Experimental Study On Longitudinal Negative Bending Performance Of Flat Steel Plate-UHPC Composite Bridge Deck

Ultra-high Performance Concrete(UHPC)is a new cement-based composite prepared based on the maximum density theory,which has ultra-high compressive and tensile properties,as well as ultra-strong toughness and durability.Existing engineering practice has proved that the use of ultra-high performance concrete materials in the negative moment area instead of ordinary concrete can effectively improve the crack resistance of bridge structure to solve the problem of bridge deck cracking.In recent years,many scholars have carried out research on steel-UHPC composite beam structure.However,the existing research results mostly focus on orthotropic steel plate-UHPC composite bridge deck structure,steel trough beam-UHPC composite beam structure and I-steel-UHPC composite beam structure,and there are few scholars involved in flat steel plate-UHPC composite bridge deck structure.Based on the engineering background of composite girder cable-stayed bridge,this paper carried out the following research work on the flat steel plate-UHPC composite bridge deck structure:(1)Using finite element software MIDAS CIVIL and ABAQUS,based on the general specification of highway bridge and culvert design,the overall calculation of the whole bridge and the local wheel load analysis of UHPC bridge deck are carried out according to the linear elastic theory of materials.In the process of overall force calculation,based on the bridge design specification,the safety performance of cable-stayed bridge in the construction stage and the use stage is preliminarily verified.The local analysis results of UHPC bridge deck and the overall calculation results of the whole bridge are accumulated to obtain the maximum longitudinal tensile stress at the upper edge of UHPC bridge deck in the composite beam under real bridge load.(2)Two full-scale model steel-UHPC composite bridge deck specimens were made for the static performance test of longitudinal negative bending moment.The cracking load,ultimate load,failure mode,strain distribution,load-span deflection curve and relative slip between steel plate and UHPC layer were obtained by experiments.And measure and record the crack width and position of bridge deck in the test process,get the crack germination,development and distribution of bridge deck.(3)Based on the conversion section method of linear elasticity theory,the characteristic strength of steel-UHPC composite bridge deck is obtained.The nominal cracking strength of the composite plate obtained from the theoretical calculation is compared with the maximum tensile stress in the longitudinal direction of the upper edge of UHPC layer calculated by the finite element software to determine whether the bridge deck of this new structure meets the safety requirements of the project.(4)According to the material constitutive relation,plane section assumption and section summation method of UHPC,steel bar and steel,the calculation formula of the whole process of the combined section is obtained,and the calculation program is written.The relationship between the negative bending moment of the combined section and the section strain is calculated.The curve negative bending bearing capacity,the corresponding section stress distribution and the equivalent uniform stress reduction coefficient of the tensile zone of UHPC are obtained.The calculation results are in good agreement with the tensile constitutive test results of UHPC trilinear model.