Behavior of beam-column connections under axial column tension

Recent analytical studies have shown that reduced column compression and even tension may be experienced by intermediate stories of medium to high-rise reinforced concrete (RC) structures. This is a consequence of high overturning moments coexisting with vertical ground motion. In recognition of such observations, the present study was initiated to investigate the seismic performance of interior beam-column subassemblages under reduced column compression or net tension. A state-of-the-art synchronized shake-table facility was used to test a total of six ordinary and marginal high-strength RC interior subassemblages. A nonconventional design approach was adopted to ensure pure panel-zone (PZ) shear failure, hence a realistic estimate of joint shear strength will ensue. Results indicated loss of shear capacity and increase in deformability when compression column load is markedly reduced or tension is experienced. Findings of this investigation are most useful in providing necessary information about the effect of axial tension on the PZ shear capacity, the joint confinement efficiency, and the overall structural stability in areas of potential high vertical earthquake excitations.