Directional displacement demand in tall RC buildings under pulse-like ground motions

Abstract

Ground motion directionality under pulse-like excitation significantly affects structural demand in tall buildings, but its interaction with lateral force-resisting systems is not fully quantified. This study investigates the orientation-dependent response of a rectangular reinforced concrete building subjected to pulse-like motions from the 2023 Turkey earthquake. Four structural configurations are investigated: a regular moment-resisting frame, a shear wall system, a fluid viscous damper system, and a combined system. Bidirectional ground motions are rotated from 0 to 180 degrees and evaluated using time-history analysis with the Fast Nonlinear Analysis procedure. Since peak responses in orthogonal directions do not occur simultaneously, the governing roof displacement at each orientation is defined as the maximum absolute peak response in the principal directions. Dispersion, normalization, and exceedance-based performance indices are used to quantify directional variability and system effectiveness. The mean DSIe values are 0.212, 0.188, 0.318, and 0.313 for the regular, fluid viscous damper, shear wall, and combined configurations, respectively, with the FVD configuration reducing mean directional dispersion by approximately 11.3% relative to the regular frame. The mean NSER of the FVD configuration is 0.858, indicating an overall reduction in roof displacement, although a maximum NSER of 1.336 occurs for GM 4631 at 6°. The dominant pulse periods exceed the fundamental periods of all configurations, indicating long-period pulse characteristics relative to the structural periods. The findings indicate that orientation-dependent pulse-structure interaction can change the relative effectiveness of the investigated stiffness- and damping-based systems, emphasizing orientation-dependent evaluation in performance-based seismic design.