Comparative Study Of NC Flange And UHPC Flange Concrete Partially Filled Narrow Steel Box Continuous Composite Beam

The negative moment zone of traditional steel box-concrete continuous composite beams is in an unfavorable stress state.Based on the partially filled concrete steel box continuous beam,this paper further proposes the UHPC partially filled concrete narrow steel box continuous composite beam.This structure uses Ultra-high Performance Concrete(UHPC)instead of ordinary concrete panels in the negative moment zone to improve the problem of premature cracking of the concrete panels in the negative moment zone and exit from work,further improving the overall rigidity of the structure And load capacity in the negative bending moment zone.In this paper,relying on the National Natural Science Foundation of China,based on the research group’s existing NC partially filled concrete narrow steel box continuous composite beam specimens,finite element analysis of UHPC partially filled concrete narrow steel box continuous composite beam is carried out.(1)Through experimental research,the experimental phenomena of concrete wing plate cracking,crack development process,local buckling and deflection deformation of steel box beam during the experiment of NC partially filled concrete-steel box continuous composite beam are described.The reasons for its occurrence were analyzed,and test results such as the wing plate crack width-load relationship curve,load-midspan deflection relationship curve,and section height-strain relationship curve were obtained.(2)The ultimate bearing capacity of NC composite beams and UHPC composite beams is calculated through theoretical analysis.The results show that the ultimate bearing capacity of UHPC composite beams is about 12% higher than that of NC composite beams.Establish a finite element model of NC composite beam and compare and analyze the measured values.It is found that the force process of the two is basically the same,indicating that the model established in this paper can truly reflect the actual force state and characteristics of the NC composite beam during the test.(3)On the basis of the NC composite beam model,replace the NC panel in the negative moment area with UHPC to establish a UHPC partially filled concrete-steel box continuous composite beam model,and draw conclusions by simulating and analyzing the UHPC composite beam.The results show that the ultimate bearing capacity of the latter is about 14% higher than that of the former,which is 2% different from the theoretical calculation results.The tensile damage area of the panel in the negative bending moment area is about 13% smaller than that of the NSC composite beam.(4)By changing the UHPC wing plate thickness and longitudinal configuration of the UHPC composite beam finite element model,the UHPC composite beam section is optimized.Finally,considering the three factors of mechanical performance,convenient construction and economy,it is recommended that the optimal thickness of UHPC panel layout is 0.65H～0.75 H of the entire concrete flange edge,and the best longitudinal width is 0.3L～0.33 of the span.L.