Study Of Shear Resistance Of Partially Filled Narrow Steel Box-UHPC Composite Beam

In recent years,with the rapid development of China’s economy,the traffic load has increased significantly,and the development of road and bridge engineering technology is particularly important to ensure the country’s rapid economic growth.The traditional steel-concrete combination girders have problems such as flange cracking under negative bending moment,based on the partially filled narrow steel box-concrete combination girders,the partially filled narrow steel box-UHPC combination girders are proposed.The stability,stiffness and shear capacity of the combined girder are improved by using UIHPC-NC flange.In this paper,the shear resistance of partially filled narrow steel box-UHPC composite beams is investigated by means of experimental and theoretical analysis and numerical analysis to provide a basis for structural shear resistance design.The main research work and results are as follows:(1)Based on previous research results,a partially filled narrow steel box-UHPC composite beam system was proposed,six test beams were designed and fabricated with UHPC flange thickness,steel fibre admixture and height of filled concrete as the main parameters,static loading tests were carried out,the loading characteristics,crack development characteristics and damage patterns of the test beams were observed throughout the loading process,the mid-span load-deflection curve,section strain curve The test results showed that the addition of steel fibres could effectively inhibit the cracking of the flange,and the maximum crack width of the specimen was reduced from 1.06 mm to 0.92 mm when the steel fibre admixture was increased from 0 to 2%,and the deformation capacity was enhanced by 23.61%.The load carrying capacity of SUCB-1(1/2 UHPC flange)and SUCB-4(full UHPC flange)was increased by 18.2% and 27.3% respectively,and the deformation capacity was increased by 38.02% and 41.2% respectively;the partial filling of the steel beam with concrete effectively suppressed the buckling of the steel beam web and improved the stability and cross-sectional stiffness of the combined beam,compared to specimen SUCB-5.Compared to specimen SUCB-5,the load carrying capacity of specimen SUCB-1(semi-filled)and specimen SUCB-6(fully filled)increased by 65% and 77.22% respectively,while the deformation capacity increased by 55.83% and 24.71% respectively.(2)The finite element model of the test beam was established using ABAQUS software,and the applicability of the finite element model to the partially filled narrow steel box-UHPC composite beam was verified by comparing the numerical analysis results with the test results.The main factors affecting the shear performance of the specimens were analysed to provide a theoretical basis for the design method of the shear load capacity of partially filled narrow steel box-UHPC composite beams.(3)A comprehensive comparison of the shear load capacity design methods of the US and European codes;based on the test results and FEM analysis results,the shear load capacity calculation formulae for partially filled narrow steel box-UHPC composite beams are derived based on the codes and relevant literature,which take into account the contributions of the UHPC-NC flange,steel box beam and filled concrete to the shear load capacity of the test beam.