盐湖地区RC桥梁结构时变车桥耦合振动寿命预测研究

A study on the life prediction of time-varying vehicle-bridge coupling vibration of reinforced concrete (RC) bridge structures in Salt Lake Area

盐湖地区氯离子侵蚀环境下,RC桥梁结构时变车桥耦合振动是一个复杂的多因素、高度非线型过程,且随着列车运行速度的增加,这种特性逐渐增强,因此,对于使用寿命评估需要更高要求的预测模型。采用二系主动悬挂系统建立RC桥梁车桥垂向耦合振动模型,基于虚拟激励法,求解列车在不同运行速度时的垂向振动位移,并以该位移和能量守恒定律为条件,确定荷载影响因子f(δ)的取值。基于Fick第二扩散定律理论,充分考虑混凝土氯离子扩散系数的时间依赖性、轨道不平顺激励及高速列车运行速度对RC桥梁结构垂向振动影响等因素,得到一种既考虑荷载影响因子f(δ)又考虑氯离子结合能力的RC桥梁氯离子扩散修正模型。仿真实验结果表明,与传统的未考虑列车运行速度影响因素的氯离子扩散模型相比,所提出的RC桥梁氯离子扩散修正模型更加合理,对于盐湖地区既有RC桥梁结构使用寿命的预测将更有实际工程意义。

The time-dependent vehicle-bridge coupling vibration of reinforced concrete(RC)bridge structures corroded by chloride attack is a complex multi-factor and seriously non-linear process in Salt Lake regions.The characteristic is gradually enhanced with wind speed and train speed,which results in higher requirement prediction model for life prediction assessment of RC bridge structures.A vehicle-bridge vertical coupled vibration model of RC bridge was established based on the secondary active suspension system.Based on the pseudo-excitation method,the vertical vibration displacement of the train at different running speed was solved,and the influence factors of load f(δ)were determined by the displacement and the energy conservation law.Based on the theory of the Fick second diffusion law,the time dependence of chloride diffusivity of concrete,the influence of track irregularity excitation and the running speed of high-speed train on the vertical vibration of RC railway bridge members were fully considered.Therefore,a modified model for the chloride diffusion of RC bridge was established,which considers both the influence factor of load f(δ)and the chloride binding capacity.The simulation results show that compared with the traditional chloride diffusion model without considering the influence factors of train running speed,the modified chloride diffusion model of the RC railway bridge is more reasonable.It is more practical for predicting structural service life of existing RC bridges in the Saline Lake regions.