Large-Scale Dynamic Testing of Rocking Cross Laminated Timber Walls

Abstract

With the recent development of engineered wood products such as cross laminated timber (CLT), tall mass timber buildings are becoming a feasible and attractive alternative to using nonrenewable materials such as concrete and steel. Using CLT panels in a post-tensioned rocking wall system shows great potential for creating reliable, cost-effective, and rapidly constructible ductile seismic load resisting systems. The design of these systems are supplemented with replaceable steel U-shaped flexural plate energy dissipation devices (UFPs). This system has opened the door to creating seismic resilience systems that sustain minor damage during large earthquakes. With this in mind, the NHERI TallWood Project funded by the National Science Foundation, is developing a rocking cross laminated timber wall seismic force resisting system and design procedure for tall timber buildings that enables seismic resilience by meeting rigorous performance requirements. The system is designed to have no damage during a frequent hazard (such as a 50% probability of exceedance in 50 years), limits damage to the easily replaceable UFP devices in less frequent earthquakes (such as a 10% probability of exceedance in 50 years), and has more considerable damage that may require CLT repair and PT replacement in an even less frequent hazard (such as a 2% probability of exceedance in 50 years). Experiments conducted by the NHERI TallWood group tested a full-scale two-story mass timer building, with CLT post-tensioned rocking walls as the lateral system, on the world's largest outdoor shake table in San Diego, California at the NHERI@UCSD facility. Fourteen dynamic ground motion tests were conducted on the specimen and experimental results showed a ductile response with low levels of damage. In addition, the performance-based design procedure and performance objectives for the specimen matched well with the observed and instrumented response.