Study on performance of various installation makeups of damped outrigger systems

The frame-core-tube system is one of the most widely used structural configurations in tall buildings. To minimize lateral displacements in such structures, a novel energy dissipation mechanism known as the damped outrigger system has been developed. Traditionally, vertical viscous dampers are installed in parallel between the outrigger trusses and peripheral columns. This study proposes three alternative installation configurations for damped outrigger systems and investigates their performance and efficiency through time-domain and frequency-domain analyses. The stiffness matrix for each configuration of the damped outrigger system is derived. By incorporating this matrix into a dynamic stiffness matrix, the dynamic characteristics of the system are determined based on Bernoulli-Euler beam theory. The study explores the impact of various parameters, including the stiffness ratio of the core to perimeter columns, column stiffness ratios, optimal placement of damped outriggers, and the optimal damping coefficient. 3D surface plots are presented to illustrate the modal damping ratio as a function of damping and outrigger location, enabling the identification of optimal parameters for each mode. The dynamic characteristics and structural response are further analyzed using an augmented state-space equation. Numerical simulations validate the optimal parameters derived from the proposed methodology. This approach provides a comprehensive framework for the preliminary design of tall buildings with damped outrigger systems.