The Study On The Mechanical Properties And Failure Mechanism Of Steel-Concrete-Steel Composite Beam

Along with the development and needs of modern science and technology,steel-concrete-steel composite structure is widely used in bridge structures、protectivestructures、ship hulls、offshore structures etc. And it has a vast range in many domains. Thereare still a lot of issues that need to be solved in field of steel-concrete-steel compositestructure, compared with traditional reinforced-concrete structure and steel-concretecomposite structure. Combining theoretical analysis and numerical simulation methods,interface mechanics characteristics and failure mechanism of steel-concrete-steel sandwichbeam are studied in this paper. The main research achievements are summarized as thefollowing:1. Using elastic and plastic theory, the formulas of elastic bending limit bearing capacityand plastic bending limit bearing capacity about steel-concrete-steel composite structure isestablished, and was analysed the influencing factor about plastic bending limit bearingcapacity. The results indicated that the strength and thickness of the steel panel had a greateffect on the plastic bending limit bearing capacity and had no effect on the concrete strength.2. In view of the actual stress and deformation of the steel-concrete-steel compositestructure, the micro section analysis model of the composite structure was established. Byanalyzing the force balance and deformation coordination of the composite beam, thedifferential equation about interface slip is gained, interface slip and slipping straincalculation formula of simply supported composite beam by the mid-span concentrated load、two load symmetry、uniformly distributed load and any concentrated load were derived. Thesedepth studies on the system may conduce to the mechanical property of the SCS compositebeam.3. The major parameter of interface slip and slipping strain distribution was analysed.The results indicated that shear connection degrees have a great effect on the interface slipand slipping strain, as shear connection degrees increased, interface slip and slipping strain isreduced. Steel content have a big effect on ssand εs, less influence on stand εt, as steel contentincreased, interface slip and slipping strain is increased. The strength classes of concrete had a small effect on ssand εs, almost no influence on stand εt, as strength classes of concreteincreased, interface slip and slipping strain is a little decreased.4. The formula of axial force and curvature of section and deflection and cross-sectionalstress was established considering the interface slip.And the influence of the interface slip onaxial force, section curvature, deflection and section stress was analysed. The studies show,that axial force Nswould increase, section curvature and deflection would increase along withthe interface slip decreasing. The influence of the interface slip on section stress of away fromthe border face was smaller，and the influence on section stress of closer the border face wasgreat.5. The numerical model was established about FRP reinforced concrete beam, theconcrete beam with complex crack and steel-concrete-steel composite beam, and used thenumerical simulation to research the the failure process. Numerical simulation results had agood agreement with experimental results. And then similar numerical model ofsteel-concrete-steel composite beam considering of interface influence was established usingthis method. The failure mechanism of the composite beams was analyzed under the differentstrength of interface. The studies show, that the failure form of the composite beams mainlyfor the debonding failure between steel plate and concrete leading to by interface failure, andbonding failure between steel plate and concrete leading to by many crack in the inferiorborder of concrete. As the strength of interface increased, the ultimate bearing capacity of thecomposite beams is increased, and ductility was better.