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Fatigue reliability assessment of simply supported bridges subject to impact of stochastic vehicle loads[J].计算力学学报,2018,35(4):417~423

Fatigue reliability assessment of simply supported bridges subject to impact of stochastic vehicle loads
Fatigue reliability assessment of simply supported bridges subject to impact of stochastic vehicle loads

DOI：10.7511/jslx20170422001

 作者 单位 E-mail 罗媛 长沙理工大学 土木工程学院, 长沙 410114南方地区桥梁长期性能提升技术国家地方联合工程实验室, 长沙 410114 颜东煌 长沙理工大学 土木工程学院, 长沙 410114 袁明 长沙理工大学 土木工程学院, 长沙 410114 luoyuanbridge@163.com

为了研究考虑随机车辆冲击效应的简支梁桥疲劳安全水平，提出了基于车-桥耦合振动与随机车流的桥梁疲劳应力谱模拟方法，并应用于疲劳可靠度评估。基于某高速公路桥梁动态称重数据建立随机车流模型，采用小样本车辆数据拟合桥梁等效疲劳应力范围的插值响应函数，最后由高斯混合模型拟合大样本随机车流作用于桥梁构件的疲劳应力谱。分析了25 m标准跨径简支T梁桥底部普通钢筋的疲劳应力谱，评估了考虑路面劣化与交通量增长的桥梁疲劳可靠度。数值分析结果表明，基于随机车流模拟的疲劳应力谱具有典型的多峰分布特征，包含了超载车辆产生的疲劳应力；车辆对桥梁的冲击效应致使等效疲劳应力放大系数略大于冲击系数，当路面等级为一般时，采用规范冲击系数将低估车辆冲击效应的疲劳损伤；路面劣化与交通量增长均会导致桥梁运营期内的疲劳可靠指标显著降低，由路面劣化导致车辆对简支梁桥的冲击效应不可忽略。

In order to investigate the fatigue safety of simply supported bridges subject to dynamic impact of stochastic vehicles,a new approach was presented for fatigue stress spectrum simulation of bridges based on vehicle-bridge coupled vibration and stochastic traffic flow.The approach was subsequently applied to fatigue reliability assessment.Stochastic traffic flows were simulated based on highway bridge weigh-in-motion measurements.An interpolation response surface function of the equivalent fatigue stress range was approximated by a small size vehicle sample.Probabilistic model of the fatigue stress was built by the Gaussian mixture functions.The fatigue stress spectrum of a typical simply supported T-girder bridge with a span length of 25 m was simulated.The fatigue reliability of the bridge was estimated accounting for road surface degradation and traffic growth.Numerical results indicate that:the stress spectrum simulated by the stochastic traffic load model has the characteristic of a multi-peak distribution,and the fatigue stresses due to overloaded vehicles were included in the spectrum model.The amplification factor of the fatigue stresses is larger than the impact factor resulting from the impact effects of vehicles.As a result,for an average road surface case,the fatigue damage due to the vehicle impact will be underestimated by the impact factor evaluated according to the design specification.Road surface degradation and traffic growth significantly decrease the fatigue reliability of the bridge in service period.The impact effect of vehicle on the simply supported bridges due to road surface degradation cannot be neglected.