Study On Shear Performance Of Steel-concrete-steel Sandwich Composite Beam-slab Members

At present,reinforced concrete guardrails and beam-column guardrails are most commonly used in bridge guardrails.Reinforced concrete guardrails have high stiffness,and under normal impacts such as vehicles,cracking and spalling usually occur.The ability to cushion the vehicle's kinetic energy is small,and concrete debris splashing poses a huge safety hazard.Beam-column guardrails consist of multiple parallel steel pipes with low protection level,which is not enough to withstand vehicle impact.This paper proposes that a double-layer steel-concrete-steel(SCS)sandwich composite structure can make full use of the superior tensile properties of steel and the compressive properties of concrete.Enough,can also rely on the tensile film effect of the steel plate to withstand greater deformation,dissipate most of the impact energy.However,there are few studies on the failure mechanism of SCS sandwich composite structure,and no unified theory and design method have been formed.Through experiments and theoretical methods,this paper studies the failure mechanism of the proposed SCS sandwich composite beam and composite plate member under static concentrated load.The details are as follows:(1)Experimental study on the shear resistance of SCS sandwich composite beam(two-dimensional force).The effects of shear-span ratio,steel plate ratio,shear connector spacing and type on the failure mode and shear performance of SCS sandwich composite beams were analyzed,and the failure mechanism considering the effects of bond slip effect was revealed.The test results show that the bond slip changes the failure mode of the composite beam and reduces its shear strength;by reducing the distance between the shear connectors,the composite degree ?b of the steel plate and concrete is increased,and the composite effect between the steel plate and concrete is enhanced.Reduce the amount of bond slip between the steel plate and concrete,and the shear contribution of the steel plate is improved.(2)Experimental study on the punching resistance of SCS sandwich composite slab(three-dimensional force).Fill ULCC as the core material at the material level,its apparent density is 1387g/cm3,and the compressive strength of the cube is 52.6MPa,and increase the number of core material layers at the structural level.The effects of core material height,corematerial layers,steel plate thickness,type and spacing of shear connectors,area of loading area on the ultimate bearing capacity and failure mode of SCS sandwich slab are discussed in order to study its punching failure mechanism.The test results show that the addition of fibers increases the ULCC tensile strength and delays the crack development;the core material blanking diagonal crack ? ranges from 45o to 67o;the increase in the number of core material layers reduces ?,and more core materials are fully utilized to make the SCS sandwich composite slab's punching bearing capacity has increased significantly.(3)Based on the analysis of test results and existing design codes,the two-dimensional shear bearing capacity model of SCS sandwich composite beam and the three-dimensional punching bearing capacity model of SCS sandwich composite slab are proposed respectively.The calculated model prediction values and The test values agree well.