Joint deterioration detection based on field‐identified lateral deflection influence lines for adjacent box girder bridges

As critical components that transmit internal forces laterally in multigirder bridges, joint degradation can destroy the cooperative working mechanism of a multigirder system and seriously reduce bridge bearing capacity. This research aims to reveal the joint damage effects on lateral internal force transmission and propose a joint damage detection and location method. A spring-jointed plate model is established to analyze the effects of joint damage, based on which the relationship between the shear forces in the joints and the shear stiffness of the joints can be obtained. Furthermore, a joint damage index is deduced based on the lateral deflection influence lines, and a bridge load testing method is proposed to obtain such influence lines. By using multiple influence lines to jointly solve the damage index, the joint damage in the lateral bridge direction can be accurately detected and located. In addition, by carrying out the damage detection process at several cross sections of the bridge, the joint damage position in the longitudinal bridge direction can also be determined. Finally, a numerical model of an adjacent box girder bridge is illustrated as an example to verify the effectiveness of the damage detection. It can be concluded that the proposed method can effectively identify and locate single or multiple joint damage locations under noise interference, and the joint damage degree can be quantitatively evaluated. This study can provide an effective method to identify the joint damage for adjacent box girder bridges with high accuracy and reliability.