水平双向地震作用下钢桥墩损伤区域长度研究

钢板局部失稳是典型的钢桥墩地震破坏形式之一，因此在进行结构地震反应分析时需要考虑钢板局部变形对计算结果的影响。为了研究钢桥墩结构的地震损伤特征并为建立合理的杆系-板壳混合单元模型提供依据，以矩形截面钢桥墩为对象，采用板壳有限元模型和修正双曲面滞回本构模型分析了结构在水平双向反复荷载作用下的破坏过程，讨论了加载路径对桥墩承载力、延性以及极限状态下局部变形特性的影响；通过结构参数分析拟合了钢桥墩地震损伤区域长度预测公式；通过全板壳单元模型和杆系-板壳混合单元模型的桥墩弹塑性地震反应分析结果对比，验证了损伤区域长度预测公式的适用性。结果表明：钢桥墩在单方向上的承载能力和延性特性与荷载作用路径有关，沿正方形加载时结构的延性最小，沿斜方向加载时结构的承载力最小；荷载作用路径对钢桥墩极限状态下的损伤区域长度影响不明显；矩形截面钢桥墩地震损伤区域长度主要与截面宽度及横隔板间距有关，根据这2个参数建立的钢桥墩地震损伤域区域长度预测公式能够正确反映结构在水平双向地震作用下发生局部失稳的范围。该公式可为钢桥墩地震损伤范围预测以及合理混合单元模型的建立提供参考依据，但预测结果偏于保守，精度仍有待于进一步提高。

Lengths of Damaged Zones of Steel Piers Under Bidirectional Horizontal Earthquake Components

Local instability of steel plates is one of typical forms of seismic failures of steel piers. Therefore, the influence of local deformations of steel plates on the calculation results needs to be considered in the structural seismic response analysis. In order to study the seismic damage characteristics of steel piers and provide a basis for establishing a reasonable beam-shell hybrid model, a rectangular-section steel pier was considered as the object, and the structural failure process under bidirectional horizontal cyclic loads was analyzed using shell finite element (FE) model and the modified two-surface hysteretic constitutive model. The influence of loading path on bearing capacity, ductility, and local deformation characteristics in the ultimate state of structures was discussed. Structural parameter analysis was conducted to fit the prediction formula for lengths of seismic damage zones of steel piers. The elastoplastic seismic response analysis results of shell element model and beam-shell hybrid element model were compared, and the applicability of the prediction formula for lengths of seismic damage zones was verified. The results show that the bearing capacities and ductilities of steel piers in one direction are related to the loading path. The ductility is lowest under the square path, and the bearing capacity is lowest under the oblique direction. The influence of loading path on lengths of damaged zones of steel piers is not obvious. Lengths of the seismic damaged zones of steel piers are mainly related to section widths and spacings between two diaphragms. The prediction formula for lengths of seismic damaged zones of steel piers based on these two parameters can correctly reflect the range of local instability of the structures under bidirectional horizontal earthquake action. This formula can provide a reference for predicting seismic damage zones of steel piers and for establishing reasonable hybrid element models; however, the prediction results are rather conservative, and the precision needs to be further improved.