基于模态测试的宽幅钢箱梁桥有限元模型建立、修正与分析

Finite element modelling,modification and analysis for wide steel box-girder bridges,based on modal tests

建立精确的宽幅钢箱梁桥有限元模型对此类结构的动力性能评估与结构设计有着重要的意义。建立了宽幅钢箱梁桥精细三维有限元模型,对宽幅钢箱梁桥不同施工阶段开展基于环境激励作用下的模态测试,采用随机子空间法与峰值拾取法识别桥梁的前十二阶模态,基于模态识别结果采用响应面法对桥梁有限元模型进行修正,详细分析了桥梁铺装层、邻跨等效质量对桥梁模态的影响。分析结果表明:建立的有限元模型具有较高的精度;铺装层会显著降低桥梁各阶自振频率,邻跨等效质量对桥梁的横向与扭转频率有显著的影响。

An accurate finite element model for wide steel box-girder bridges is very important for the evaluation of structural dynamic performance and the structural design. A sophisticated finite element model was presented for a certain wide steel box-girder bridge. Modal tests in various stages of construction were carried out based on the field ambient vibration excitation. The stochastic subspace identification and peak picking of the average normalized power spectral densities were used to identify the bridge ＇s dynamic characteristics. The response surface method based on the dynamic characteristics identification was adopted to update the FEM. And the influences of the paving,equivalent masses of adjacent bridges on the bridge ＇s natural frequencies were discussed. The results show that the FEM established is quite accurate,the paving will lead to the huge decrease of natural frequency,and equivalent masses of adjacent bridges have significant effect on the lateral and torsional frequencies.