OPERATIONAL MODEL IDENTIFICATION AND CALIBRATION OF CFST ARCH BRIDGE BASED ON AMBIENT EXCITATION
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摘要: 为了对已经运营多年的钢管混凝土拱桥结构的抗震性能进行验算和评估，以一座钢管混凝土拱桥的实际工程为例，建立其用于抗震分析的初始有限元动力模型，利用设置在拱桥上的健康监测系统，在环境激励下，采用FDD法对实际结构的工作模态进行识别，依据识别结果采用零阶近似法对初始有限元模型进行了修正。通过模态识别到模型修正的途径，可以将健康监测系统与抗震分析联系起来，为抗震分析提供一个基于实际状态的更为准确的动力分析模型。结果表明：FDD法可以准确识别出钢管混凝土拱桥的前5阶模态，具有良好的识别效果；主拱肋、稳定拱、吊杆、横撑和主梁所对应的材料特征值在修正前后的变化量为8。77%~10。21%，对结构动力特性有显著的影响；采用零阶近似法对模型进行修正后可以得到满意的结果，计算频率与实测频率的误差可缩小至0。11%~3。76%，修正后的模型能更为准确的体现实际状况，从而可以对已运营多年的桥梁结构做进一步抗震验算和评估。Abstract: To conduct the aseismic analysis of concrete-filled steel tube (CFST) arch bridges,the initial finite element model of a practical and operational CFST arch bridge is derived. Meanwhile,a more accurate and up-to-state dynamic analysis model for aseismic analysis can be derived through the modal identification and calibration techniques. Thus,this paper is to bridge the gap between the health monitoring techniques and aseismic analysis for large-span bridge structures. With the employment of the ambient response histories from a health monitoring system of this bridge,the operational modal parameters are identified by the FDD method,the FE model has been calibrated using a zero-order approximation method then. Results show that the FDD method can well identify the modal parameters and satisfactory results are observed in using the zero-order approximation method for the model calibration. The error between calculated and measured frequencies can be reduced to 0.11%~3.76%,and the variations of material properties (8.77%~10.21%) have significant effects on the structural dynamic behavior. The calibrated model,reflecting the practical state of a structure,can be used to assess the aseismic behaviors of operational bridge structures in the further.
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