Evaluation of Proposed Lateral Load Pattern for Estimating Seismic Demands on RC-Tall Buildings with Shear Walls in Pushover Analysis

Abstract

The nonlinear static procedure (NSP) is becoming preferred as it favourite by virtue of its simplicity rather than nonlinear time history analysis for building evaluation and design verification. However, NSP is restricted to only a single mode response, thus this is appropriate for low-rise buildings in which the behaviour is dominated by the first vibration mode. The use of FEMA force distributions has certain flaws when high-rise buildings are evaluated; since the seismic demands are greatly underestimated especially at top stories of tall buildings. Hence, in this paper a new pushover procedure is proposed with takes into account higher mode effects. The procedure utilizes consecutive modal pushover (CMP) analyses using mode shapes obtained from a linear elastic analysis of the structure. The methodology is applied to three Reinforced Concrete frames with shear walls. It is demonstrated that the CMP procedure is able to estimate the seismic demands accurately enough and to overcome the shortcomings of FEMA load distributions when the higher mode effects are significant. Plastic hinge rotations are noticeably improved by this procedure when compared with those obtained by the MPA procedure and FEMA load distributions.