Research On Shear Performance Of Beam Filled With UHPC In Shear-Bending Section

Reducing the dead weight and enhancing the cracking resistance of conventional plain concrete bridges is a general problem faced by bridges in shear and bending sections.Ultra-High Performance Concrete(UHPC),with its outstanding mechanical properties and sustainability,can improve the cracking resistance of bridges.In order to take the best advantage of UHPC and to minimise or avoid its disadvantages,UHPC is cast in the shear-bending section of ordinary concrete beams where the forces are concentrated,replacing part of the heavy normal concrete,which can decrease the self-weight of the bridge and also guarantee the shear resistance of the whole beam.Therefore,this paper proposes to fill UHPC beams in the shear-bending section to solve the problem of poor crack resistance in the shear-bending section of traditional ordinary concrete beams and the high economic cost of full UHPC beams.This paper develops a theoretical model and finite element model of a shear-bend section filled part of a UHPC beam based on present theory to study the shear performance change law of the beam after filling part of the shear-bend section with UHPC,as follows:(1)Explains the properties of UHPC materials and their applications in bridge construction.Introduces the status of research on the shear strength of reinforced UHPC beams and equation for calculating the shear capacity of UHPC beams under different criteria.(2)The theory of shear bearing strength calculation for bridges is generalised,with emphasis on the terms of limit equilibrium theory and specific calculation approaches,laying the ground for the feasibility of modelling shear-bending section-filled partial UHPC beams.(3)The proportion coefficient of UHPC crack length in shear-bending section is introduced.Through the force balance equation of UHPC beam filled with shear-bending section,the normal stress and shear stress equation of concrete in shear-bending section,a unified theoretical model that can reflect the shear of ordinary concrete beam,UHPC beam and UHPC beam filled with different lengths in shear-bending section is established.(4)ANSYS was chosen to create a finite element model in order to analyse a UHPC beam filled with shear-bending sections.By defining the working situations with varying UHPC filling lengths,the finite element model was applied to a unified theoretical model of the beam subjected to shear to analyse the effect of varying UHPC filling lengths in shear-filled sections on the shear behaviour of the beam,as well as the differences in the mechanical behaviour of the beam prior to and after filling the shear-filled bend sections with UHPC,and It will also provide a guide for the design of bridges under the same requirements.