Mass Timber Frames with Timber Buckling Restrained Braces

Abstract

A timber lateral force resisting system (LFRS) with timber buckling-restrained braces (TBRB) is proposed to improve the seismic performance of timber buildings. Using a similar design approach for conventional buckling-restrained braced frames (BRBF) and established design methods for timber connections, a timber buckling-restrained braced frame (TBRBF) was designed and tested under a series of quasi-static cyclic loading protocols. During the tests, the level of axial load applied to the column was varied to simulate gravity loads. Additionally, some of the tests included an out-of-plane displacement imposed on the upper east connection of the frame. The results of these tests show that the TBRBF is able to achieve 1.5 times the requirement for the cumulative inelastic displacement (CID) set by AISC for conventional BRBs. The TBRBFs were able to reach approximately 3.0% story drift before TBRB failure due to splitting of the casing. To improve the performance of the TBRB, some of the tests included a TBRB which was enhanced with carbon fiber wrap at the two ends of the casing. This enhancement increased the story drift capacity to 4.5% and changed the failure mode of the TBRB from splitting of the MPP casing along its length to fracture of the steel core. Finally, the bare frame was tested on its own to provide improved understanding of the performance of the subassembly. The results of the entire experimental program suggest that the TBRBF behaves as a dual system and is well-suited as a LFRS for timber buildings in seismic regions.

Citation

Williamson, E.; Pantelides, C.; Blomgren, H.-E.; Rammer, D. 2024. Mass Timber Frames with Timber Buckling Restrained Braces. In: Proceedings of the 18th World Conference on Earthquake Engineering. Milan, Italy. June 30-July 5, 2024. 10 p. https://www.wcee2024.it.