Structural systems consisting of reinforced concrete walls/cores and concrete gravity frames are a very common structural system for moderate rise construction in regions of high seismic risk. Use of reinforced concrete or composite core walls and a steel gravity or moment frame offers an economical alternative to RC wall/core and concrete frame systems. Limited studies have been conducted to examine bearing force transfer mechanism between steel and concrete. However, fundamental issues related to cyclic performance of composite walls/cores (those with steel boundary columns) and frame-core connections are yet to be addressed. An integrated experimental and analytical program will be carried out to investigate the performance of systems with walls/cores (conventionally reinforced or with steel boundary elements) and steel gravity or moment frames. The primary objectives of this project are to: (1) conduct experimental studies of steel beam/floor system-to-core connections, (2) develop analytical modeling techniques for such connections, (3) incorporate these models into widely used inelastic structural analysis computer programs, (4) provide tools to investigate analytically complete building systems to assess the economics of using hybrid/composite systems, and (5) develop design guidelines. The research will revolve around a prototype structure which will be used to derive the test specimens, and to relate experimental data to overall structural response. The proposed research involves experimental testing of seven 1/3 -scale wall-to steel boundary columns (which may be a small erection column or a larger one), (2) amount of transverse reinforcement around the connection region, (3) contribution of composite metal decks to the stiffness and strength of the connections, particularly `shear-only` connections, and (4) the influence of beam axial load (tension or compression due to composite metal deck diaphragm action) on the performance of shear and moment connections. General analytical studies of specimen behavior will be conducted to evaluate the ability of simplified code equations to predict the strength of the subassemblages. Detailed analytical studies will also be conducted by using simplified mechanical models constructed based on equilibrium and compatibility requirements, and finite element models. These studies will assist in understanding observed specimen behavior, as well as to study additional specimen configurations not considered in the experimental phase of the research. Specific recommendations for connection design will be developed.
