STRUCTURAL HEALTH ASSESSMENT VIA FINITE ELEMENT MODEL UPDATING

Abstract

Structural health assessment by tracking changes in the system parameters, identified using vibration-based methods have gained importance in recent years. The emphasis has been on detection and locating the damage in simple beam type structures or small framed structures tested in control environment using identified modal properties. The application of these methods to complex field structures requires strong vibration re sponse signals. For framed building structures, the vibration responses recorded at a few limited locations during strong earthquakes are often the only data available to identify systein parameters. The present study is attributed to issues related to structural health assessment of complex building frames designed as strong column-weak beam, with the aid of vibration based system identification and finite element model updating method, using limited number of responses recorded during strong earthquakes. The response of the structure at unmonitored degrees of freedom is estimated by interpolating recorded responses in time domain using piecewise cubic Hermite interpolation polynomial. System parameters in modal space (frequencies and mode shapes) are identified using frequency domain decomposition, empirical transfer function estimate and Gram-Schmidt orthog-oiialization. Changes in the frequencies and flexibility matrices are used to identify the presence of damages in the structure. Some attempts are made to locate the damage ini-tiating point. Several methods are examined to identify the damage location. It is found that for the current problem mode curvature method gives reasonably good estimate of damage locations. Sensitivity based finite element model updating procedures using Tikhonov regularization are used for quantifying the damage in the structure