Seismic fragility estimation considering field inspection of reinforced concrete girder bridges

To study the seismic loss properties and performance of reinforced concrete (RC) girder bridge structures, the seismic damage experienced by RC girder bridges during the Wenchuan earthquake in China on May 12, 2008, was investigated and studied. The reconnaissance data of 1069 RC girder bridges in 21 highway sections (Sichuan, Gansu, and Shannxi Province, China) were analysed. The results indicated that the easily damaged parts included excessive displacement of the main girder or girder collapse, seriously damaged piers and abutments, excessive removal or failure of bearings, and seismic damage to the girder bridge caused by a secondary disaster. The bulk of the RC girder bridges were intact or slightly damaged, showing their excellent seismic performance. By improving the normal distribution function, an innovative nonlinear evaluation model (Gauss) was proposed to evaluate the fragility of RC girder bridges. The bridge sample data were counted and sorted, and the vulnerability levels of 1069 RC girder bridges were evaluated by using a novel model and a comprehensive macrointensity scale. An empirical fragility probability capability demand model (function, plane, surface, domain, curve, point cloud, and matrix) considering the damage rate, cumulative empirical probability, and average loss index parameters was established and verified. The results can be employed in future fragility research on this type of bridge.