基于子结构的大型桥梁有限元模型修正方法

Substructure-Based Finite Element Model Updating of Long-Span Bridge

实际桥梁结构的整体有限元模型修正时自由度和单元数量较多,待修正参数多,有限元模型修正精度和效率低。为了提高有限元模型修正的效率,提出基于子结构的有限元模型修正方法。子结构方法是化整体分析为局部分析的方法,与直接修正大型桥梁有限元模型相比,子结构方法只需要计算每个子结构少量低阶模态,得到整体结构的特征解及特征解灵敏度,形成模型修正的目标方程和灵敏度矩阵,进而缩短模型修正时间。将基于子结构的模型修正方法用于怒江特大桥主桥(上承式钢桁拱桥)有限元模型修正,结果表明:修正后桥梁的前10阶频率与桥梁的模拟实测频率值相吻合,且模型修正时间仅为传统整体方法的56%。

When the global finite element model of a bridge is updated,various degrees of freedom and a large number of elements must be considered,the number of parameters needing to be updated is also large,and the updating accuracy and efficiency is usually not high.To improve the updating efficiency of finite element model,a method based on substructure is proposed.The substructuring method analyzes the structure in a piece-wise manner instead of analyzing the structure as a whole.Compared with directly updating the finite element model of a long-span bridge,the substructuring method only needs to calculate a small number of lower modes for each substructure to obtain the eigensolutions and eigensensitivity of the global structure,which are used to form objective function and sensitivity matrices in the process of model updating,respectively.Therefore,the computational time of model updating is reduced.The substructuring method was applied to update the finite element model of the main bridge of the Nujiang River Bridge(a deck-type steel truss arch bridge).The results show that the frequencies of the first 10 modes of the bridge after updating are consistent with the simulated field measurements,and the updating time is only 56%of the traditional global method.