Seismic Response of 20-Story-Tall Reinforced-Concrete Special Moment-Resisting Frames Designed with Current Code Provisions

This paper investigates the two-dimensional nonlinear seismic response of four 20-story reinforced-concrete special moment-resisting frames designed according to ASCE 7-10 and ACI 318-11 code provisions. Analytical models of the buildings are subjected to a set of ground motions scaled to the smooth design spectra for the design basis earthquake (DBE) and the maximum considered earthquake (MCE) for a site located in Los Angeles, California. Significant inelastic deformations of beams are observed at both hazard levels, but the deformations at the MCE level result in large inelastic tensile strains at the base of the columns Current code provisions have been found to appreciably underestimate column axial forces and, depending on the procedure used, shear forces in columns as well. Beam growth effects were found to significantly contribute to the shear forces in the columns near the base. Methods for improving estimates of column axial and shear forces are presented.