Test And Finite Element Analysis On Flexural Performance Of UHPC-NC Composite Beam Bridge

In the medium and small span bridges,concrete bridges are limited by the concrete materials themselves.The structure is self-reliant and the forms are relatively simple.At the same time,the problems of the concrete bridges such as easily cracking and lowdurability are ubiquity.The steel bridges generally suffer from rust,fatigue and other diseases,so the maintenance costs are high in the later period,and most of opeartions are cast-in-place,and the assembly rate needs to be improved.The explorations of beautiful shapes,convenient construction,high degree of assembly,strong durability,economic and environmental protection,low maintenance costs,and good economic performance over the entire life cycle,the new structural form suitable for medium and small-span bridges have become a major challenge for the engineering community.This paper proposes a new type of assembled doubleI-shaped UHPC-NC composite beam structure,and checks calculation of the current specification and French UHPC specification,and establishes a finite element model for simulation analysis.The main work and conclusions of this paper are as follows:(1)According to the project,a 30m-span UHPC-NC composite bridge scheme was proposed.Compared with the traditional C50 prestressed T-beam bridge,the UHPC-NC composite bridge only has 70.7% of its weight per square meter of conventional prestressed T-beam.This paper also carried out a preliminary design calculation of the relying on the project,mainly with reference to the current domestic relevant standards and the French UHPC specification,checking the flexural load carrying capacity,shear carrying capacity,and the crack width under normal service limit conditions.The verification results show that the indicators meet the design requirements.(2)A 1:2 scale model was designed and tested for bending performance.The results show that the proposed UHPC-NC composite beam flexural bearing capacity meets the practical engineering requirements.(3)Based on ABAQUS nonlinear finite element software,a simulation model of the scale model was established.The calculation results were compared with the experimental results.The results show that the finite element model has certain accuracy and applicability.And based on this model,the effects of reinforcement ratio,reinforcement yield strength,UHPC tensile strength,compressive strength and the ordinary cast-in-place concrete grades on the bending performance of UHPC-NC composite structure were analyzed.The results show that: increasing the reinforcement ratio of the main beam,the yield strength of the steel bar and the UHPC tensile strength can increase the bearing capacity of the structure.Besides increasing the reinforcement ratio of the main beam and the UHPC tensile strength can also increase the post-cracking stiffness of the structure.The compressive strength of UHPC basically has no effect on the structural stress.Increasing the strength of cast-in-place bridge panels can improve the structural stiffness after cracking,but the impact is not significant.(4)The finite element model of the UHPC-NC composite beam considered the secondary force was established,and the influence of the secondary force on the bending performance of the composite beam was analyzed.The calculation results show that the bearing capacity of the two-stage composite beam is not lower than that of the one-stage composite beam,but the difference is not significant;the effect of material parameters on the mechanical behavior of a two-stage composite beam is basically the same as that of a composite beam subjected to a stage of force.