Use of modal testing to identify damage on steel members

Abstract

There is a need to construct a structural monitoring system for assessment of current health condition of deteriorating structures and the prediction of their response under load. In this paper, basic experimental tests and numerical analysis are performed to investigate the feasibility of using modal testing techniques as a tool for structural health monitoring and damage detection. The objective of this study is to investigate the change of modal parameters due to imposed damage, and to verify the most sensitive modal parameters for identifying and locating the damage. Rectangular tudes, twelve feet in length, were tested for this purpose. They have either one or two spans and each of three cases has its own damage scenario. The modal parameters considered are modal frequency, displacement mode shape (DMS) and strain mode shape (SMS). The coordinate modal assurance criterion (CoMAC), and the modal vector error (MVE) are used to quantify the change of mode shape between the undamaged and damaged structures. The change of frequency can be measured rather precisely in this experimental test, but the location of damage could not be detected by use of DMS change with CoMAC. It is suggested that the DMS or preferably the SMS be used in collaboration with MVE as a more effective method of locating damage.