Modal investigation of the Usibelli Building using spectral and dynamic analysis

Abstract

The purpose of this master’s project is to complete a modal analysis of the Joseph E. Usibelli Engineering Learning and Innovation Building. The modal analysis was conducted in two ways: by completing a spectral analysis using data collected from 7 seismometers and using a computer model of the building’s structural Lateral Force Resisting System. Power spectrum density plots were generated using a Fast Fourier transform routine within MATLAB to identify the natural periods of the building. A building model was created in RISA-3D using construction plan sets to apply a dynamic load and then to find the natural periods of the building. Accurate results from a spectral analysis require multiple earthquakes that have a seismic input at low frequencies. The results in this report found a maximum of two fundamental modes using spectral analysis, which matched well with eigenvalues from the RISA-3D model. The advantage of the spectral analysis is that it is a direct representation of what is going on inside the building. In contrast, the dynamic analysis is used to benchmark the results.