Study On Mechanical Behavior Of Steel-concrete Composite Beam Bridge Considering Interface Slip

Composite beam, which comprises a steel girder and a reinforced concrete slabinterconnected by shear connectors, has both advantages of steel structure and concretestructure. Although it has been widely investigated at home and abroad, many problems stillneed to be worked over in design and in practice. In this thesis, studies have been carried onabout the relative tangential displacement (slip) between the steel girder and the concrete slab.New methods have been proposed and been used to analysis the effects of the slip onmechanical behavior of the composite bridge. The main research works are as follows:According to the mechanical behavior, shear connector has been considered as a Winklerfoundation with an assumption of the linear relationship between the stiffness and the depth.A displacement differential equation has been set up and solved by the power seriesexpansion. An analytic method for calculating the slip stiffness of shear connector has beenproposed, and a constitutive relation between load and slip has also been established.The differential governing equations of composite beam considering the slip effect hasbeen present based on minimum potential energy and Goodman’s hypothesis. Freelysupported composite beam under uniform load concentrated load has been studiedrespectively, and the deflection expressions are obtained.A structural modeling methodology was presented. A segment of the composite beamwas divided into several parts, which include concrete slabs, steel girders and shearconnectors. Each part is regarded as a sub-element. The stiffness matrixes of everysub-element were obtained via the variation method respectively and then assembled into asuper-element with the compatibility of deformation. Through the secondary development ofUPFs, the user element is realized on the finite element software ANSYS.Two scale model tests have been designed to verify the methods proposed in this thesis.A three spans composite beam bridge was taken as the archetype. The first test included twocomposite beam segment models with the same scale of1:2and aimed at the stressdistribution and the relative tangential displacement of the composite beam with the differentkind of connectors. Common shear connectors were used in one model while U-steelconnectors were used in the other. Two observations as follows were found:(1) two modelsshare the same collapse mode but are different in the value of the vertical collapse load, themodel with U-steel connectors has bigger the vertical collapse load than the other;(2) whenthe model borne the horizontal force, the test slip curves and calculating curves whichobtained by using the method proposed in this thesis have the same tendency although they have some different values. After proposing a method for calculating the shrinkage and creepeffect of composite beam, The second test has been carried on to validate it based on a scalemodel which is1:8of the archetype. It was found from the test that the method is suitable forthe composite beam.Based on the achievements in this thesis, the constitutive relation between load and slipand the super-element of composite beam, Hedong bridge and Jiujiang new bridge werestudied in detail to uncover the effect of slip stiffness on mechanical behavior and ultimatebearing capacity under the common load.