沿海氯盐环境下地铁车站结构地震响应规律

Seismic response patterns of subway station structures in coastal chloride environments

摘要:

地铁车站结构抗震分析中,通常只对完好结构进行地震响应规律分析,然而,沿海城市地铁车站结构埋置于地下,易遭受氯离子侵蚀,导致材料性能退化。为此,针对沿海氯盐环境下不同锈蚀程度的地铁车站结构,建立相应的非线性土-结构相互作用有限元模型。采用整体式静力推覆分析,研究氯离子侵蚀对土-结构柔度比的影响,并基于非线性时程分析,研究氯离子侵蚀下地铁车站结构的地震响应规律。数值模拟结果表明:相对完好状态,10%和20%锈蚀率的车站结构土-结构柔度比分别下降6%和18%,然而,由于地下结构受到周围土体的约束,在相同地震作用下,底层中柱的最大层间位移角没有显著变化；底层中柱作为抗震薄弱环节,钢筋锈蚀造成中柱变形能力及承载能力的下降,导致地铁车站结构的安全系数下降10%和20%左右；锈蚀后结构中柱最大层间位移角增幅与场地响应有关,低频成分丰富的地震作用下,土体将产生大的剪切变形,使得中柱纤维截面中钢筋承担更多的剪力,此时钢筋锈蚀将对中柱层间位移角产生较大影响。

Abstract:

Previous seismic analysis of subway stations typically focused on analyzing the seismic response of intact structures. However, subway station structures are buried underground and are susceptible to chloride ion erosion. This can result in the degradation of material performance. This paper aims to establish nonlinear soil-structure interaction finite element models for subway station structures with different degrees of corrosion under chloride environments at coastal areas. The static pushover analysis method was utilized to investigate the influence of chloride ion erosion on the soil-structure flexibility ratio. Furthermore, based on nonlinear time history analysis, the seismic response of subway station structure in coastal chloride environments was analyzed. The numerical simulation results indicate that compared to the intact state, the soil-structure flexibility ratio of the structures with 10% and 20% corrosion rates decreases by 6% and 18%, respectively. However, due to the confinement of the surrounding soil, the maximum inter-story drift angle of the lower-level columns does not exhibit significant changes under the same motion. As the vulnerable component in seismic resistance, the corrosion of reinforcement in the lower-level columns leads to a decrease in their deformation capacity and load-bearing capacity. This results in a reduction of the safety factor of subway station structures by approximately 10% and 20%. The increase in the maximum inter-story drift angle of corroded columns is influenced by the site response. Under the motion with a rich low-frequency component, the significant shear deformations of the soil lead to a situation where the reinforcement in the fiber section of the columns bears more axial force. At this point, the corrosion of reinforcement will have a significant impact on the inter-story drift angle of the columns.