火致拉索破断斜拉桥安全分析

Safety Analysis of Bridge Under Fire-induced Cable Breakage

通过试验确定拉索着火后的温度场变化,建立了一座斜拉桥模型,采用单根或多根钢绞线逐渐破断的方式进行结构非线性动力分析,研究拉索着火破断后的结构安全性。引入动力放大系数(DAF)和需求能力比(DCR)分析主梁、主塔以及拉索的动力响应,研究了不同断索路径下的桥梁极限承载情况,计算了相邻拉索不同着火时间破断时桥梁结构动力响应,得出外索着火破断比内索着火破断更危险,整根拉索一次破断的模式不适合模拟斜拉桥拉索着火破断的情形。

An experiment is conducted to determine the temperature field of the fire-induced cable combustion. A cable-stayed bridge model is then employed to study its structural safety via nonlinear dynamic analysis when one or multi strands of the cable are gradually broken. The dynamic amplification factor （DAF） and demand capacity ratio （DCR） are introduced to attain the dynamic response of the main beam, main pylon and stayed cable. The impact of the breakage path, position, and combustion time of the cable on the ultimate load carrying capacity of the bridge are parametrically analyzed. It is concluded that the fire-induced inside cable breakage is danger than that induced by the outside cables. Moreover, the one-time breakage mode of the whole cable is not appropriate to simulate the process of the cable breakage-induced structural collapse.