基于柔度矩阵法的大跨斜拉桥主梁的损伤识别

Damage identification of main girders for long span cable-stayed bridge based on flexibility matrix

根据柔度矩阵的概念,构造出了一个损伤指标.采用有限元方法,对1座设定主梁不同位置发生损伤的大跨度预应力混凝土斜拉桥进行动力特性分析,提出了利用局部最优原则并根据指标曲线峰值点来对损伤进行判定的方法.研究表明,损伤指标可对主梁结构中不同位置设定的损伤进行识别判断;损伤指标随着结构损伤程度的增大而增大,当结构损伤程度不超过40%时,两者之间呈现出线性比例关系,而当结构中产生了很严重的损伤时,损伤指标随着损伤程度的增大而以幂指数的形式剧烈增大.损伤指标的识别精度与测点数目及测试误差有关,当测点数目减少一半时,损伤指标仍可识别出结构中设定的损伤,对模态参数做多次平均处理,有助于减少测试误差,提高损伤指标的识别精度.

A damage locating index was proposed based on the concept of flexibility matrix. The dynamic properties of a pre-stressed concrete cable-stayed bridge were analyzed by the finite element method. Various damage cases settled in different positions of a main girder were identified by the peak of the index curve according to the local optimum rule. The index can be used to identify the damage position and level. The index and the damage level have a linear proportional relationship when the damage level is less than 40%. When the damage in structures is very severe, the index will grow dramatically with a power exponent. The number and error of the measured points have influence to the precision of the index. The index can also be used to detect the damage when the number of the measured points is reduced to one half, and many times the average of modal shape parameters is helpful to increase the precision.