Stress Concentration And Plastic Damage Of Concrete Surrounding Biased Dowel Bar In Rigid Pavement

Joint is an important but a weak part of rigid pavement.It can improve the Joint LoadTransfer Capacity by setting dowel bar at the joint.Due to the influence of constructin technology,construction quality and environmental factors,the dowel bar will deviate from its ideal position,which will limit its horizontal movement.The plastic deformation and damage of concrete around the biased dowel bar will occur in advance due to stress concentration.The concrete damaged plasticity(CDP)model was applied to study concrete damage at the concrete-dowel interface in rigid pavement,which was easily caused by stress concentration.The numerical simulation method was used to analyze the mechanical behavior of concrete around the unbiased dowel bar subjected to different axle loadings and temperature loading,and the mechanical behavior of concrete around the biased dowel bar subjected to standard axle loadings.The research contents of this paper are as follows:1.This paper introduced the theoretical basis of CDP model,which was based on the theory of plastic mechanics and damage mechanics,reflecting the decreasing of concrete stiffness with the development of plastic deformation by damage factor.According to the stress-strain full curve of concrete,the corresponding damage factor was calculated by the energy loss principle based on Gauss integral,and then the parameters of CDP model were derived.By comparing with the model testing stress-deformation results,the accuracy of CDP model parameters was verified.2.A three-dimensional solid finite element model of the rigid pavement with dowel bar in ideal place was established,which was used to analyze the distribution and involution of plastic strain,damage factor and equivalent stress around dowel bar at joint subjected to different axle loadings.The results indicate that when the load applys at the edge of the slab with the bonded end of the dowel,the stress status of the concrete around the bonded end of the dowel is most unfavorable.As the axle loading increases,the equivalent stress of concrete begins to decrease,and the plastic zone extends from 125°～235° to 30°～330° around the dowel.As a result,the concrete in the range of 145°～215° of the dowel involves to failure due to complete plastic damage,and the equivalent stress of concrete tends to zero,which leads to stress redistribution.Consequently,more loadings are contributed to the concrete at the both sides and at the top of the dowel.3.In order to discuss the influence of temperature on rigid pavement,the temperature gradient field was generated by using ABAQUS finite element software,which was linearly distributed along the thickness of concrete slab.The results indicate that the concrete slab may arch in the middle subjected to the positive temperature gradient,and the concrete near the smooth end of the dowel in the middle of the concrete slab will crack upward and downward through the plastic zone,resulting in the slab rupture.The corners of the concrete slab may arch subjected to the negative temperature gradient,and the concrete at the boths sides of the dowel at the boths ends of the concrete slab may be complete tensile damaged.4.Based on the three-dimensional solid finite element model of the rigid pavement,this paper studied the effects of horizontal and vertical tilts of dowel bar on concrete around dowel bar.The reults indicate that the plastic damage factor of the concrete around the dowel bar decreases first and then increases with the increase of the horizontal tilt angle of the dowel bar.When the horizontal tilt of the dowel bar is less than 6°,the plastic damage factor of the concrete will decrease compared with 0°,and the maximum reduction can reach-11.23%.But when the horizontal tilt of the dowel bar is greater than 9°,the plastic damage factor of the concrete will increase rapidly,and when the horizontal tilt reachs 12°,the growth of the damage is 51.44%.It is more disadvantageous for the dowle bar to tilt vertically clockwise than to tilt vertically anticlockwise.The plastic damage factor of the concrete around the dowel bar increases linearly wih with the increase of the clockwise vertical tilt angle of the dowel bar.When the clockwise vertical tilt reachs 12°,the growth of the damage is 90.28%.The equivalent stress of the concrete changes synchronously with the damage factor of the concrete.The larger the concrete’s damage factor is,the smaller the concrete’s equivalent stress is.