五等跨连续梁模态分析试验及冲击系数

Modal Analysis Test to a Five Equal Spans Continuous Beam and Study of Impact Factor

分析计算五等跨连续梁的固有频率和振型,探讨连续梁桥冲击系数与其固有频率和振型的关系,并进行了连续梁振动试验,试验模型采用槽型梁,支撑方式采用钢锟轴支撑,试验结果运用DASP模态分析软件进行处理,得到五等跨连续梁的前5阶振型及频率。利用Midas有限元分析软件对连续梁进行有限元分析,将其计算结果与试验结果进行对比,证实振型变化的真实性。经过试验分析,连续梁的前5阶振型最大曲率位置被确定,结合规范讨论计算冲击系数时结构固有频率的选取。结果表明:当计算跨中正弯矩效应时,冲击系数宜按照《桥规》采用基频计算;当计算中支座负弯矩效应时,冲击系数应采用第3阶频率。

The natural frequency and vibration mode of 5 equal spans continuous beam was analyzed,the relation between the impact factor of continuous beam and the natural frequencies and vibration mode was discussed,and these dynamic parameters of continuous beam modal were measured. Test model used groove type beam,supporting way was with steel shaft support,the DASP equipment was used for modal analysis to obtain the first five vibration modes and frequencies of 5 equal spans continuous beam. The finite element analysis software Midas was used for continuous beam.The simulation results were compared the measured data,the authenticity of the vibration mode change was verified.From the test analysis,the locations of the maximum curvatures of the mode shapes were determined,the selection of the natural frequency of the beam was discussed with the design code. It is shown that,when calculating the effect of positive bending moment at steady,the fundamental frequency should be used as shown in the general code to calculate the impact factor; when calculating the effect of negative bending moment at middle fulcrum,the 3rd frequency should be used.