SEISMIC RESISTANCE OF REINFORCED-CONCRETE FRAME STRUCTURES DESIGNED ONLY FOR GRAVITY LOADS - EXPERIMENTAL PERFORMANCE OF SUBASSEMBLAGES

The behavior of gravity load-designed reinforced concrete members unde r simulated seismic loading was investigated experimentally. Four colu mn specimens, loaded with low and high levels of axial forces, with an d without lap splices, representing interior and exterior columns at f loor slab and beam soffit levels, were examined under reversed cyclic loading at increasing drift amplitudes until failure. The failure of a ll columns was flexurally dominated, resulting from either: concrete c rushing and buckling of the longitudinal steel in the case of columns with high axial load; or from low-cycle fatigue of the longitudinal ba rs in columns with low levels of axial load AIL columns were capable o f sustaining at Least two cycles of loading at a 4 percent drift angle . In addition, two specimens at one-third scale that model typical ext erior and interior slab-beam-column subassemblages, of a prototype bui lding frame designed and detailed only for gravity loads, were subject ed to axial load and reversed cyclic lateral displacements. The exteri or subassemblage experienced a weak beam-strong column failure mechani sm, whereas the interior; subassemblage developed a weak column-strong beam mechanism. This paper presents important experimental results, a nd attempts to model analytically the seismic behavior and parameters that govern the seismic response. Conclusions are drawn on how individ ual detailing deficiencies can affect the seismic response and failure mechanism of a structural frame as a whole.