Experimental Study On Static Performance Of Double-Block Ballastless Track Slab Reinforced By New Fiber Composite Truss

The ballastless track system in high-speed railway has been widely promoted and applied in many countries because of its low maintenance cost,good stability and long service life.However,when ZPW-2000 A frequency-shift track circuit is applied to ballastless track system,the closed circuit of steel bars in ballastless track slab and the high-frequency signal current in the internal circuit of track circuit produce electromagnetic induction,forming induced current,which makes the AC effective resistance in track impedance too large,worsens the primary parameters of track circuit,leads to the deterioration of transmission characteristics of resonant track circuit and shortens the actual transmission distance of track circuit.There are two types of closed loops in the CRTS I double-block ballastless track slab studied in this paper,including the first type of closed loop formed by the binding of vertical and horizontal mesh and the second type of closed loop formed by the welding of the truss chord.Up to now,the thermal insulation treatment method has effectively solved one of the closed circuits and ensured the structural performance.However,the other type of closed loop problem can not be effectively solved.Basalt Fiber Reinforced Polymer(BFRP)has excellent insulating properties,and is strong and durable.However,the modulus of elasticity of BFRP reinforcement is low,so the steel fiber composite bar(SFCB)is obtained by combining BFRP and steel reinforcement to improve the stiffness of FRP reinforcement.Therefore,by using these two reinforcement materials,a new fiber composite truss is innovatively proposed in this paper,and it is used to enhance the double-block ballastless track slab,so as to solve the second type of closed loop problem in the track slab.However,it is not clear whether the overall mechanical properties of the structure can be effectively guaranteed.Based on the above ideas,this paper has carried out research work on the design of the new fiber composite truss and its improvement on the static performance of the track slab.The main contents are as follows.(1)Firstly,a new type of fiber composite joist was designed,and the feasibility of the joist was verified by theoretical calculation and finite element simulation.Then the preparation of the new fiber composite trusses is carried out,and the joints of the truss are connected by winding,binding and curing.(2)The experimental study of the stability performance of the new fiber composite joist reinforced double block rail sleeper in stacking condition was carried out,and four new fiber composite joist reinforced double block rail sleepers and reinforced joist rail sleepers were prepared according to the specification requirements.This includes relevant experimental studies and theoretical calculations based on their stacking state to derive the stability performance of different double-block rail sleepers.Subsequently,it is shown that the final damage of each rail sleeper is in the form of complete "crushing" of the truss at each support and complete destruction of the nodes,and the load capacity of the four new fiber composite truss-reinforced double block rail sleepers in the stacked state can meet the actual requirements.In addition,based on the test results,the load capacity of the stacking state stability of the rail sleeper can be calculated,and the suggested stacking values for different sleepers are presented.(3)On the basis of the stability of double-block rail sleeper,the static performance of double-block ballastless rail slab is studied.One CRTS I type double-block ballastless track slab and four new fiber composite truss reinforced double-block ballastless track slabs were prepared,and the static performance of the slabs was studied by four-point loading and the related theoretical calculations were carried out.The research shows that among the five track slabs,the damage form of the steel truss double block type track slab is the lower chord reinforcement pulling off,and the damage form of the four new fiber composite truss reinforced double block type track slabs is the slant section damage of the track plate after the shoulder of the rail sleeper is crushed,and it can meet the requirements of bearing capacity and deformation performance,and the bearing capacity is improved compared with the steel truss double block type track slab.Based on the test,the ultimate bearing capacity and the crack width of the slabs are calculated and compared.(4)The finite element model of the new fiber composite truss reinforced double-block ballastless track slab was established,and the finite element simulation of its static performance was carried out to study its damage morphology,bearing capacity,strain and crack development,and the reliability of the model was verified by comparing with the experimental results.In addition,the parameter analysis is carried out by changing the type of steel mesh,the diameter of the upper chord,the diameter of the bottom chord and the diameter of the web member.