中文摘要：

分别讨论并比较在不同跨径比下的连续梁的固有频率及振型的变化规律和异同点。试验梁采用槽型梁,除了对模型进行固有振动分析和理论计算外,还采用有限元软件分别对各个跨径比下的试验模型进行有限元计算分析和计算。以有限元的计算结果作为参考,同传统检测试验得到的结果进行对比分析,论证振型变化规律的真实性。结果表明：对于不同跨径的对称四跨连续梁,支座对称移动时,前3阶振型始终对于中支座是对称或者反对称的,并且中支座在2阶振型中首先出现反弯点。当计算跨中正弯矩效应时,冲击系数按照《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2阶频率进行计算。

英文摘要：

The natural frequency of the four-unequal-span continuous beam is analyzed and the changes of natural frequencies and vibration modes of the continuous beam are discussed with different span ratios. In test U-shaped beam is chosen. In addition to the natural vibration analysis and theoretical calculation of the model,finite element software is used to analyze and calculate the model with each span ratio. The results of finite element method are taken as references,and are compared with those obtained by traditional test,it proves the authenticity of the change law of mode. The results show that for the symmetric and four-unequal-span continuous beam, when the bearings are symmetrically moved,the first three modes of vibration are always symmetric or antisymmetric for the middle bearing,and the first bending point appears in the second vibration mode. For the mid span positive moment effect,the impact is calculated according to ＂ bridge gauge ＂; for the negative moment effect of bearing,the impact factor should be calculated with second order frequency.