Establishing the fundamental period of light-frame wood buildings on the basis of ambient vibration tests

Abstract

This research project deals with dynamic field testing of light-frame wood buildings with wood-based shear walls. The primary objective of the investigation is to evaluate the building code formula for estimating light-frame wood building’s fundamental period for seismic analysis, through intensive field testing and numerical modeling. The project also aims to propose an alternative simplified rational approach to seismic analysis of these structures. The paper presents ambient vibration testing results of light-frame wood buildings in Canada. The dynamic characteristics of the measured buildings, such as natural frequency, mode shapes, and equivalent structural damping were obtained from frequency domain analysis of ambient motion records. Using a simplified method of period estimation based on the Rayleigh approximation while using the building mass and replacing the stiffness of shear walls by their length showed reasonable fit when compared with the finite element model results and ambient vibration testing measured periods. A formula was developed based on the regression analysis of the tested buildings. The expression is a function of building height, floor area, and shear wall length and it was shown to provide a reasonably good fit with the measured results.