高速铁路路桥过渡段动力特性受其刚度变异性影响的随机性分析

Stochastic analysis on influence of the parameter variability of subgrade stiffness on dynamic response of high speed railway subgrade-bridge transition zone

摘要:

路桥过渡段由于施工控制及填料的不均匀性而使其力学参数具有较大变异性,针对过渡段关键不确定性因素对其动力特性的影响以及过渡段动力设计的安全评估,运用铁路大系统动力学理论,并通过修正扣件弹簧的刚度矩阵实现钢轨梁与轨下基础平面模型的垂向传力耦合,同时引入无限单元法消除边界效应,建立高速铁路路桥过渡段车辆-轨道-线下基础系统垂向耦合振动模型；利用该模型,应用基于拉丁超立方抽样的随机有限元法,分析了过渡段路基刚度参数变异性对过渡段车-路系统动力响应的影响,结果表明：刚度参数的变异性对钢轨垂向动位移的影响大于对轮轨力及车体加速度的影响,且各动力响应主要对倒梯形部分填料的参数变化较为敏感；动力响应数据偏离正态性,在95%的置信水平下,过渡段轮轨力、车体加速度的最大值近似服从韦伯分布,钢轨垂向动位移最大值的数据分布则呈现明显的“高峰厚尾”,易出现异常大值,为减小钢轨垂向动位移以及便于施工质量管控,应适当提高过渡段路基刚度；选用钢轨垂向动位移最大值作为过渡段动力设计的安全评价指标,计算显示现行设计模糊失效概率为0.00045,失效概率较小,动力设计较为可靠。

Abstract:

Subgrade fillers in the vicinity of bridge abutments are very difficult to be well compact. And the material of subgrade fillers is inhomogeneous. As a result the variability of subgrade stiffness is observed. Focusing on the effect of the key uncertainties on the dynamic properties and the safety evaluation of the dynamic design of the transition zone, and based on the theory of the railway system dynamics, a plane strain finite-infinite element model is employed to investigate the system dynamics of a subgrade-bridge transition zone. In this model, the vertical force coupling for the rail and the substructure is achieved by modifying the fastening spring stiffness matrix and the infinite element method is employed to prevent the wave reflection on boundaries. With this model and the stochastic finite element method based on the Latin hypercube sampling method, The influence of the parameter variability of subgrade stiffness on dynamic response of vehicle-track coupling system in the transition zone is investigated. The results indicate that the influence of the variability of subgrade stiffness on the rail vertical dynamic displacement is greater than that of the wheel-rail contact force and the acceleration of the vehicle body. The dynamic response of transition zone is more sensitive to the parameter variability of the filler in the transition zone than that of the subgrade surface layer. Dynamic response data deviate from normality, and at the 95% confidence level, the maximum value of the acceleration of the vehicle body and the wheel-rail force approximately obey the Weibull distribution. While the data distribution of the maximum value of the rail vertical dynamic displacement presents obvious “high peak and thick tail”, and it is easy to appear the abnormal large value. In order to reduce the vertical dynamic displacement of the rail and facilitate the construction quality control, the subgrade stiffness of the transition section should be improved. The maximum value of the rail vertical dynamic displacement is selected as the safety evaluation index of the dynamic design of the transition zone and the result reveals that the fuzzy failure probability of the current design is 0.00045 and the design is safe.