双屈服机制的外露式柱脚抗震性能分析

Seismic behavior of exposed-type column bases with double yield mechanism

外露式柱脚通常用于中高层钢结构建筑,它是上部主体结构与基础连接的节点,起着将上部荷载传递到基础的重要作用。当脚的破坏形式为锚栓破坏时,外露式柱脚的滞回曲线表现出捏缩行为和滑移行为,此时外露式柱脚的耗能相对较小。为了提高柱脚的耗能能力,本文提出了一种双屈服机制外露式柱脚构造措施,利用两层底板实现双屈服机制——外底板屈服机制和锚栓屈服机制:在循环加载的条件下,外底板进行耗能,内底板与锚栓共同作用,直至锚栓屈服。本文以外底板的厚度和锚栓的直径为参数,对循环加载下双屈服机制外露式柱脚的抗震性能进行了数值模拟研究。分析结果表明,该柱脚具有两种屈服机制,即外底板屈服机制和锚栓屈服机制,且随着外底板厚度的增加,该柱脚的耗能能力增大;随着锚栓直径的增加,该柱脚的承载力显著增大。

An exposed column base is commonly used in low-rise to medium-rise steel buildings.It is an important component to transfer axial forces,shear forces and moments from the entire structure into the foundations.The hysteresis curve of the exposed column base exhibits pinch and slip behaviors if it is designed as the anchor rods failure.Therefore,the energy dissipation of the exposed column base is relatively small.To improve the energy dissipation capacity,a double yield mechanism of the exposed column base is proposed.The double yield mechanism is achieved by using two layers of base plates.Two yield mechanism are the thinner base plate yield mechanism and anchor rods yield mechanism.Under the loading,the thinner base plate will yield and contribute to the energy dissipation.And the thicker base plate will work with the anchor rods and shows the anchor rods yield mechanism.Numerical study of the double yield mechanism of exposed column bases under cyclic loading are conducted.The parameters are the diameter of anchor rods and thickness of the thinner base plate.The analysis results indicate that the proposed column base showed two types of yield mechanism.The energy dissipation of the proposed column base is increased as the thickness of thinner plate increased.And the moment resistance of the proposed column base increased significantly as the diameter of the inner anchor rods increased.