Seismic behavior of eccentric reinforced concrete beam -column -slab connections.

Abstract

One of the primary goals of this research program was to develop a joint model that accounts for deterioration of shear strength and stiffness within the beam-to-column connection region. Prior experimental data did not provide enough information on the inelastic behavior of connections to establish such a model. Therefore, an experimental study was conducted, focusing on the effect of the eccentricity of spandrel beams with respect to the column, beam and column section aspect ratios, and slab participation. Three 3/4-scale exterior reinforced concrete beam-column-slab subassemblies were tested, in which the spandrel beam centerline was eccentric to the centroidal axis of the column. Lateral load was applied in two principal directions, one plane at a time, to determine the effect of prior loading on performance of the connection. Loading in the spandrel beam direction allowed a direct correlation between these three-dimensional specimens and prior testing of planar specimens without the floor system. The experimental results indicated that including the floor system significantly reduced the influence of eccentricity on the seismic behavior of the connection. When the specimens were compared to previous tests, it was observed that the damage in the connection was not as severe, the specimens had full hysteresis loops with high energy dissipation capacities, and the deterioration of joint shear stiffness and strength were delayed. Joint shear distortions contributed significantly to the total story drift for all subassemblies. Therefore, the experimental data on joint distortion was used, in conjunction with previously obtained data, to develop an analytical model of the inelastic deformations of beam-column-slab connections. The joint model was calibrated by comparing the dynamic analysis results for the specimens with experimental data. Dynamic time history analyses were performed for a sample frame building with eccentric and concentric connections. It was observed that if a deformable joint model was not included in the structural model, story drifts were underestimated significantly. Therefore, a model of the joint is necessary for accurately determining the required lateral stiffness of a reinforced concrete building subjected to earthquake ground motions.