Modal Identification of a Full-Scale Building Under Seismic Excitation Using the Fast Mode Identification Technique

Abstract

The sensors used in structural monitoring systems have becomemore affordable in the last few decades. The number of sensors used for monitoring is expected to grow, creating the need for new algorithms for online modal identification of structural systems. The fast mode identification (FMI) technique uses experimental data from ambient vibration tests to identify operational modal shapes at a fraction of the time used by traditional modal identification techniques. This paper discusses the mathematical formulation and experimental validation of the FMI technique on a full-scale building under earthquake excitation. The method consists of two steps: (1) the identification of natural frequencies and modal damping ratios using traditional techniques, and (2) the identification of operational mode shapes using the FMI technique. Dividing the process in two reduces the computational time required for modal identification. Experimental results show good agreement between the results of FMI and those of other widely used modal identification methods on a full-scale building submitted to seismic excitation. Furthermore, FMI shows a higher consistency on the identified mode coordinates and lower processing time than traditional methods. FMI is envisioned to be used on dense wireless intelligent sensor with limited processing capabilities and battery life.