考虑桥梁约束的桥墩复合基频近似算法

针对实际工程中桥梁上部结构对桥墩顺桥方向振动具有不可忽略的约束作用,在能量法的基础上推导出了顶端受桥梁约束的桥墩复合振动基频计算公式.将基频表示成各惯性元和复原元所组成子系统的频率合成,其中惯性元为桥墩自身分布质量和顶端附加质量,复原元为约束的变形、桥墩的弯曲变形和剪切变形.然后用有限元建模来验证该方法,并分析了顺桥方向约束刚度和墩顶附加质量对桥墩基频的影响.计算结果表明,导出的公式具有足够的精度,可以满足一般工程的要求.

Approximate algorithm of fundamental frequency of pier constrained by bridge beam

Because effect of upper bridge to longitudinal vibration of pier could not be neglected,fundamental frequency calculation formulas of pier restrained on its top by bridge beam were derived based on energy method.Fundamental frequency was presented as a composition of frequencies of several subsystem,which consisted of a deformation component and an inertia component.Inertia components include distributed mass of pier and attachment mass of upper structure while deformation components include constraint deformation,flexural deformation and shear deformation.Then FEM was used to verify the proposed method,and influence of factors on fundamental frequency such as upper structure longitudinal constraint and counterweight on top of pier were discussed.It is demonstrated that the algorithm is accuracy enough to meet the needs of practice.