Experimental Study On Fatigue Performance Of Fiber Composite Reinforced UHPC Double-Block Ballastless Track Slab

Although CRTSI double-block ballastless track slab has been widely used in high-speed railway lines in China.However,the ballastless track slab is a reinforced concrete structure.The closed loop formed in its interior and the ordinary concrete poured on its track slab bed greatly reduce the signal transmission distance of track circuit and the durability of the structure,which will become the bottleneck of the development of ballastless track.Steel continuous fiber composite bar(SFCB)is a new type of composite material with fiber wrapped inside the steel bar.In addition to good insulation,high strength,and durability,SFCB also has advantages such as good ductility,and stable secondary stiffness.Ultra High Performance Concrete(UHPC)is a high-performance concrete made from cement,fine aggregate,various fibers,admixtures and water.It has high strength(up to four times the strength of ordinary concrete),high toughness,low porosity,good durability,and large deformation capacity(up to 3500 peak microstrain).Based on the excellent durability of UHPC in harsh environments and the excellent insulation and mechanical properties of fiber composite reinforcement.Replacing the steel bars and ordinary concrete in the traditional ballastless track slab with the two materials is expected to solve the problems of the closed circuit and insufficient durability of the traditional ballastless track slab.As the stress characteristic of ballastless track slab is fatigue load,the fatigue performance test of fiber composite reinforced UHPC double block ballastless track slab is carried out in this paper to understand its fatigue performance.The specific content is as follows:(1)Perform tensile tests on SFCB reinforcement and HRB400 to obtain material properties such as yield strength,tensile strength,and elastic modulus of the reinforcement material.(2)The design principle of equal rigidity of section is adopted for the design of components.The track slab bed is poured with UHPC,and the fiber composite reinforced UHPC double block ballastless track slab is obtained.(3)Completed the experimental study on the fatigue performance of four fiber composite reinforced UHPC double block ballastless track slabs,describing the failure process and failure pattern of the components under fatigue load,and the change rules of cracks,deflections,stress bar strains,and UHPC strains in the compression zone of the ballastless track slab with the number of fatigue cycles under corresponding fatigue load cycles.(4)Based on the results of UHPC fatigue research,a theoretical calculation formula suitable for various performance indicators(cracks,deflections,strains)and fatigue cycle times of ballastless track slabs in this paper is proposed.The test results show that under the same fatigue cycle times,the stiffness of fiber composite reinforced UHPC double block ballastless track slab is significantly greater than that of fiber composite truss reinforced double block ballastless track slab,reflecting that ballastless track slab has good fatigue resistance;Using mathematical methods to fit the mathematical relationship between deflection and crack width with the number of fatigue cycles can be applied in engineering practice;The fitted fatigue life prediction curve can be used in practical engineering.