Reserch On Mechanical Behavior And Optimization Of Prestressed Concrete Pavement In Horizontal And Vertical Curve Road Section

Prestressed concrete pavement(PCP)can effectively improve mechanical performance and extend service life of road by applying longitudinal and lateral prestress in concrete slab.Meanwhile,PCP can reduce the number of expansion joints and improve ride comfort.However,researches on PCP confine chiefly to straight road section and are lack of studies on PCP in horizontal and vertical curve road section currently.Therefore,in this paper,the effects of horizontal and vertical curve factor on layout of prestressed tendons and mechanical behavior of PCP are analyzed,and feasible prestressing schemes of PCP are proposed based on current researches on PCP.According to designed pavement structure,the finite element analytical model is established to analyze the mechanical behavior of PCP in horizontal and vertical curve road section during construction and service stage.Based on mechanical characteristics of the pavement,optimization measures are proposed,and an evaluation indicator is established to evaluate the mechanical property of PCP in horizontal and vertical curve road section.In horizontal curve road section,there exists difficulty in arranging longitudinal prestressed tendons into circular curve and the angle between diagonal prestressing tendons and road slab is not a uniform value,while there are generally few effects for the factor of vertical curve due to large curve radius.Therefore,in horizontal curve road section,longitudinal prestressed tendons can be arranged by fitting the curve prestressed tendons with segments of straight line,and diagonal prestressed tendons can be arranged by controlling the angle with road center line.In vertical curve road section,prestressed tendons can adopt the arrangement way same as that in straight road section.In construction stage,the prestress distributed in the middle of PCP slab is relatively evenly,and there is stress concentration at the anchoring end of prestressed tendons.Due to the influence of friction and other factors,the actual prestress level in the slab is slightly less than the design value.the prestress level in concrete slab applied by bonded prestress is slightly higher than that applied by unbonded prestress,and prestress distributes more uniformly.In horizontal curve road section,the uniformity of prestress distribution in concrete slab is worse than that in straight road section.In vertical road section,the prestress level of PCP is slightly larger than that in straight road section.In service stage,the stress caused by vehicle load is the largest in vertical road section,the second in straight road section,and the least in horizontal curve road section.However,the thermal stress is similar in the three kinds of road section.From vehicle approaching to leaving,the compressive stress at the bottom of concrete slab first rise slightly,then sharply decline,and finally return to initial level in the acting area,which is opposite to the stress variation trend at the top of concrete slab.The daily variation of temperature at different depth of concrete slab fluctuates as sine function,and with the increase of the slab depth,the phase of temperature variation curve lags.In general,thermal stress is larger in the middle of road slab than on the periphery.According to the stressing characteristics of PCP in horizontal and vertical curve road section,several optimization measures are put forward in this paper including central stressing of longitudinal and lateral prestressed tendons,the comprehensive diagonal prestressing scheme and anchoring concrete slab to base course in the middle of the slab in vertical curve road section.Extended finite element method and energy method are used to evaluate crack resistance and fatigue performance of PCP in horizontal and vertical curve road section from aspects of bearing capacity limit state and fatigue limit state.Researches show that the most unfavorable load will not cause crack or promote crack propagation in PCP with design flexural-tensile strength;the ability of PCP to resist crack initiation and expansion and fatigue damage is superior to that of plain cement concrete pavement;among the three types of PCP,the mechanical properties of longitudinal and lateral PCP are the best overall.