Concrete Pavement For Smart Truck Platooning:Topology Optimization And The Performance Investigation

Platooning is the trend of the smart trucks in the future.The smart truck platooning brings shorter headway time distance and smaller lateral offset,which makes the wheel track belt of pavement narrower,more concentrated force and significantly increase the frequency of load action Although the traditional dense and uniform pavement structure can meet the maximum load demand of the formation,it is not suitable with the differentiated load action and will significantly increase the construction cost,so it is necessary to explore the non-uniform refinement design method of the pavement structure.Therefore,based on the structural topology optimization theory,considering characteristics of the road engineering and cement pavement structure,this paper proposed a topology optimization method of cement pavement structure under smart truck platooning load,including topology optimization algorithm,and numerical method for solving the algorithm.Several prototypes of cement pavement structure have been designed and the basic mechanical performance of the prototypes has been verified.The main works and conclusions of this paper are as follows:(1)Based on literature research and data analysis,this thesis investigates loads of smart truck platooning.It shows that the shortest time distance of a stably running smart truck platooning is 0.3s,the offset of its wheel track is 15 cm,and the wheel track distribution standard deviation is 7.14 cm,merely 1/6 of the traditional traffic load.The number of load repetitions on wheel tracks can be 5～8 times higher than that of traditional traffic.Based on this,the scenarios of smart truck platooning are summarized and the load condition of cement pavement structure topology optimization design in each scenario has been proposed.(2)The requirements of the topology optimization algorithm are proposed from the demand for cement pavement in terms of service performance,service life,construction convenience and economy.The level-set method and the reactiondiffusion equation has been applied as the core of the algorithm according to the algorithm requirements,and the main optimization objective is set as to control the maximum fatigue stress of the pavement structure,which is subject to the structure weight constraint.The basic problem statement has been established,the sensitivity of the problem and the update method of the design variables using sensitivity are derived,and the general formula has been given,which compose the topology optimization algorithm of cement pavement structure for smart truck platooning.(3)Aiming at solving the topology optimization algorithm mentioned before,the numerical method for topology optimization method of cement pavement structure under smart truck platooning is proposed.The initial models according to scenarios of smart truck platooning has been established,the discrete method for the initial models has been clarified,and the range of parameter values for the numerical design has been suggested.Based on the numerical design method,several prototypes in different scenarios have been designed in two-dimensional and three-dimensional space.The maximum fatigue stress of the prototypes is reduced by 10% compared with the conventional cement pavement structure,and the weight of the structure is reduced by more than 50%.(4)To solve the chessboard pattern and gray material phenomenon of the prototype directly designed by the numerical design method,a post-processing method for the boundary of prototype based on the B-spline theory has been proposed.A finite element model of the cement pavement structure topology optimization prototype for smart truck platooning is established,and the mechanical performance of the prototype in each scenario is verified using static and dynamic load.The results show that the maximum fatigue stress of the prototype under each scenario are less than 75% of that in traditional cement pavement structure,and 14% lower than the calculation values in topology numerical design,also lower than the tensile strength of the material.A scaleddown model of the prototype structure was fabricated using polymer 3D printing technology,and the mechanical properties of the prototype structure were analyzed by single-point loading experiments.The results also showed that the mechanical properties of the prototype structure are less than 88% of those of the traditional cement pavement structure under the same loading conditions,and the difference with the theoretical value is 13%,proving the effectiveness of the topology-optimized design method.