Damage detection of retrofitted crack re-initiation and growth

Abstract

This work presents a vibration-based damage-detection methodology that effectively captures crack re-initiation and growth of retrofitted connections simulating those existing on stop-hole retrofitted highway bridges. The proposed methodology calculates a damage indicator, based on limited frequency bands of the transmissibility function that have high coherence, as a metric for changes in the dynamic integrity of the structure. The methodology was tested using numerical simulation and laboratory experimentation of the connections before and after stop holes were implemented as stress relief measures. Throughout both the numerical and laboratory analyses, the results were used to successfully detect damage as a result of crack growth or formation of new cracks. Laboratory experimentation on retrofitted specimens showed the tendency for the crack to branch in different directions in lieu of re-initiating through the holes. It was observed that the damage indicator magnitude increased monotonically as damage increased in the specimen.