Method of Modal Identification of Torsionally-Coupled Buildings Using Earthquake Responses

Abstract eng:
A vibration monitoring procedure based on recorded and reconstructed response has been presented in the paper. The method allows modal identification using recorded responses from only few floor levels, that are selected based on minimax error criterion. The vibration responses at non-instrumented floor levels are estimated using spline-based reconstruction. The complete sets of recorded and reconstructed signals are used together in the parameter identification algorithms to identify the modal model of the structure. The state space model of the structure is obtained using Eigen Realization Algorithm to cross correlation functions derived from the complete set of responses. The modal properties viz., natural frequencies, modal damping ratios and complete mode shapes are estimated from state space matrices. A numerical verification has been carried out on a multi-story building subjected to earthquake base excitations. The numerical verifications show that there is good agreement between actual and reconstructed floor responses. The identified modal properties have been compared to their actual values using correlation techniques. The correlation results show good accuracy in the identified frequencies and mode shapes for first few fundamental modes. The procedure can be effectively applied to condition assessment and structural health monitoring problems since vibration records are required at only a few floor levels, and the fundamental frequencies and mode shapes are identified with required accuracy.

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