Seismic behavior of composite steel frame-reinforced concrete infill wall structural system

A composite steel frame-reinforced concrete infill wall, in which the steel and concrete components work integrally through mechanical connectors, offers significant advantages as an earthquake-resistant structural system for buildings located within regions subjected to earthquakes. This project was aimed at the investigation of the seismic behavior of the composite steel frame-reinforced concrete infill wall structural system through a combined experimental and analytical research program.; The primary part of this research was conducting a cyclic loading test on one two-story, one-bay specimen, which represented the bottom two stories of a six-story prototype structure at approximately one-third scale. Partially-restrained (PR) connections were used to join the wide flange steel columns and beams. The infill was cast using regular concrete. Confined headed studs were used as the interface connectors.; The test showed that this system provided sufficient strength to resist the design lateral loads and ample stiffness to control system drift. Adequate redundancy was provided to the system by alternate load paths, such as shear stud-infill interaction and truss action due to steel frame-infill interaction. At the design lateral load level, 80–90% of the lateral shear force was transferred from the steel frame to the infill through the headed studs, and approximately 80% of the overturning moment was carried by the steel columns. The ultimate strength of the specimen was induced by crushing of the concrete in the comers, yielding and fracture of the studs, and formation of plastic hinges in the PR connections. Adequate confining reinforcement was critical to enhance the strength and ductility of the studs in the infill panels. The failure of the studs was controlled by low cycle fatigue.; The second part of this thesis includes a description of linear elastic finite element analysis for use in design and a plastic mechanism analysis procedure to verify lateral load strength. Design recommendations are proposed to ensure the development of the desirable failure mode.