温度对桥梁模态参数的影响

Influence of Temperature on Modal Parameters of Bridge

从理论上推导了温度对简支梁频率的影响公式,并对一个独塔组合梁弯斜拉桥进行了温度效应和频率影响分析,提出了利用有限元计算来量化温度对复杂结构频率影响的方法.结果表明:环境温度主要通过使结构尺寸变化、使超静定结构产生内力以及使结构材料的力学性能发生改变这3种方式影响结构模态频率,其中结构尺寸变化的影响可以忽略不计;环境温度对结构模态频率的影响程度主要取决于结构形式、材料、截面大小以及结构内力状态.实例分析显示:不同温度模式对结构变形和内力的影响差别很大;体系温差对斜拉桥频率的影响主要是由弹性模量随温度的变化而引起的;主梁温度梯度对频率的影响体现在温度内力的改变上,而索梁温差和索塔温度梯度对频率基本无影响.

In this paper, a theoretical formula describing the temperature effect on the frequency of simply-suppor- ted beam is deduced. Then, by taking a single-pylon cable-stayed bridge with curved composite beam as the ob- ject, the temperature response and the effect on the frequency are analyzed, and a finite element method is pro- posed to quantify the effect of ambient temperature on the frequency of complex structures. The results show that （1） ambient temperature influences the modal frequency of the bridge structure mainly in three ways, namely, changing the structural size, producing internal force in the statically indeterminate structure and changing the me- chanical properties of the structural material ; （2） the influence of structure size change on the modal frequency can be neglected ; and （3） the influence degree of ambient temperature on the modal frequency mainly depends on the structure form, the material, the section size and the internal force state. Moreover, case study results indicate that （ 1 ） different temperature modes have different influences on the deformation and the internal force of the structure ; （2） the influence of uniform temperature on the modal frequency of cable-stayed bridge is mainly due to the change of elastic modulus, while the influence of girder temperature gradient is mainly due to the change of internal force ; and （3） neither the cable temperature difference nor the pylon temperature gradient has any significant influence on the modal frequency.