| Steel-concrete composite beam is a kind of flexural member composed by concrete slab and steel connected by shear connectors. Under the long-term action of the load, the concrete in the Steel-concrete composite beam will creep and shrink, but the steel doesn't have this kind of phenomenon. The difference between the two kinds of materials will lead to the redistribution of the stress over the cross section and cause a lot of additional deformation of the structure. In large and complex structures, the consequences of shrinkage and creep is relatively more serious.This effect will greatly reduce the ultimate bearing capacity of beams and increase the burden of connectors greatly. Even lots of slip will be caused.This additional slip seriously affects the integral working performance of steel-concrete composite girder. In view of this, this thesis has made theoretical analysis on the performance of steel-concrete composite box girder under the long-term action. The main contents are as follows:(1)Based on the minimum potential energy principle, a joint differential equation, which take into account the slip and shear lag effect of box girder and can solve both deflection function and slip function under the short-term loads, is established.The expressions for deflection and slip of composite box beams under concentrated loads and uniform load are obtained.(2) Concrete creep and shrinkage are considered successfully by the use of the age adjusted effective modulus method. Based on this, a joint differential equation, which further considered the concrete creep and shrinkage about the composite box beams is established.The expressions for deflection and slip of composite box beams under uniform load are obtained.A specific example is solved then.(3)The short and long-term performance of the steel-concrete composite box girder are analyzed by the use of finite element software ANSYS.The analytical results are contrasted with the theoretical ones obtained before.The stress and deformation characteristics of the girder loads in the long-term were obtained.(4) A simulation analysis is made by further use of ANSYS in order to analyze the mechanical properties of the steel-concrete composite box girder under the long-term action. The influences of cross-sectional parameters including degree of shear connection, arrangement of the studs, cross-sectional dimensions, on the long-term performance of the steel-concrete composite box girder, are analyzed and some useful conclusions are drawn from the analysis. |
