Finite Element Analysis Of UHPC Flange-narrow Width Steel Box Continuous Composite Beam’s Double Combination Effects

Compared with the traditional steel-concrete continuous composite beam,the NC(Normal Concrete)flange-narrow box beam is filled with concrete,which improves capacity of the middle support section and strengthens the structure stability.In this paper,three NC flange-narrow steel box continuous composite beams with different reinforcement ratios and shear connections have been loaded.The test shows that when the reinforcement ratio in the negative bending moment increases from 1.5% to2%,the ultimate bearing capacity increased by 12%;the shear connection is increased from 0.75 to 1,and the ultimate bearing capacity increased by 3%.However,the development of cracks on the concrete flange of the three continuous composite beams is not satisfactory.Therefore,it is proposed to use Ultra-high Performance Concrete(UHPC)flange instead of partial fill steel box continuous composite beam flange under negative moment,and use UHPC excellent tensile performance to become UHPC flange-narrow steel box double combined continuous beam structure.One is the combination of steel box and concrete flange;the other is the combination of steel box and core concrete.Using the ABAQUS finite element software,considering the relative slippage and material damage between the concrete flange and the steel box,five models were established,and a new shear resistance model was proposed.The analysis results show that the core concrete has a positive meaning in improving the bearing capacity of the section.The finite element model can accurately reflect the force characteristics of the test beam at some stages.Using this simplified stud modeling method can also accurately simulate slip trend between concrete flange and steel box beams.The cracking moment of the support section of the UHPC flange-narrow steel box continuous composite beam is significantly increased.Compared with the C40 flange continuous composite beam,when the core concrete filling amount is 0%,50%,and100%,the cracking moment is increased by 70%,159%,and 175% respectively.Taking the high cost of UHPC into account,in order to achieve good economy and applicability,the length of UHPC flange should be appropriately increased,the thickness of UHPC flange should be reduced,and the finite element model has been optimized through parameter analysis to make better results while reducing costs and improving structural performance.The stiffness formula of the support section in UHPC flange-narrow steel box continuous composite beam is derived.After considering the UHPC steel fiber bridging effect,the cracking analysis method and the other analysis method are used to calculate the moment of inertia in support section.The formulas for the cracking moment,elastic bearing capacity and short-term stiffness change of the middle bearing section are deduced.Through the verification of the finite element model,the theoretical calculation can reflect the short-term stiffness change of the section,and lay theoretical foundation for the future experimental research.