Mass timber products, such as the glulam or cross laminated timber (CLT), are less frequently used construction materials at present for mid-rise and high-rise buildings. The feasibility and possible advantages of applying timber materials for constructing mid- and high-rise buildings are under investigation. One of the issues that needs to be addressed for the use of heavy timber materials is the safety of such constructions under seismic excitations. To address this issue, the nonlinear inelastic seismic responses and capacity curves of a wood buildings must be assessed. For this, the 10-, 15- and 20-storey buildings are designed using heavy timber structural members considering the requirements stipulated in applicable Canadian design codes and standards. When considering the buildings under unidirectional ground motion, the structural capacity curves along the structural axes in the horizontal plane are identified using well accepted approaches such as the incremental dynamic analysis (IDA) and nonlinear static pushover analysis (NSPA). The capacity curve is used as the basis to develop equivalent nonlinear inelastic single-degree-of-freedom (SDOF) system. The equivalent SDOF system is then employed for the structural reliability. The results indicate that the estimated reliabilities of the designed timber buildings are similar to those of steel frame structures designed according to Canadian practice. To consider the effect of the bidirectional ground motions on the building responses and their seismic reliability, a procedure is proposed in develop the capacity surface based on the results from the IDA and NSPA. Also, a procedure is proposed to establish equivalent nonlinear inelastic two-degree-of-freedom (2DOF) system based on the capacity surface. The use of the equivalent 2DOF system largely simplifies the reliability analysis of the buildings under bidirectional ground motions. The analysis results indicate that the failure probabilities under bidirectional ground motions are about 3 to 8 times greater than those obtained under unidirectional ground motions. Therefore, the consideration of bidirectional ground motions in assessing the reliability of building under seismic ground motions can be important for seismic risk modeling and emergency preparedness.
