood shear walls. Design provision for mid-ply shear wall systems was implemented first time in Canadian timber design standard CSA O86 in 2014. As home owners increasingly favour an open space concept and large glass façades with few structural shear walls and large openings, the strong mid-ply shear wall has further attracted the attention of designers in recent years. This is a global trend that is happening in North America as well as overseas countries that import Canadian wood products for construction. The increase of allowable building height for wood construction from low-rise (upto 4 storesy) to mid-rise (6-storey) in recent years has led to increased interest in this strong wood shear wall to address the higher design loads, especially in the lower storey of mid-rise buildings. In this context, a key question has been raised recently regarding the effects of openings, which are often required for windows and doors, on stiffness and strength properties of mid-ply walls. This project is intended to address this issue. The specific objectives are to develop framing details around an opening in mid-ply walls to minimize the impact of the opening on the strength and stiffness of the assembly and to evaluate the influence of relative size and location of an opening on the strength and stiffness of a mid-ply wall. This research will lead to design guidelines to address mid-ply walls with openings as well as construction detailing around openings that would allow segments of mid-ply walls with openings to retain an acceptable level of stiffness and strength. The success of the proposed research will help to increase the use of Canadian lumber and wood-based panels domestically as well as in overseas markets.