基于行驶舒适性的路桥过渡段差异沉降控制阈值

Differential settlement control threshold at road-bridge transition section based on ride comfort

为解决传统路面结构路桥过渡段差异沉降过大和二次跳车问题,结合路桥工程实践,通过将桥头搭板放置一定深度和设置两级枕梁,并将桥头搭板与枕梁现浇在一起的方式,提出一种刚柔连续过渡的桥头搭板结构,用以改善桥头路基的应力分布及变形;同时为研究不同等级公路的路桥过渡段差异沉降控制阈值,给出量化指标,通过分析桥头跳车作用机理,根据车辆振动系统输入激励与输出响应的关系,建立二维五自由度车辆振动模型,并根据不同等级公路的路桥过渡段处治情况,建立相应的计算模型,编写程序求解人体加权加速度均方根值,根据人体舒适程度分级情况确定不同等级公路的路桥过渡段差异沉降控制阈值。结果表明:高速公路一级公路、二级公路和三级公路的路桥过渡段差异沉降控制阈值为将容许搭板纵坡变化值控制在0.30%~0.40%、0.40%~0.55%、0.50%~0.75%和0.95%~1.35%,四级公路的路桥过渡段差异沉降控制阈值为台阶高度控制在0.05m以内。

To address the issues of excessive differential settlement and secondary derailment in traditional road and bridge transition section,a approach slab structure with a rigid-flexible continuous transition is proposed.This design combines the practices of road and bridge engineering by placing the approach slab at a certain depth and incorporating secondary sleeper beams,which are cast-in-place together with the approach slab.The aim of this design is to improve the stress distribution and deformation of the bridge head subgrade.Quantitative indices were presented in order to study the differential settlement control threshold at road-bridge transition section of highways at different levels.Then,a two-dimensional five-degree-of-freedom vehicle vibration system analysis model was established in accordance with the relationship between input excitation and output response of vehicle vibration systems based on analyzing the action mechanism of bridge-head bumps.After that,calculation models were constructed in accordance with the treatments at the road-bridge transition section of highways of various levels.Differential settlement control threshold at road-bridge transition section of highways of various levels based on ride comfort was determined with the root-mean-square value of human comfort weighted acceleration solved by a written program.The results indicate that the control threshold at the road-bridge transition section of the highway is a longitudinal slope variation value controlled from 0.30%to 0.40%.Specifically,first-grade,second-grade,and third-grade highways are ranged from 0.40%to 0.55%,from 0.50%to 0.75%,and from 0.95%to 1.35%,respectively.Besides,the control threshold at the road-bridge transition section of the fourth-grade highway is the step height that should be controlled within 0.05 m.