Post-earthquake strength assessment of a steel bridge considering material strength degradation

Abstract

After a catastrophic ground motion, the strength of a damaged steel bridge to resist both its self-weight and traffic loads usually needs to be re-evaluated. This aspect is especially true for bridges located in highway network intersections. However, in the current evaluation process, the strength of the deteriorated material is often underestimated, which may lead to the adoption of an inappropriate decision for the treatment of a damaged bridge. In this work, an accurate hysteretic model incorporating the strength degradation for structural steel is proposed based on experimental results. Furthermore, a case study on the post-earthquake strength of a deck-through type steel arch bridge was performed. The relationship between the prior seismic damage level and the remaining strength was investigated. The results indicate that the decreases in the material strength predicted by the hysteretic model are in good agreement with the experimental results. The stiffness of the bridge is unaffected by the seismic damage. The structure retains more than 90% of its original strength in most cases after the ground motions. However, the ductility of the structure decreases dramatically due to the prior seismic damage. Moreover, the remaining ductility of the damaged bridge decreases linearly with the preceding seismic intensities (PGA).