Seismic design and nonlinear response comparison of a hybrid timber building configured with BRB- and SMA-braced LVL frames

To achieve adequate performance during earthquakes, mass timber buildings are often combined with structural systems including other materials, resulting in seismic-resistant hybrid timber (SRHT) buildings. The state-of-the-art on the subject indicates that some of these hybrid systems have only aimed at increased stiffness and energy dissipation capability compared to timber-only structures, whilst others have also targeted a higher performance with minimal post-earthquake downtime for re-occupation. To compare both cases, this work presents the seismic design and nonlinear response evaluation of a SRHT building, 12-storeys tall, whose main seismic-resistant system included Laminated Veneer Lumber (LVL) frames braced with either Buckling Restrained Braces (BRB) or Shape Memory Alloy (SMA) devices-equipped steel braces. The design process showed that despite dividing the site response spectrum by a not so large reduction factor due to the existence of timber, practical and reasonable sizes of the structural members were able to satisfy the demand requirements. The results of the nonlinear dynamic analysis (NLDA) of the structures showed that both of them would respond within the accepted limits prescribed by international codes. The inclusion of the SMA devices upgraded the response of the hybrid building in terms of residual displacements and strains, but at the expense of having larger floor accelerations due to a reduced energy dissipation capability compared to the BRBs. It was concluded that both of the investigated systems are preliminary suitable for construction, and there is not a strict need for utilizing increased reduction factors. However, further research involving proper experimental testing is needed.