Experiment Study On The Steel –concrete-steel Composite Beam Subjected To Cyclic Lateral Loading

Steel-concrete-steel composite structure is a relatively new structure form which is widely used in bridge structures, building structures, protective structures, oil storage tank, explosion-proof engineering, ship engineering and nuclear power engineering etc. This dissertation focuses on steel-concrete-steel composite structure with shear studs and tie bars which is utilized in safety-related nuclear facilities. The in-plane behavior of steel-concrete-steel composite walls is thoroughly investigated by many researchers while the out-of-plane behavior remains unknown. And there is not much literature about steel-concrete-steel composite beams. The quasi-static test of a steel-concrete-steel composite beam has been conducted to investigate its seismic behavior in order to provide some design recommendations for safety-related nuclear facilities. The main works of this dissertation are summarized as follows:(1)A literatural research on the shear resistance and load-slip curves of stud shear connectors has been made in order to specify the design strength of stud shear connectors in steel-concrete-steel composite beams. Baesd on plasticity and limit analysis theory, the formulas for determining the ultimate resistance of steel-concrete-steel composite beams are presented. In order to achieve full shear connection between steel-plate and concrete and avoid the local buckling of steel-plate, the amount and interval of stud shear connectors and tie bars must be designed carefully based on plasticity and limit analysis theory a nd ductile failure concept. The shear connectors should also satisfy other detailing requirements.(2)A quasi-static experiment has been conducted to study the failure process of the steel-concrete-steel composite beam subjected to cyclic lateral loading, in which the load-displacement hysteretic curve, skeleton curves, the stress and strain distribution law and the law of the interfacial slip are investigated and the energy dissipation capacity and ductility, equivalent stiffness of the specimen has been analyzed. It shows that the specimen’s load-displacement hysteretic curves are very narrow due to shear failure of the shear connectors. There is no obvious yield point on the load-displacement hysteretic curves and the ultimate displacement of the specimen is very small, which indicates poor ductility.(3)The seismic behaviour of the steel-concrete-steel beam specimen is simulated with the finite element software ABAQUS. The steel-plate, concrete and shear connectors are simulated through choosing suitable units, the interaction between the various parts can be considered, and the longitudinal shear force transfer between steel-plate and concrete is simulated with nonlinear spring elements. The validity of the finite element model has been verified on the f orce mechanism and stress transformation of the test specimen. Finite element calculation results show that the shear force of the shear connectors along the specimen length distributes uniformly. The shear force on stud shear connectors increases more rapidly than that on tie bars with increasing lateral load applied on the beam specimen. The shear connectors failed in brittle fracture due to lack of welding strength, and then the tie bars simultaneously failed in shear fracture due to additional stress caused by failure of stud shear connectors. At last, the interfacial connection between steel-plate and concrete lost the bearing capacity and concrete failed in brittle fracture, resulting in specimen lost the bearing capacity and failed in brittle.