Seismic performance of braced timber frames

Braced timber frames are efficient lateral load resistance systems in buildings where large open spaces are required, and the more commonly used timber shear wall systems cannot be utilized. Braced timber frames allow for flexibility in the design and use the wood in its strongest direction - parallel to grain in tension or compression. For application in high-risk earthquake zones, however, the ductility of the system is a concern, since energy absorption is typically limited to the connection region. This study focused on seismic behaviour of braced timber frames with particular emphasis on investigating the influence of different connection details on the overall stiffness, strength and seismic energy absorption capacity of the frame. Monotonic tension and cyclic quasi-static tests were conducted on a variety of connections typically used in braced timber frames, utilizing different diameter bolts and high strength glulam rivets with steel side plates. Shake table tests were subsequently conducted on a selected number of single storey braced frames with some of the connections previously tested and on a two storey braced timber frame model with riveted connections. The experimental results from quasi-static tests and shake table tests were used to establish and verify non-linear analytical models representing the load-deformation behaviour of different connections. These hysteresis curves were then introduced in analytical braced frame models. These models were used in a number of non-linear static and dynamic analyses to determine the response of braced frames to the input of five different records from previous earthquakes. From these analyses it was possible to determine the influence of different connection details on the seismic response of the selected types of braced timber frames. Based on the results from the analytical part of the study, an estimate was made on the appropriate force modification factors (R-factors) for earthquake resistant design of braced timber frames, as used in the National Building Code of Canada. Finally, some design and construction recommendations are discussed to inform the reader of the details required to obtain an adequate seismic performance. Possible ways of improving the seismic behaviour of braced timber frames are presented as well.Applied Science, Faculty ofCivil Engineering, Department ofGraduat