Ambient Vibration Testing of Canada’s Tallest Wood Frame Building

The objective of this research is to study the dynamic characteristics of the relatively new and increasingly popular class of tall wood frame buildings to better understand their natural mode frequencies and shapes. This study quantifies the dynamic characteristics of the tallest wood-frame building in Canada, the 18-storey Brock Commons building, located on the UBC campus in Vancouver, BC. Identification of the mode shapes and frequencies of the building contributes to improving the understanding of dynamic behaviour of tall wood buildings generally, especially to better model and predict their behaviour under seismic loading by parameterization of numerical models. In situ ambient vibration tests were conducted on the structure and the enhanced frequency domain decomposition technique was employed to carry out a complete operational modal analysis of the building. Translational modes in x- and y-directions, torsional, and rocking modes are identified, ranging in frequency from 0.940–9.232 Hz. Results show the fundamental period (1.064 s) is lower than the period predicted by the FE model (2.0 s), suggesting the building is less flexible than estimated. The identification of rocking modes similar to the natural frequency of the soil suggest that soil-structure interaction contributes to these modes, however a soil-specific study is required to further explore these effects.