| The existing research on the influence of haunch on shear lag effects is based on single box and single chamber sections.The influence of haunch on section stiffness and local stiffening actions are considered as one variable or only one of them is considered.For this reason,this paper is the first time to study the influence of haunch on shear lag effect in a single box multi-cell CSWSB composite beam bridge.In theoretical research,the two variables are considered and analyzed separately.Finally,the dimensions of the haunch at the two positions of the side webs and the middle webs of the single box double cell section are parametrically analyzed separately.The main research results of this article are as follows:(1)For a single box double chamber corrugated steel web steel bottom plate composite box girder with equal flange thickness,taking into account the shear deformation of the web and the material difference between the upper and lower flange plates,the energy variational method is used to derive the expressions for the deflection,longitudinal stress,and shear lag coefficient of a simply supported beam at any position of the structure under concentrated and uniformly distributed load conditions.(2)The test beam model of single box double cell waveform steel web and steel bottom plate combination box girder with equal thickness of airfoil is made and loaded according to the concentrated load conditions,and the corresponding finite element model is established and verified.The results show that the trend of the three results is the same under the concentrated load at all levels,and the finite element value of the concrete wing plate at the web position is too high,which will lead to the stress concentration phenomenon leading to a large error,while the error at other positions is small and within the tolerance range;the longitudinal stress of the steel bottom plate is much larger than the longitudinal stress of the concrete wing plate under the same level of load.(3)Theoretical study on shear lag effect of single box double chamber corrugated steel web steel bottom plate composite beam bridge considering the influence of haunch.Derived the expressions for the deflection,longitudinal stress,and shear lag coefficient of a single box double chamber corrugated steel web steel bottom plate composite beam bridge under simple support conditions,taking into account both the local stiffening effect of the haunch and the variation of section stiffness.(4)Establish a finite element model of a single box double chamber corrugated steel web steel bottom plate composite box beam with haunch,compare and analyze the correctness of the theoretical expression after considering the haunch,and finally analyze the influence of the size of the outer and inner haunches of the box beam on the shear lag effect of the structure.The following conclusions are drawn from the analysis:(a)The finite element values and theoretical values of the deflection of a single box double chamber corrugated steel web steel bottom plate composite box beam under concentrated or uniformly distributed loads at all levels have the same trend,and the error between the two is relatively small,verifying the correctness of the theoretical calculation formula for deflection after considering the haunch.The influence of the haunch on the structural deflection under concentrated load conditions is greater than that under uniformly distributed load conditions.After considering the haunch,the mid span deflection under concentrated load conditions decreases by 9.22%.(b)Under concentrated load conditions,the influence of the haunch on the longitudinal stress of the concrete wing plate in the mid span section of a single box double chamber corrugated steel web steel bottom plate composite box beam is relatively large,while the influence on the longitudinal stress on the steel bottom plate is relatively small and can be ignored.The stress at most calculation points on the concrete wing plate has decreased by more than 6%,and the longitudinal stress at the edge web plate has decreased by 13.6%.Under uniformly distributed load conditions,the longitudinal stress of the structural concrete wing plate can be reduced by 5%.(c)With the size of the box chamber stem increases,the shear lag coefficient at the web position decreases.With the width of the outer haunch of the box girder increases,the shear lag coefficient at the intersection of the edge web and the top plate significantly decreases.Although the shear lag coefficient at the middle web position decreases,the reduction is relatively small.The variation of the width of the outer haunch of the box girder has a significant impact on the shear lag effect on the cantilever plate,but has a smaller impact on the shear lag effect in the inner top plate area.Compared to the haunch at the middle web,the haunch at the edge web has a greater impact on the shear lag effect.The height of the haunch has little effect on the shear lag coefficient. |
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