Research On Shear Lag Effect Of Concrete Curved Box Girder Under Vehicle Load

Curved box girder bridge is a common type of bridge structure. It not only cansatisfy the traffic connection in all directions, but also can achieve the requirementof highway alignment. The cross section forms can also satisfy the spatialdeployment of prestressed concrete structures and all kinds of pipeline and otherpublic facilities installation needs. In addition, the box section has the advantages oflight weight, strong stiffness of bending and torsional. So box girder has goodstability during construction and use age. The enough concrete area of roof andfloor can effectively meet the requirements of reinforcement. It is widely used inBridge Engineering. However, in the box girder, shear lag effect will be caused bynon-uniform distribution of shear deformation along the box girder flange platewidth, causing certain safety effect of bridges. Engineering practice has proved thatignoring shear lag effect is the main causes of serious engineering accident.Currently, the extensive research on the shear lag effect of simple box section underthe static load has undertaken, and some research achievements have beencompleted. However, due to the complexity of curved box girder cross-section formand force status, shear lag effect of curved box girder has some universal behavior,and also can aggravate the shear lag effect to some extent. The shear lag effect ofcurved box girder under dynamic load has few research results. Therefore, thesimply supported curved box girder as the research object, using large scale generalsoftware of a three dimensioned finite element ANSYS, the shear lag effect wasresearched under vehicle load. The main content of this study is as following:(1) Numerical simulation of vehicle load. Starting from the dynamic responseunder dynamic load of bridge, calculation model was put forward both on analyzingshear lag effect of curved box girder is, but also using the finite element ways. Inthe finite element analysis, the vehicle load is simplified as four point load movealong the roof and the web transfer line.(2) Parametric analysis of shear lag effect of curved box girder, Differentmodels were created of simply supported curved box girder by finite elementsoftware ANSYS. The parameters such as box girder height h, the web thickness t, the curvature radius and web spacing d were studied on the influence of shear lageffect of simply supported curved box girder. It can be drawn that height h is one ofthe biggest factors to shear lag effect of curved box girder, which summarized fromvarious parameters that affect the change rules of shear lag effect and eachparameter have influence the influence degree are different.(3) The influence of vehicle load speed to shear lag effect of curved box girderis studied. Choosing five different speed and speed gradually changed, just likefrom0m/s to8m/s, analyzing of the effect of shear lag effect by the speed change onthe curved box girder under vehicle load, the influence rules of the speed to theshear lag coefficients of curved box girder under vehicle load are get. The resultsshow that when the vehicle load is between0and6m/s, outside shear lagcoefficient increase gradually and the inside shear lag coefficient decreases; Whenvehicle load is more than6m/s, outside shear lag coefficient began to decrease andinside shear lag coefficient began to increase. Effect of speed is obvious to the shearlag effect in curved box girders.(4) Discusses the influence of vehicle load position on the hear lag effect ofcurved box girder. On the basis of the normal load position, the load moving alongthe transfer line of roof and the web, another two loads position are added. They aremoving closer to the outside and inside. And move two grid distance to the medialand lateral in the finite element model. Compared the changes of the shear lag effectof the curved box girder under3kinds of the situation of traffic load positionsmoving from the outside to the inside. Analysis shows that the impact of loadposition to shear lag effect of curved box girder is very obvious.(5) Comparative analysis of hear lag effect between curved and straight boxgirder. Parametric analysis results of curve box girder show that the height is thegreatest effect on the shear lag effect. The stress distribution at the top was studiedin1/4L,1/2L,3/4L cross-section of simply supported curved and straight box girderby three changes of height. The results show that the shear lag coefficient of straightbox girder was between inside and outside coefficient of the curved box girder atthe junction of web and roof; outside shear lag effect of curved box girder is greater than the inside shear lag effect. Stress distribution is similar to the1/4L and3/4Lroof cross section,while the stress distribution to1/2L roof cross section is verydifferent from1/4L and3/4L roof cross section’s.