Shrinkage And Creep Effects Of Prestressed Concrete Box Girders With Corrugated Steel Webs

Prestressed concrete box-girder with corrugated steel webs is a new type of steel-prestressed concrete composite structure. The structure with a combination of significant technical and social benefits, which has the advantages of both steels tructures and concrete structures, are in inereasingly widespread applieation in recent years. Under sustained load, there will be gradual development of strain in concrete caused by creep and shrinkage, but steel don not has such characteristic. The differences between steel and conerete in long-term performance causes increases in deformation and curvature, redistribution of stress and internal actions, even redistribution of inner force in statieally indeterminate structures. In long-span composite bridges and other large complex structures, the effects caused by shrinkage and creep will be relatively more serious. So it is neeessary to consider the effects of shrinkage and creep in structural designs.This paper detailed comparison and commentary on the theoretical principle and current predictions models of shrinkage and creep. and the main characteristics and disadvantages of them are clear understood.Than researches the mechanical characteristics of composite structure which are composited by steel girder and concrete flange plates, and analyzed the section stress distribution and variation law under the effects of initial state and shrinkage and creep. Present the long-term deformation calculation methods of several common composite beams.Through the analysis of mechanical characteristics of prestressed concrete box girder with corrugated steel webs, combing the calculation method about secondary internal force result in composite structure's shrinkage and creep. Present the basic assumptions and analysis steps of finite element calculation method effect on shrinkage and creep.The factors of structure secondary force of prestressed concrete simply supported box girder of corrugated steel webs are calculated and analyzed under shrinkage and creep actors. The influence in prestressed concrete box girder of corrugated steel webs without diaphragm plates is very small. The diaphragm plates have a major effect on the section stress, and overall stress state is in the small elastic range, so it can be ignored. The creep effect calculation of prestressed concrete simply supported box girder of corrugated steel webs can be simplified:concrete top slabs and bottom slabs bear flexural moment, and corrugated steel webs bear shear. Simplified model for shrinkage and creep analysis become easy and convenient and reliable results.Finally analyze the double times internal forces of the prestressed concrete continuous box girder with corrugated steel webs. The real bridge anslysis shows that the deflection under sustained loads effects is 1.84 times about the intial deflection at the mid-span. The redistribution effects of axial force is not clear but the moment and stress have a larger change The loss of externally prestressed is larger than body prestressed. Its value is more than 10 percent for initial one after shrinkage and creep of 20 years. And the influence is larger at the early days than late.