Study About Shear Lag Effects On The Different Lateral Loading Position Of Continuous Box Girder Bridge

Prestressed concrete continuous box girder bridges have many advantages including highstructural stiffness, smoothly driving, few expansion, inexpensive fee of curing, andapplicability of various spans. Box section is featured by wide flange plate and long distanceof webs, while shear-lag effect obviously exists in box section. Thus analysis of shear-lageffect in large-span prestressed concrete box-girder bridge is of great significance to preventtop and bottom slabs of box-girder bridges from transverse cracking.While most studies on shear lag effect in box girder consider loads acting symmetricallyon ribs of girder at present. For symmetrical loads which don’t act on ribs, space equivalentmethod is used to move the loads to ribs. This kind of simplified calculation for shear lageffect is convenient to shear lag effect study, but at the same time it neglects many essentialproblems, making the simplified model not matching up actual situation. Box girder shear lageffect is a complex three-dimensional problem, for the transverse acting position of load has asignificant influence on shear lag effect. On basis of precedent achievements, the writerstudies shear lag effect in box girder under loading on different transverse positions by meansof theoretical calculation, model test and finite element analysis. The main research andresults are as follows:1)Shear-lag effect in box girder is derived on the basis of energy variational principle.This paper deduces the calculation formula of shear lag effect in several kinds of box girdersunder loading on different transverse positions.2)The shear-lag coefficients of continuous beam under loading on different transversepositions are derived from integrated application of solutions limb method and energyvariational method. That is to break down the multi-span continuous box girder into severalsimply supported structures with varying depth. Displacement functions of top and bottomslabs are different. Introduce transverse acting position parameters, and consider that thetransverse loading positions of external load and support reaction is different in simplysupported system broken down from continuous beam. The influence of varying transverseacting position is then obtained. On the background of great proportion test model ofprestressed concrete continuous box-girder bridge in laboratory, the paper calculate shear-lagcoefficients of top and bottom slabs at representative sections of the test model under loadingon different transverse position.3)According to the ANSYS spatial finite element program and field loading test, theinfluence of varying transverse acting position to shear-lag effect in continuous beam isanalyzed, and that the theoretical calculation method proposed in the paper is verified correctand appropriate to apply in practical engineering. The perspective that the influence ofvarying transverse acting position to shear-lag effect in continuous beam lies on inflectionpoint of the continuous beam is proven correct. In addition, the paper proposes severalreliable research results as references for practical engineering.