Health monitoring of connections in steel frames using wavelet transform

The behavior of steel frames during earthquakes depends on the performance of their joints. In this study, the event of damages in beam-to-column connections of steel frames subjected to an earthquake ground motion is detected, which is related to the numbers of spikes in wavelet results. The proposed method is based on the detection of abrupt changes in seismic vibration responses by the analysis of velocity responses using wavelet analysis. In order to model damage at the joints, beam-to-column connections are considered to be semi-rigid and damage is considered based on the end-fixity factors. In the proposed method, velocity responses for the different damage cases under Kocaeli (1999) earthquake was analyzed using wavelet transform. The peak values of the details of the response can be expressed the time of damage occurrence in the beam-to-column connections. To illustrate the effectiveness of the proposed method, a five story and ten story steel frames have been used. The results indicate that the proposed method has been able to identify the damage occurrence in the connections with high accuracy.