西宁北川河钢管混凝土拱桥的理论和实验模态分析

Experimental and analytical modal analysis of a CFT arch bridge over Xining Beichuan River

对西宁北川河钢管混凝土拱桥进行了理论与实验模态分析,该桥为中承式钢管混凝土系杆拱桥,净跨90m,桥面净宽21.6m。本文首先介绍了现场环境脉动实验概况,利用频域中的单模态识别法(SDOFI)、峰值法(PP)和时域中的随机子空间识别法(SSI)分别进行桥梁动力参数识别;利用ANSYS建立了全桥三维有限元模型,并进行了参数修正,理论和实验模态分析结果具有相当好的吻合程度。参数分析表明:不同规范的动力特性计算结果是有一定差别的。此类测试和分析可以提供结构健康监测的基准模型,服务于结构状态评估和修复。

The paper presents the experimental and analytical modal analysis on a concretefilled steel tubular(CFT) arch bridge over the Beichuan River in Xining, Qinghai Province, China. The arch bridge is a halfthrough CFT bridge, with the span of 90 m and the width of 21.6 m. The field test is carried out conducting ambient vibration testing under trafficinduced excitation. The SingularDegreeofFreedom identification (SDOFI) method and the peak picking (PP) method in frequency domain and the stochastic subspace identification (SSI) method in time domain are used for the outputonly modal identification. A good agreement in identified frequencies has been found among these methods. The 3D finite element models (FEM) are constructed and an analytical modal analysis is then performed to generate natural frequencies and mode shapes in the 3orthogonal directions. The finite element model is validated to match the field natural frequencies and mode shapes of the bridge. The parameter analysis indicates that the dynamic calculations from different design codes are different. It is further demonstrated that the results from the FEM agrees well with the field tests and can serve as a baseline model in the seismic evaluation/retrofitting of the bridge.