Study On The Long-term Performance Of Steel-concrete Composite Beams Under Repeated Loading

Steel-concrete composite beams have advantages of both steel and concrete structures, so it has been increasingly appeared in construction and bridge engineering application. Steel and concrete composite beam is combined by two kind of different materials, so it will receive the constraints of steel due to the shrinkage and creep in concrete, which will cause the redistribution of stress over the cross section. Under actual operating engineering, however, many structures are subjected to dynamic loading in addition to static loading. Dynamic loading are often cyclic in nature, such as traffic loads and so on. Creep would be accelerated under cyclic loading particularly of many repetitions. Therefore, this thesis has made theoretical analysis on the behaviors of steel-concrete composite beam under long-term repeated loading. The main contents are as follows:(1) BP model is adopted to set up a long-term deformation theory calculation model of the steel-concrete composite beam under long-term repeated loading. And a specific example is solved then. Parametric studies are carried out to analyse the effects of various parameters including the relative humidity, mix proportions, concrete age at loading and loading frequency.(2) The finite element model of the steel-concrete composite beam is builded by the use of finite element software ANSYS. The analytical results are contrasted with the theoretical ones obtained before. The deformation and stress characteristics of the composite beam under long-term repeated loading were obtained.(3) A simulation analysis is made by further use of ANSYS in order to analyze the mechanical properties of the steel-concrete composite beam under the long-term action. Parametric studies are carried out to analyse the effects of various parameters including the diameter of stud, strength of concrete, thickness of concrete flange, width of concrete flange, web height of steel and flange width of steel.