体外预应力混凝土简支梁固有频率研究

为研究预应力与固有频率间的关系和影响固有频率变化的因素,对3根体外预应力混凝土简支梁分级施加预应力并进行动力测试,然后使用MATLAB软件根据试验数据拟合刚度公式,并将计算结果与试验值进行对比分析,结果表明:预应力梁的自振频率受支座约束形式和体外预应力筋偏心距与布置形式的影响大于预应力自身对频率的影响,预应力效应是多种因素共同作用的结果,固有频率总体上随预应力的增加而增大;经过刚度修正后的公式能较好的反映自振频率随预应力的变化趋势,一阶频率的计算值与试验值符合得很好;二阶频率的计算值和试验值误差较大,有待进一步研究;三阶频率易受其他因素影响而失真,缺乏研究的价值。

A study on natural frequency of simply supported externally prestressed concrete beams

In order to study the relationship between prestress and natural frequencies and the factors which influence natural frequencies,a dynamic test on three simply supported externally prestressed concrete beams of different prestressed level was carried out.Then a stiffness formula is derived by fitting the test results with the software MATLAB and comparing the calculated results with the test ones.The results indicate that the eccentricity and arrangement of externally prestressed tendons and the constraints have more influence on the natural frequencies than the prestress itself;that the prestressed effect comes from the combined action of the several factors;and that the natural frequcencies of beams grow with the prestress.It also indicates that the modified stiffness formula can well reflect the variation of the natural frequencies with the prestress.The calculated results of the fundamental frequency are in good accordance with the test results,but the error of the second-order frequency is bigger,which needs further studies.The third-order frequency is lack of research value because of the serious distortion due to other influences.