Evaluation of safety and the collapse mechanism caused by sudden failure of members in truss bridges

构件突然失效产生的动应力放大对整体倒塌的进程有相当大的影响。因此，这种动力效应必须作为一个影响因素纳入常规的静力冗余度分析中。不同杆件的冲击系数计算值差别很大。然而，冗余分析中关键成员的影响系数几乎是一个恒定值，范围从1.4到1.8。为了在不进行动力响应分析的情况下近似预测杆件冲击系数的大小，提出了一种基于均方根模式组合法的简化方法。用该简化方法计算的杆件冲击系数精度中等。

The dynamic stress amplification resulting from a sudden failure of a member has a considerable influence on a progress to the overall collapse. Therefore, this dynamic effect must be included in the conventional static redundancy analysis as an impact factor. The calculated values of the impact factor vary widely from member to member. However, the impact factors for critical members in the redundancy analysis take almost a constant value that ranges from 1.4 to 1.8. In order to predict approximately the magnitude of the member impact factors without carrying out the dynamic response analysis, a simplified method based on the RMS mode combination method is proposed. The accuracy of the member impact factors calculated by this simplified method is moderate.