Overturning-Collapse Modeling and Safety Assessment for Bridges Supported by Single-Column Piers

Abstract

Overturning collapse has been regarded as one of the most critical failure modes for single-column-pier bridges in current practices. To reveal the entire overturning process, a meticulous three-dimensional (3D) simulation of bridges with superstructures, bearings, and piers, considering geometric and material nonlinearities, was first established. Multiple load patterns were applied, including the practical eccentric truckloads that lead to overturning incidents and the conventional checking loads that are defined in the bridge design specifications. Second, four sequential limit stages of the overturning process were defined to precisely describe the structural behaviors under different mechanical conditions before the final collapse. A safety indicator was further proposed to quantify the possibility of overturning with respect to different limit stages. Using such a safety indicator in a case study, the ability of bridges to resist overturning was assessed and compared to results from the specifications and field observations. By doing this, the drawbacks of specifications in checking the safety of single-column-pier bridges were demonstrated. A parametric study was finally conducted to investigate the influence of different single-column-pier bridge arrangements on the overturning behaviors. It can be concluded that the specification-based methods greatly overrate the safety level of single-column-pier bridges, whereas the safety indicator provides more reasonable results as well as multiple-sublevel safety warnings up to the final collapse. Additional findings and suggestions for a better design or maintenance of single-column-pier bridges in curved-girder cases were also discussed.