基于高斯过程模型的桥梁时变系统地震易损性分析

Seismic fragility analysis of the time-varying system of a bridge with a Gaussian process model

摘要:

桥梁在长期服役过程中面临的氯离子侵蚀作用会导致材料性能退化,进而影响桥梁结构的抗震性能。准确评估服役桥梁的抗震性能可以有效保障和提高桥梁结构的安全性,因此开展考虑时变效应的桥梁地震易损性分析非常必要。考虑到地震易损性分析涉及大量的动力时程分析,计算效率很低,故采用高斯过程模型取代耗时的动力时程分析,旨在提高地震易损性分析效率。以一座三跨连续梁桥为例,探究氯离子侵蚀作用下桥墩材料性能的退化规律,建立纵筋、箍筋以及保护层和核心混凝土材料性能退化时变曲线;基于高斯过程模型和联合概率地震需求模型,建立桥梁系统在不同服役年限下的易损性曲线和曲面。结果表明:(1)氯离子侵蚀作用明显降低了桥墩钢筋混凝土材料的强度；(2)氯离子侵蚀作用明显提高了高等级损伤的桥梁地震易损性,结构更容易发生高等级损伤。

Abstract:

Chloride ion erosion in bridges in long-term service leads to the degradation of material properties and affects the seismic performance of bridge structures. Accurately evaluating the seismic performance of bridges in service can effectively guarantee and improve the safety of bridge structures. Therefore, seismic fragility analysis considering a time-varying effect is essential. In this study, the time-varying seismic fragility analysis of bridges was carried out. The degradation of material properties caused by chloride ion erosion on the seismic performance of the bridge was considered. Given that seismic fragility analysis involves comprehensive dynamic time-history analysis, the calculation efficiency is low. Thus, the Gaussian process model was used to replace the time-consuming dynamic time-history analysis to improve the efficiency of the analysis. The degradation law of the pier material properties under the action of chloride ion erosion was explored in a three-span continuous beam bridge. Then, the degradation time-varying curves of the longitudinal reinforcement, stirrup, protective layer concrete, and core concrete were established. Based on the Gaussian process and probabilistic seismic demand models, the fragility curves and surfaces of bridge systems with different service years were established. Results show that (1) the strength of the reinforced concrete materials of piers is substantially reduced by chloride ion erosion, and (2) chloride ion erosion obviously increases the seismic fragility of the bridge with high-level damage, and the structure is more prone to high-level damage.