Experimental And Theoretical Research On Coupling Effect Of Bend-twist In Curved Double-box Girder

Curved double-box girder is a structure influenced by bend-twist effect and widening.This thesis aimed to reveal the influence pattern of curvature and widening toward curved double-box girder,also developed a method to calculate inner force of joint plate.Subjects of load effect in the research include support reaction,deflection of the girder,shear lag effect,and inner force of joint plate.Various operating conditions were established by use of numerical analysis,reinforced concrete model test and theoretical study.In numerical analysis part,a certain number of curved double-box girder and curved single-box girder with different curvature radius were created by use of the finite element software ANSYS,to exam the load effect under gravity and lane load respectively;a RC curved double-box girder model was built at ratio of 1:5 to an existing curved double-box girder,then collecting data of strains and deflections on the model under design load;in theoretical study part,developed a computational method for inner force of joint plate in curved double-box girder.Results of the study indicate as followings:1)Shorter curvature radius has more impact on double-box girder.As to the two-span continuous girder examined in the study,the ratio of inner support reaction to outer support reaction,radial stress in joint plate and longitudinal stress in base slab show exponential growth when curvature radius less than 50m(radius angle > 42°).Asymmetry shear lag effect appeared on deck slab,largest ratio of stress in the deck slab approximate to 2.2)Widening has more impact on support reactions,shear lag effect and deflection of the girder.When curvature radius turning shorter,the effect of widening increased.3)RC model test verified the accuracy of numerical study.Differential loading conditions indicate that outer unbalance load is the most unfavorable condition for girder above the other kinds of lane load.The negative support reaction under outer unbalance load reach 49% of which under gravity only.During the unbalance load test,maximum inner force of joint plate appeared at area near by loads while the other side of joint plate practically unstrained.4)The adjusted calculating method for inner force in joint plate of curved double-box girder indicate acceptable accuracy,deviation of the results computed by this method less than10% compared to numerical outcomes.