Shake-table experimental testing and performance of topped and untopped cross-laminated timber diaphragms

Abstract

This paper presents the behavior of floor diaphragms of a shake-table experiment of a full-scale two-story mass-timber building structure. The structure consists of glued-laminated timber beams and columns, while floors and walls were designed and built making use of cross-laminated timber panels. Two different floor systems were designed, where the roof consists of a topped CLT-concrete composite system, while the floor level consists of un-topped CLT panels connected with plywood single surface splines. The CLT floor systems were designed to remain essentially elastic over the whole series of shake-table tests, which included testing of three lateral force resisting systems tested at three different seismic intensity levels (service level, design basis, and maximum considered earthquake) for a total of 34 shake-table earthquake tests. Results from the testing indicate that CLT diaphragms designed to remain essentially elastic based on basic principles of structural mechanics and existing test data can achieve desired seismic performance objectives. In addition, sources of over-strength in certain elements of the diaphragm need to be explicitly considered for a holistic diaphragm design.