现有桥梁的可靠性分析

为了准确地把握现有城市公路桥梁的损伤程度,将桥梁评定单元划分为下部结构、支座、上部结构及桥面系等4个组合项目,每个项目包含若干个子项,从而形成子项、项目和单元3个层次,每个层次划分为4个等级.在各个层次上,直接对可靠性进行评级.组合项目的等级评定中引用了故障树的逻辑原理来表示构件可靠性和结构可靠性之间的关系,采用了传力树评级法.同时,把工程模糊论方法应用到结构可靠性分析中,按危险点所占比重划分桥梁组成部分的评定等级,由各组成部分的危险构件百分数可得到构件对各等级的隶属度,从而构成桥梁等级的评判矩阵.通过模糊矩阵的复合运算,对桥梁的危险性进行鉴定,为维护与加固的合理决策提供依据.

Reliability Assessment for Existing Bridges

In order to improve the security performance of existing bridges, the reliability analysis and health detection for them are made. Bridge, as the evaluation unit, is divided into four combination items of underground part, support, top part and bridge surface. Each item consists of several subitems, and a system is built of three levels of subitem, item and unit, each of which is partitioned into four grades. In the grade evaluation of the combination items, the logic principle of the fault tree is introduced to build the relationship between the components reliability and structure reliability, and at the same fime the method of transmit tree evaluation is adopted. Besides, engineering fuzzy theory is used to analyze structure reliability, in which the evaluation grades of the parts of a bridge is decided by the percentage of the dangerous points, and the constitute attachment to the every grade is determined by the percentage of the dangerous constitutes of every part and finally the judgment matrix of bridge grade is built By the compound operation of the fuzzy matrix, the danger of the bridge can be judged and the evidence is provided for the reasonable decision of its maintenance and reinforcement.