This study aims to investigate the effect of soil-structure interaction (SSI) on the seismic response of a medium-span old concrete arch bridge in Iran's railway network, through incremental dynamic analysis (IDA). To this end, the finite element model of the bridge was developed and its dynamic properties were calibrated based on experimental results. The effect of soil-foundation flexibility was taken into consideration in the computational model. Results from analyses were summarized in IDA curves and the effect of SSI was assessed through the probabilistic framework. To this end, the failure state of bridges was evaluated and a comparison was made between the rigid and flexible base models. The mean annual frequency of exceeding the failure state of the rigid-base bridge was also compared with flexible-base models to investigate the effect of SSI on the return period of failure state of the bridge. Furthermore, the SSI effects were assessed on the confidence level of bridge safety. Results show that ignoring the SSI effect leads to an overestimation of bridge capacity as well as the confidence level of satisfying the safety state. Similarly, the return period of bridge failure increases when a rigid-base model is employed.

这项研究旨在通过增量动力分析（IDA）研究土-结构相互作用（SSI）对伊朗铁路网络中跨度老混凝土拱桥地震响应的影响。为此，开发了桥梁的有限元模型，并根据实验结果对其动力特性进行了校准。计算模型考虑了地基柔性的影响。分析结果总结在IDA曲线中，并通过概率框架评估了SSI的效果。为此，评估了桥梁的破坏状态，并对刚性和柔性基础模型进行了比较。还将超过刚性基础桥梁破坏状态的年平均频率与柔性基础模型进行比较，以研究SSI对桥梁故障状态恢复期的影响。此外，评估了SSI对桥梁安全性置信度的影响。结果表明，忽略SSI效应会导致高估桥梁容量以及满足安全状态的置信度。类似地，当采用刚性基础模型时，桥梁破坏的恢复期会增加。