平行钢丝吊索强度安全性分析与评估

Analysis and evaluation for the strength safety of the parallel sling wires

评估不同断丝数目时吊索的安全性能。在对某大跨径钢管混凝土拱桥三维有限元实体模型仿真分析的基础上,以拉索在恒载及汽车活载作用下的拉力安全系数为拉索失效判据,建立拉索失效功能函数。确定拉索失效功能函数中各参数的概率分布,采用Matlab计算软件生成各参数的随机样本,进而通过编程实现功能函数的计算机求解。采用Monte-Carlo法(蒙特卡洛法)评估吊索在不同损伤程度时的强度安全概率,计算各工况下吊索强度可靠性指标值并推导出吊索失效的临界断丝数。结果表明,吊索失效概率随断丝数的增加而急剧增大,吊索强度安全可靠性指标值随断丝数的增加近似呈线性衰减趋势。确定吊索失效的临界断丝数对吊索宏观检查和评估具有较大的工程实用价值。

The paper is inclined to present our research results on analyzing and determining the function state of the sling safety so as to evaluate its strength safety at the expense of some number of broken wires.Taking a certain bridge of the kind as the case study,we have built a 3-D finite-element model of a concrete-filled steel tube arch bridge and done a simulation analysis with it.In the combined way of the destruction load and the car regular load,the sling tension safety factor has been taken as the failure threshold.On the basis of analyzing the distributions of main parameters,we have generated some random samples by using a so-called Matlab software.Next,data of the random samples have been collected and converted into corresponding matrixes or vectors with the corresponding matrix state functions established.Based on the matrix function state analysis,we have worked out the calculating program through Matlab and accomplished the complex calculation of the matrix state functions with computers,which has made us possible to assess the sustainability of the broken sling damage by means of Monte-Carlo method.The curve of the reliability index-number of broken wires has thus been found with the formulas of polynomial regression and linear regression fitted through the least square fit.Furthermore,the critical number of broken wires has been defined as the reliability index to be zero.Through the linear regression formula,the critical number of broken wires has been deduced.The results of the evaluation indicate that the failure probability of cable may increase sharply with the increase of broken wires.But the decrease of the reliability index of the cable tension tends to follow an approximate linear relationship with the increase of the broken wires.Therefore,it is of great importance to calculate the critical number of broken wires,which can be used in inspecting and evaluating the sling safety macroscopically.