考虑非平稳因素的大件车与普通车流混行中小跨径桥梁安全评估

Safety Assessment of Short-and Medium-span Bridges with Mixed Traffic of Customized Transport Vehicles and Ordinary Vehicle Flow Considering Non-stationary Factors

为满足大件运输车辆与普通车流混合通行中小跨径桥梁安全评估的紧迫需求,提出了基于分项系数模式的混行车流通行桥梁可靠度评估方法。首先,输入考虑空间相关的路面不平整度,建立混行车流-桥梁耦合振动分析系统;其次,根据WIM系统实测车流数据,综合考虑分车道荷载差异与车辆特征参数相关性模拟普通车流荷载,在极值理论框架下将非平稳车载过程离散化建立混行车流极值模型;然后,基于可靠度理论开展对评估基准期、目标可靠指标及分项系数校准问题的研究,并确定了抗力非平稳退化模型;最后,采用构建的评估方法对工程实例开展应用分析。结果表明:混行车流相比大件车单车居中过桥的结构响应增幅可达到30%以上;普通车流模拟结果中重载货车的轴重、轴距分布均匀,与实际车流的分布特征基本相符;基于历史交通量确定的Logistic函数可较好地描述交通量非平稳增长规律;单次混行车流通行桥梁的目标可靠指标受混行车流年均通行次数的影响,呈现增长放缓的趋势;基于Gamma随机过程的抗力非平稳退化模型与连续不间断的退化进程相适应;通过对实例桥梁的安全评估,经校准后的分项系数对交通量增长不敏感,抗力退化相比交通量增长对混行车流通行安全的影响更为显著,综合考虑二者非平稳因素对结构安全评估尤为重要。所建立的评估方法可为大件运输车辆与普通车流混行中小跨径桥梁的安全评估提供参考。

To meet the urgent need for the safety assessment of short-and medium-span bridges with a mixed traffic of customized transport vehicles and ordinary vehicle flow,a reliability assessment method for mixed traffic bridges based on the partial coefficient mode is proposed.First,a mixed vehicle flow-bridge coupling vibration analysis system is established,considering the spatially related road roughness as the input.Second,according to the measured traffic flow data of the WIM system,the normal traffic flow load is simulated considering the correlation between the difference of the divided lane load and the vehicle characteristic parameters,and the non-stationary vehicle load process is discretized to establish the extreme value model of mixed traffic flow under the framework of the extreme value theory.Subsequently,the assessment base period,target reliability indicators,and calibration partial coefficients are investigated based on reliability theory,and a non-stationary resistance degradation model is established.Finally,the evaluation method is applied to an engineering case.The results show that the structural response of mixed traffic flow can increase by more than 30%compared to the traffic flow involving a customized transport vehicle crossing the bridge with a single vehicle in the middle.According to the simulation results of ordinary traffic flow,the axle load and wheelbase of heavy-duty trucks are evenly distributed,which is consistent with the distribution characteristics of an actual traffic flow.The logistic function description based on historical traffic volume can better reflect the non-stationary growth law of traffic volume.The target reliability indicator of a bridge passing through a single mixed traffic flow is influenced by the average annual number of mixed traffic flows,which shows a slowing growth trend.The non-stationary resistance degradation model based on gamma random processes is adapted for continuous and uninterrupted degradation processes.A safety evaluation of the bridge in the case study reveals that the calibrated partial coefficient is insensitive to traffic volume growth.The impact of resistance degradation on mixed traffic flow safety is more significant compared to the effects of traffic volume growth.Considering the non-stationary factors of both aspects is particularly crucial when assessing structural safety.The established evaluation method can provide a reference for the safety assessment of short-and medium-span bridges with a mixed traffic of customized transport vehicles and ordinary vehicle flow.