Modal Identification Using SMIT

Abstract

The objective of this paper is to introduce a Structural Modal Identification Toolsuite (SMIT) for MATLAB that has been recently developed to facilitate system identification of structural systems. SMIT is an integrated toolbox, supporting a user-friendly Graphical User Interface (GUI) for modal identification. In this paper, the results of several system identification methods are compared in terms of accuracy and efficiency. The toolbox is capable of performing several common system identification methods with a standardized process, which is composed of input, eigenvalue estimation, and post processing procedures. The toolbox can present the estimated modal parameters graphically, and conveniently store and recall the identification results. The implemented identification methods consist of several classes of system identification algorithms, including Eigensystem Realization Algorithm (ERA), Auto-Regressive Moving-Average method with eXogenous terms (ARMAX), and Stochastic Subspace Identification (SSI). The performance of SMIT was verified by identifying the modal parameters of Northampton Steel Bridge (NSB), using five identification algorithms. A set of ambient acceleration responses was collected using a Wireless Sensor Network (WSN), and a subset of the sensing nodes was selected to identify vertical and torsional modes of NSB. The comparison of identification results to examine the accuracy and efficiency of each method supports that the SMIT is applicable to identify civil infrastructures effectively.