Theoretical Analysis And Experimental Study On The Ultra-high Performance Concrete Shaped Thin Plate Stairs

Combined with the current development trend of lightweight coMPonents of domestic and foreign fabricated coMPonents,ultra-high performance concrete materials are applied to the stair structure,and a new shaped thin-plate staircase is proposed.CoMPared with the traditional stairs,this profiled thin-plate staircase has the lightweight and high-strength characteristics.CoMPared with the traditional beam staircase,a new type of sheet L-shaped stepped staircase is fabricated with an ultra-high performance concrete.A series of bending experiments and finite element nonlinear analysis were carried out to study of the bending properties of the as-proposed thin L-shaped stepped stairway,where the main parameters included the reinforcement and steel fiber.The influence of the parameters on the failure modes of the stair were analyzed as well.A method is proposed to obtain the load bearing capacity of the as-proposed sheet L-shaped stepped staircase.The experimental results show that the thin-plate L-shaped step board stairs should be arranged with steel bars,and that the length-diameter ratio of the steel fiber to be incorporated should be larger than 100;in the normal use stage,the stair steel bars are not yielding,and the load bearing capacity obtained through the experiments is much larger than that according to the load standard.Under the limit load,the deflection of the stairs meets the requirements of the mid-span deflection limit of the normal use limit of the stairs.In the normal use phase,the average ratio of the calculated load carrying capacity to the experimental one is 0.94,and the mean square error is 0.031,which indicates that the proposed bearing capacity calculation method can accurately estimate the bearing capacity.In addition,the nonlinear analysis results based on ABAQUS agree well with the experimental ones,which verifies the rationality of the finite element model.Based on the finite element model,three-point bending was carried out to study the bending properties of the tread staircase with a width of 2400 mm.The results show that the tread staircase with a width of 2400 mm can meet the requirements of load bearing capacity and deflection limit even under the normal use limit state.The bearing capacity and deformation performance of the stairs under normal service limit conditions were studied by means of theoretical derivation,experiments and finite element analysis.For the derivation of deflection theory,the shaped thin-plate staircase is equivalent to a rigid rod,and the two ends of the stair are hingedly connected.Through the simultaneous equilibrium equation,the formula was derived for calculating the internal force and deflection of the stair.Under the ultimate load,the theoretical maximum calculated deflection of the stair is 6.858 mm,which is smaller than the normal limit of 8.64 mm and meets the deflection limit.The experimental results show that under the normal use limit state,the special-shaped thin-plate stairs meet the requirements of load bearing capacity and deflection limit;in the process of stair stress,the load shared by the steel bars is small,and the effect of steel bars on the bearing capacity of the stairs can be neglected.However,the steel frame must be arranged.CoMPared with the theoretical,experimental and finite element analysis results of 400 mm wide-profile thin-plate stairs,the rationality of the finite element model of the stairs is verified.The model is used to nonlinearly analyze the prototype of the stair structure,and the bearing capacity and deformation performance of the prototype stair are obtained.The finite element results show that under the normal use limit state,the prototype plate of the profiled plate meets the requirements of bearing capacity and deflection limit.Based on the coMPrehensive theoretical,experimental and finite element results,the proposed special-shaped thin-plate stairs can meet the requirements of bearing capacity,deflection limit and stair structure deformation under the normal use limit state,.This study provides some experimental and theoretical support for the application of ultra-high performance concrete shaped plate stairs.