Overview of a Project to Quantify Seismic Performance Factors for Cross Laminated Timber Structures in the United States

Cross-laminated Timber (CLT) has been extensively used in Europe and is now gaining momentum in North America; both Canada and more recently the U.S. Construction projects have shown that CLT can effectively be used as an alternative construction material in mid-rise structures and has significant potential in commercial and industrial buildings. In the United States, the CLT system is not currently recognized in seismic design codes and therefore a seismic design can only be performed through alternative methods specified in the codes. The FEMA P695 report published in 2009 presents a methodology to determine seismic performance factors namely the response modification factor, overstrength factor, and deflection amplification factor for a proposed seismic resisting system. The methodology consists of a number of steps to characterize system behavior and evaluate its performance under seismic loading. The additional benefit of the methodology is that it considers variability in ground motions and uncertainties in tests, design, and modeling. This paper presents an overview of the P695 methodology and more specifically the approach adopted to apply the methodology to Cross Laminated Timber (cross lam) systems in the United States. The type of tests and testing configurations conducted as part of this study and development of the CLT archetypes are discussed. Nonlinear models used to simulate CLT behavior at the connection, wall, and system levels are presented and the procedure to determine collapse margin ratio is explained.