矮塔斜拉桥竖弯频率的能量法估算实用公式

为方便计算矮塔斜拉桥的竖向自振频率,基于双塔塔梁固结、墩支承的矮塔斜拉桥,应用Rayleigh法,推导了一阶对称和反对称竖弯振动频率公式,提出了名义单位质量的抗弯刚度的概念,对此公式的可行性进行了算例验证,并讨论了该公式的应用对象.研究结果表明:支承条件对该体系的竖弯频率影响较大,进行频率计算时应准确考虑支承条件;给出的能量法得到的竖弯基频计算值与有限元值误差能满足概念设计阶段的要求;该公式适用于双塔塔梁固结、墩支承的矮塔斜拉桥,抗风设计规范中的竖弯基频公式不适用于此类桥梁.

Estimation Practical Frequency Formulas for Vertical Vibration of Extradosed Cable-stayed Bridge Based on Energy Method

To calculate vertical frequency of extradosed cable-stayed bridge conveniently, a extradosed cable-stayed bridge with double-towers was taken as a research object, while the tower was rigidly connected with the girder and supported by the pier. Frequency formulas for the first symmetric and asymmetric vertical vibration modes were induced by the Rayleigh method and the nominal unity mass anti-bending rigidity concept was proposed. Finally, the presented theoretical formulas were validated by the engineering project, and the application condition was discussed. The results indicate that constraint condition has a great influence on vertical frequency, which should be correctly considered in frequency calculation. The error between values calculated by the proposed formulas and the finite element method ( FEM) meets with the requirement of conceptive design. The proposed formulas can be applied to extradosed cable-stayed bridge, but the vertical frequency formulas in the wind-resistant design specification cannot be applied to the such bridge.