Dynamic performance assessment of a multi-story timber building via long-term seismic monitoring and model updating

The Nelson Marlborough Institute of Technology Arts building is the world’s first commercial implementation of a post tensioned Laminated Veneer Lumber (LVL) shear wall system based on EXPAN technology. In order to understand the response of the building in a serviceability level seismic event, System Identification using dynamic monitoring data, Finite Element (FE) modelling, model updating and time history analysis was performed. Several modal frequencies, damping ratios and mode shapes were identified form the seismic response records. Model updating estimated a 16% increase in the stiffness of LVL structural elements, an approximate 90% decrease in concrete, and nearly nil contribution of cladding to stiffness. An estimation of the serviceability response was made based on a single degree of freedom system time history analysis. It was concluded the NMIT building performs well under serviceability seismic loading. The maximum deflection of a 1/25 year event was estimated to be 8mm.