The Study Of Transverse Prestressing’s Framing Effect Of The Prestressed Concrete Box Girder Bridge

Variable cross-section of prestressed concrete box girder bridge with the well capacity of carrying on structural press, has become one of the most commonly used bridge structure, but the phenomenon of box girder top plate with longitudinal cracking is commonly found. Although the transverse prestressed steel bar is set, longitudinal cracks in box girder top plate still produce. This shows that the set of transverse prestressed did not achieve the designed expectation results. Caused by transverse prestressed bars in top plate tensioned, then the deformation of top plate happens. Because the box girder is statically indeterminate structure, the web will offset a part of the transverse prestress. It is that the framing effect. Top plate has been used to support load as an important member of the box girder. Therefore, researching on transverse prestressing suffer the effects of the web framing effect weakening, which is great significant in preventing longitudinal cracks in top plate.This paper mainly aimed at the influence of the framing effect on the top plate transverse force. The solid model establishes by a typical variable cross-section cantilever box girder bridge as the engineering background, are analyzed with finite element analysis software ANSYS. By simulation of tensioning transverse prestressing steel bar in top plate to study the distribution rules of transverse stress in top plate and the effects of framing effect in the top plate.At the same time, three methods of layout in transverse prestressing steel bar is studied the weakening effect of the web framing effect. By comparison of the analytic results, we can obtain the rules of framing effect weaken transverse stress in top plate.Finally, In Wuyang River Bridge as background to establish the real bridge model for finite element analysis, the study only in the eccentric prestressing force, under the action of the self weight of structure roof transverse force distribution,and the vehicle load under the joint action of roof transverse force distribution. The roof of the Transverse Prestress reserve stress value of longitudinal cracks can resist the roof. Some suggestions about the layout and design of transverse prestressing steel bar...