余震地区桥梁施工过程易损性分析

THE VULNERABILITY ANALYSIS OF BRIDGE CONSTRUCTION IN AFTERSHOCK AREA

震后灾区重建工作中,桥梁等关键基础设施应迅速修复或重建,以满足灾区交通需求。施工过程中,桥梁整体结构体系尚未形成,且短期内余震频发,将严重威胁着结构安全。通过余震序列早期阶段的统计结果,回归出余震发生概率模型,基于概率的地震危险性分析理论(PSHA),提出了桥梁施工过程中易损性指标与考虑施工过程的易损性模型。以汶川地震为例,对一座山区高墩施工整个过程的易损性展开分析,结果表明:余震地区桥梁施工易产生开裂损伤破坏,影响结构耐久性,有必要对强震过后灾区桥梁施工阶段的地震损害风险做专门的评估。

During post-earthquake reconstruction, bridges and other key infrastructures should be quickly repaired or reconstructed for travel demand. During construction, integrated structural system of a bridge has not formed yet and aftershocks occurred at a high frequency in a short time, which would threaten the security of the structures. By the statistical results of aftershock occurrence in the early stage after the main shock, the current study regressed the probabilistic model of aftershock occurrence, which is based on the Probabilistic Seismic Hazard Analysis （PSHA）, and proposed a fragility index in the process of the bridge construction and considered the calculation model of fragility in construction process. Take Wenchuan earthquake as an example. By analyzing the fragility of high piers in a mountainous area during the whole construction, it is shown that cracking damage easily occurs during the bridge construction in aftershock area and can affect the durability of the structure. Therefore, it is necessary to make a special assessment on the risk of earthquake damage to bridges under construction after strong shocks.