Seismic Response of Braced Heavy Timber Frames with Riveted Connections

Abstract

Braced timber frames (BTFs) are one the most efficient lateral load–resisting systems to resist earthquake and high wind loads. Design guidelines for this system currently do not exist in Canadian wood design standards. Only seismic force modification factors for moderately ductile BTFs and limited-ductility frames are specified by the National Building Code of Canada. The code is vague about what types of connections can be used to achieve moderately ductile or limited ductility BTFs. This study investigated the seismic response of 30 BTFs using rivets designed with Rd=2.0 and Ro=1.5 by conducting pushover analysis following the coefficient evaluation method. The influence of key design parameters—i.e., configurations (single- versus multistory), number of stories, story heights, and aspect ratios of the tiers—on the stiffness, strength, and ductility of BTFs was discussed. The proposed seismic force modification factors for BTFs with riveted connections were evaluated preliminarily using the concept of collapse margin ratio (CMR). It was found that the system ductility of BTFs was much lower than that of connections. Single-story buildings possessed higher ductility, and CMR compared with multistory buildings. Single- and multistory BTFs with wider bays had higher strength ratio of demand to capacity and lower ductility and CMR. The building height limit of 20 m was conservative for multistory BTFS. The response of the investigated BTFs proved that Rd=2.0 and Ro=1.5 were appropriate for the seismic design of BTFs with riveted connections. Moreover, connections with ductility not less than that of riveted connections can be adopted by moderately ductile BTFs.