Research On Stress Of Curved Box Girder Bridge With Small Radius

Facing the safety accidents of curved box girder bridges with small radius,this paper takes Hefeng Bridge,a key project in Fuling District of Chongqing,as the research background on the basis of investigating the research status of curved bridge stress at home and abroad.The finite element software ANSYS batch processing technology and finite element software MIDAS are used to analyze the stress of the small radius curved bridge,and the function is used to fit the spatial stress distribution trend of the small radius curved bridge to obtain a regular understanding.The main research work is as follows:(1)The finite element software ANSYS is used to model Hefeng Bridge with efficient batch processing technology.Apply dead weight load to the model.Using data processing software Matlab to extract the stress of midspan section.The shear lag effect of mid-span section under constant load is also analyzed.(2)The finite element software ANSYS is used to model the curved bridge with the span of 25 m and radius of 50 m,60m,80 m and 100 m,and constant load is applied.The analysis shows that the maximum stress in the mid-span section is the place where the shear lag effect and the bending-torsion coupling effect at the outer web plate are superposed.The ratio of the maximum stress of the mid-span section of curved bridges with different radii to the maximum stress of the mid-span section of straight bridges with 25 m span is extracted respectively.The obtained ratio is fitted with a function and plotted to analyze the influence of radius on the stress of the section under dead load.(3)The bending bridge with radius of 60 m and span of 25 m,40m,50 m and 60 m is modeled by using finite element software ANSYS,and the maximum stress of the mid-span section is calculated as the superposition of shear lag effect and bending-torsion coupling effect at the outer web.Four groups of straight bridges with spans of 25 m,40m,50 m and 60 m are established respectively,and the ratio of the maximum cross-section stress between curved bridges with different spans and straight bridges with the same span is extracted respectively,and the ratio is fitted with functions and plotted into graphs.The influence of span on section stress under dead load is analyzed.(4)The finite element software ANSYS is used to establish 16 groups of models with different spans and radii for orthogonal analysis.Four groups of straight bridgeswith spans of 25 m,40m,50 m and 60 m are established.The ratio of the maximum stress of the mid-span section between the curved bridge and the straight bridge with the same span is extracted,and the ratio is fitted with functions and drawn into graphs.Orthogonal analysis of the influence of span and radius on section stress under dead load.(5)The finite element software Midas is used to model the typical three-span one-joint curved bridge model on the circular curve of Hefeng Bridge,and the maximum bending moment of the curved bridge section is calculated,which is the experimental control value.Draw the bending moment influence line of curved bridge.Use the five-axle vehicle load specified in the specification for load distribution.Manually adjust the position of the car on the bending moment influence line and calculate the bending moment,which is the calculated value of the experiment.When the difference between the calculated value and the control value is less than 5%,the correct load distribution method is obtained.(6)The distribution method calculated by Midas software is applied to ANSYS model.Symmetric and eccentric loads are applied to the side span and the middle span respectively,and four different load cases are established.Using data processing software Matlab to extract the stress of midspan section.The deflection coefficient of bending stress is introduced to measure the influence of deflection effect.The shear lag coefficient is introduced to measure the effect of shear lag.The shear lag coefficient of eccentric load is introduced to measure the superposition effect of shear lag effect and eccentric load effect under eccentric load,and the calculation and analysis are carried out respectively.(7)The finite element software ANSYS is used to model the curved bridge with the span of 25 m and radius of 50 m,60m,80 m and 100 m and apply eccentric load.The maximum stress of the mid-span section is the superposition of shear lag effect and bending-torsion coupling effect at the outer web.The ratio of the maximum stress of the mid-span section with different radii to the maximum stress of the mid-span section of the straight bridge with 25 m span is extracted respectively,and the ratio is fitted with a function and drawn into a graph to analyze the influence of radius on the stress of the section under eccentric load.(8)The bending bridge with radius of 60 m and span of 25 m,40m,50 m and 60 m is modeled by using the finite element software ANSYS,and the maximum stress of the mid-span section is calculated where the shear lag effect and bending-torsion couplingsuperposition effect are added at the outer web plate.Four groups of straight bridge models under eccentric loads with spans of 25 m,40m,50 m and 60 m are established.The ratios of the maximum stresses in mid-span sections of curved bridges with different spans and straight bridges with the same span are extracted respectively,and the ratios are fitted by functions and plotted into graphs.The influence of span on section stress under eccentric load is analyzed.(9)The finite element software ANSYS is used to establish 16 groups of models with different spans and radii for orthogonal analysis,and 4 groups of straight bridge models under eccentric loads with spans of 25 m,40m,50 m and 60 m are established.The ratio of the maximum stress of the mid-section between curved bridge and straight bridge with the same span is extracted respectively,and the function is used to fit and draw a graph.Orthogonal analysis of the influence of span and radius on section stress under eccentric load.