Comparative Lateral Loads Performance Evaluation of a Highly Slender High-rise Building Under Different Structural Configurations

This study evaluates the lateral-load performance of a highly slender, 90-storey reinforced-concrete high-rise building under three structural configurations, focusing on serviceability, global stiffness and force demand. The building has a nominal height of 310.50 m, a plan width of 24 m and a height-to-width ratio of 12.9375. Case 1 is a reference multiple-tube structure without outriggers. Case 2 incorporates outriggers at the 30th and 60th floors. Case 3 retains the outriggers and revises the beam dimensions from 400 × 600 mm to 600 × 600 mm and column dimensions from 600 × 600 mm to 900 × 1200 mm. The configurations were analysed using ETABS, with wind and seismic actions considered in accordance with IS 875 (Part 3) and IS 1893 (Part 1), respectively. Performance was compared using maximum storey displacement, drift ratio, upper-level acceleration, modal periods, earthquake and wind base shear, overturning moment and modal response. Maximum displacement decreased from 1039.431 mm in Case 1 to 900.385 mm in Case 2 (13.38% reduction) and 615.833 mm in Case 3 (40.75% reduction). Maximum drift ratios were 0.001057, 0.000957 and 0.000784, respectively; the Case 3 reduction relative to Case 1 was 25.83%. Story 90 accelerations decreased from 0.210 m/s 2 to 0.193 m/s 2 and 0.151 m/s 2 , respectively. The fundamental period declined from 12.093 s to 11.315 s and 10.301 s, indicating increased global stiffness. Under EQX loading, base shear increased from 23,232.83 kN to 23,467.89 kN and 27,797.57 kN, while wind base shear decreased from 35,064 kN to 34,552 kN and 33,865 kN. Base overturning moment increased from 5.431 × 10 6 kN·m in Case 1 to 5.477 × 10 6 kN·m and 6.487 × 10 6 kN·m. Case 3 provided the greatest reductions in displacement, drift and acceleration, but its higher seismic base shear and overturning demand require careful verification of member and foundation capacities.