摘要
针对土木工程结构模态识别中环境温度变化对结构频率的影响,基于模态参数的损伤识别方法,对3根混凝土模型梁在环境温度变化、不同程度结构损伤状况变化下进行振动测试,对结果进行理论和实验模态分析,得到了温度、损伤对于混凝土梁自振频率的影响曲线,混凝土梁频率对于温度变化具有一定的敏感性,对一座钢筋混凝土人行天桥在不同温度下进行实际监测,监测数据理论分析得到频率和模型试验研究结果基本一致,说明温度对于混凝土桥梁的频率具有一定的影响,在目前混凝土桥梁结构检测中必须引起重视。
本文主要作了以下工作:
1)通过Midas/civil分析钢筋混凝土梁和一座人行天桥的模型,用有限元方法模拟分析出结构的模态参数固有频率和振型;
2)对于钢筋混凝土梁模型,采用DASP2006采集及分析系统对模型进行采样,利用锤击激励的方法进行强迫振动,并利用DASP2006中特征系统实现法和随机子空间法两种方法分析,分析结果与有限元计算结果比较。结果表明,在室温为摄氏10度时,有限元分析结果与特征系统实现法及随机子空间法的实测模态参数结果基本吻合。然后在不同温度条件下采集分析模型的模态参数,发现环境温度的变化对结构模态参数有明显的影响;
3)为验证试验分析结果,利用环境激励法对一座钢筋混凝土人行天桥在不同温度下进行实际监测,监测数据与理论分析得到频率和模型试验研究结果基本一致,说明温度对于混凝土桥梁的频率具有一定的影响。
Aimed at considering the influence of ambient temperature on the frequency of civil engineering during modal identification, based on the damage detection method of the modal parameters, 3 concrete model beams were tested considering the ambient temperature changing and different damage, the experimental modal were extracted and analysis, the curves of frequency of the beams changing with the ambient temperature and crack were obtained , it is shown that the frequency of concrete beam is sensitive to the environmental temperature, one concrete footbridge was monitored under ambient vibration at different temperatures, the modal frequencies extracted from the monitoring data basically correspond with the experimental results. The temperature has a certain impact on the frequency and should be taken into account during the dynamic test of the concrete bridge.
The mainly work in this paper as follows:
1) The modal parameter of the concrete model beams and the concrete footbridge were analyzed by the software of Midas/civil software to get its modal frequency and damping.
2) The DASP2006 acquisition and analysis system is used to sample and analyze modal parameter and hammering method is used. Eigen-system realization algorithms and stochastic subspace identification in DASP2006 are used to analysis, and result of it analysis compare with the Finite element analysis, it shows that the results of the measured and simulation of finite element are within acceptable agreement at 10℃.Then modal parameter of beam is sample and analyze under different ambient temperature, it found that the temperature has a certain impact on the modal parameter concrete beam.
3) In order to verify the result of the analytic, one concrete footbridge was monitored under ambient vibration at different temperature; the modal parameter extracted from the monitoring data basically correspond with the experimental results, it shows that the temperature has a certain impact on the modal parameter of concrete footbridge during the dynamic test.
引文
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