The Research In The Beam-on-foundation In The Anchored End Of Continuously Reinforced Concrete Pavement

This paper mainly studies the stress state of the beam-on-foundation in theanchored end of continuously reinforced concrete pavement (CRCP) and presentsdesign method. The paper consists of five chapters totally. The emphasis parts arechapter two and chapter three.Chapter one mainly talks about the study background, content and method. TheCRCP is a kind of high performance concrete pavement structure with enough steel inthe longitudinal direction. In addition, joints are excluded in the course of theconstruction. It has been widely used in many developed countries because of its goodperformance. This structure is used sequentially in the United States, Belgium, France,Britain and etc. The application and correlative study about CRCP is relatively late inour country. With the development of high-grade road and the improvement in therequirement of pavement performance, it is sure that CRCP will be widely applied inhigh-grade road in our country. CRCP will move periodically when the temperaturevaries seasonally as a result of no expansion joints and contraction joints. This resultwill cause danger to pavement, bridges, culverts and other structures that are directlyconnected to the CRCP. Therefore, measurements are must be taken to restrict thedisplacement in the end. The beam-on-foundation in the anchored end has been widelyapplied as one kind of simple and applicable form in the end disposal.Chapter two introduces the calculation of displacement and stress of thebeam-on-foundation in the anchored end using the matrix displacement. According tothe study result, the calculation result of the force in the anchored end is gained, takingthe nonlinear distribution to which the friction force between subgrade and concreteconforms as the hypothesis. The three indexes such as friction force between subgradeand concrete, maximum temperature drop and allowable displacement influence thecalculation result significantly. The basic size of the beam-on-foundation is determinedpreliminary according to the analysis that is made in the influence of the height, thespace and the width of the end walls on the displacement and design load ofbeam-on-foundation. In addition, the interaction between the end wall and subgrade isalso taken into consideration. Furthermore, in the hypothesis of simplifying the volumestructure of the end wall into the member structure, considering concrete and subgradeas linear elastic material, taking the action of subgrade on the end wall as spring supportand ignoring the friction force between the surface and subgrade, the displacement andstress of the beam-on-foundation is calculated by means of matrix displacement method.Also, the influence of design parameters on the calculation result is analyzed in thispaper. Finally displacement and design load of the beam-on-foundation in the anchoredend are brought forward. And this provides accordance for the reasonable design ofbeam-on-foundation in the anchored end.Chapter three refers to calculating the displacement and stress of thebeam-on-foundation in the anchored end using the finite element method. The finiteelement model is established with the hypothesis as follows: taking concrete andsubgrade as the linear elastic material, meanwhile, ignoring the friction force betweenthe end wall and subgrade. Larger contact stress and displacement will form on accountof the difference in the stiffness between the end wall and soil. However, the analysisfunction of rigid bodies-flexible bodies contact provided by finite element softwareANSYS can reflect this practical case better. This chapter calculates the displacement ofthe beam-on-foundation in the anchored end, maximum tensile stress of the end walland maximum tensile stress in the pavement and analyzes the influence regularity ofmain parameters. The comparison is made in aspects of influence regularity andexamples between matrix displacement and finite element method. And the comparisonresult proves that the influence of design parameters on calculation result is basicallythe same for the two methods. The displacement obtained from the comparison betweenthe practical examples is also approximate. Maximum error is 3%. However, the stressdiffers greatly, and the error is 16.3%. The matrix displacement method can substitutethe finite element method, since the most important design index is displacement, andthe stress error influences the steel ratio indistinctly.Chapter four introduces the design method of the beam-on-foundation in theanchored end. The design includes three procedures as follows: the determination of theanchor force in the end, the calculation of the displacement and stress of thebeam-on-foundation and the steel design. The design of beam-on-foundation in theanchored end not only requires calculating the resisting capacity but also checking thecompatibility of deformation condition. Considering that the displacement from thecalculation is equal to the allowable displacement, the calculation result is justcreditable. Meanwhile, the beam-on-foundation in the anchored end should be used inthe section with good soil. The compaction carried out in subgrade in the region ofCRCP end anchor should be sufficient. When construction is conducted in the end forCRCP, the beam-on-foundation in the anchored end should be constructed first. Thefoundation pit can be excavated according to the design size without using mould.Generally speaking, the beam-on-foundation in the anchored end cannot restrict thepavement deformation completely. Therefore, it is necessary to set up an expansion joint,which has the same structure with that of the Portland concrete pavement. The use ofexpansion joint together with it can be taken into account if bridge is the jointedstructure.Chapter five is the summary of the paper. This chapter not only summarizes theconclusion obtained from the paper but also puts forward to the content and direction tobe studied in future.