Deflection influence line - based bridge damage detection using high-resolution modal flexibility matrix with limited sensors

As a reliable, sensitive index for structural damage localization, influence lines (ILs) have attracted sufficient research attention in recent years. At present, most methods for obtaining ILs directly filter and separate sensors’ responses. Nonetheless, these methods usually demand a substantial amount of sensors to conduct global damage detection on long-span bridges, which limits their application in practical engineering. This paper proposes a new bridge damage identification method based on deflection influence line (DIL) with limited sensors. In this presented method, high-resolution mode shapes obtained by proper orthogonal decomposition (POD) are used to construct DILs of multiple bridge points to locate damages. First, the principal component matrix is calculated by applying POD to the bridge displacement response matrix under a moving load. Subsequently, the high-resolution mode shape is obtained by filtering out the dynamic information of the principal component matrix’s each column using a low-pass filter. Then, the obtained mode shapes are utilized to calculate the modal flexibility matrix. Finally, the DILs at multiple degrees of freedom (DOFs) of the bridge can be acquired based on the physical interpretation of the flexibility matrix. In addition, a damage index defined by DIL changes (DILCs) at multiple DOFs named DIL changes’ average is proposed, which has better stability than DILC at a single point. This method’s effectiveness is verified through numerical simulations and experimental verifications, and results indicate that this method can obtain DILs far more than the number of sensors and precisely identify bridge structural damages with only two sensors.