Mechanics Properties Of Continuously Reinforced Concrete Pavement Under Temperature Load

The transverse cracks of CRCP is mainly caused by temperature shrinkage and concrete shrinkage.The slab of concrete pavement which is constrained by the foundation,lug and continuous longitudinal steel bars in the board can't deform freely. In order to accurately calculate the distribution and law of development of the CRCP's transverse cracks , based on the elementary theory of force method,on the foundation of existing research, considering the impact of foundation frictional resistance and the bond-slip effect between reinforced steel bar and concrete, and also considering the combined effect of every cracks and lug, the analytical solution of stress and displacement at any part of the CRCP is obtained.Compare to the existing compute theroy,it is more reasonable and reliable using the joint action of the entire road section for temperature effect compution. Make use of the analytical solution,the mechanical property of CRCP which is under the temperature shrinkage and concrete shrinkage have been studied and obtained the following conclusions:the larger the steel bar diameter is and the smaller the ratio of reinforcement is, the poorer integrity of CRCP is.Using"small dimeter and more numbers of steel bars", contact area between concrete and steel bars is increased, in the same time,the deforming ability of concrete which is constrained by the steel bars is improved.And then the slip between concrete and steel bars is decreased, the load transmission ablity of steel bars between every cracks have also been increased,therefore the resistance of deformation is improved and strengthen the integral performance of the road pavement.According to the increasing of restraining action of the lug,the foundation frictional resistance and the stress of lug is also increasing,leading to the width of cracks is reduced;With the increasing of slab thickness,the maximum stress of concrete and steel bars gradually reduced,and width of cracks is increasing.With the development of slab thickness,the internal forces of the foundation frictional resistance and lug is increasing,so it shows that the thicker the slab is,the more require of lug system is.According to the increasing of foundation frictional resistance coefficient,the stress of concrete and steel bars is also increasing.It means that with the increase of foundation frictional resistance,the deform ablity of CRCP which is constrained by the foundation and under temperature shrinkage is developed,and the width of cracks is also increased,so the load of the lug is relieved apprently and the maximum internal force of lug is reduced greatly.The stress of concrete and steel bars which is closing to the end of the lug is sensitive to the scale factors of foundation soil surrounded lug,but the scale factors of foundation soil has little effect to the stress of concrete and steel bars which is at the middle of the road section,and have finite effect to the numbers and width of cracks which is appeared in the middle of the road section, the scale factors of foundation soil also have large effect to the mechanical property of lug system.With the increase of scale factors,the anchorage ability of lug is strengtened,the internal force of lug which is under temperature shrinkage is increased,therefore the lug must have sufficient bending stiffness and bearing capacity at the design phase.The anchorage ability of pavement lug system can be increased effectively by augmented the size of lug which is closing to the end of the road section,and the foundation frictional resistance is also reduced,but in this case,the load of lug itself has been increased.When the thickness of lug is over 70 cm,it has little effect to anchorage ability.Compare to increasing the thickness of lug,increasing the deepth of lug is more efficent to improve the anchorage ability.However,increasing the deepth of lug,the thickness of lug must be increased properly as well,so the lug have the sufficient stiffness to resistent the bending moment .Basing on Displacement method, the warpage analytical solution of the CRCP derived by temperature is given,then analyze stress state of the CRCP with the the expansion joints in the case of seasons and sunshine temperature difference.In addition, the temperature stress and displacement of the CRCP with expansion joints about an actual projects is computed.And concluded that: The temperature displacement in CRCP tip with expansion joints increases due to the lack of lug restraints;the temperature gradient significant affect the stress on the concrete cross-section, especially the temperature warpage phenomenon can not be ignored in the end within the anchorage zone; the increasing of reinforcement rate and pavement thickness will result in a larger displacement and a longer anchorage zone in the end; we can through increasing the bar diameter and ground friction coefficient to reduce the displacement and the anchorage length in the end. The results provides more reliable theoretical basis for the future design.In order to analyze material nonlinearity of the impact of temperature shrinkage and shrinkage cracks, a new type of unit and its stiffness equations based on contact theory is established.It was established in accordance the actual work state of CRCP structure.it can deal with the presence of cracks, indicated foundation friction resistance at the bottom of concrete slab actually, indicated the actual arranged location of steel bars(not necessarily arranged in neutral layer).Considering bar&concrete adhesive stress and foundation friction resistance nonlinear constitutive relation and linear constitutive relation ,the author separately use finite element method to calculate. Results show that the difference between the two situation was large, CRCP design should take into account non-linear effects. Then the author used finite element method to analyze transverse cracks development, the calculation results were compared with available observational data.The Comparing results show that the finite element solution can be a very good prediction of the distribution and development of cracks in CRCP. It is a reliable and practical method.The author investigated the impact on the CRCP top surface stress affected by vertical location of the reinforcement.The calculation results showed that the continuous axial reinforcement should be arranged at a distance to the top of 1/2~1/3 thickness,when the stress minimum, verified the principles in standard. The author also analyzed development of CRCP cracks in the Changchun area which constructed in the different month.The average crack spacing decreased increases with time gradually increases;the number of cracks were gradually increased; crack spacing reduced rate changes over time more and more slowly, new cracks add fewer and fewer.Under normal circumstances, the development of cracks after a year of an overall cooling process, gradually stabilized.