Energy dissipation and performance assessment of double damped outriggers in tall buildings under strong earthquakes

Abstract

The use of a single set of outriggers equipped with oil viscous dampers increases the damping ratio of tall buildings in about 6-10%, depending on the loading conditions. However, could this ratio be further increased by the addition of another set of outriggers? Should this additional set include dampers too? To answer these questions, several double damped outrigger configurations for tall buildings are investigated and compared with an optimally designed single damped outrigger, located at elevation 0.7 of the total building's height (h). Using free vibration, double outrigger configurations increasing damping up to a ratio equal to the single-based optimal are identified. Next, selected configurations are subjected to several levels of eight ground motions to compare their capability for avoiding damage under critical excitations. Last, a simplified economic analysis highlights the advantages of each optimal configuration in terms of cost savings. The results show that, within the boundaries of this study, combining a damped outrigger at 0.5h with a conventional outrigger at 0.7h is more effective in reducing hysteretic energy ratios and economically viable if compared with a single damped outrigger solution. Moreover, double damped outrigger configurations for tall buildings exhibit broader display of optimal combinations, which offer flexibility of design to the high-rise architecture.

Finite contact duration modeling of a Vibro-Impact Nonlinear Energy Sink to protect a civil engineering frame structure against seismic events

“…Here, a parametric study must be performed to identify reliable, but not necessarily optimal, values of the parameters governing the VI NES dynamics. In the literature on the seismic protection of civil structures, the effectiveness of a seismic device is generally expressed in terms of reducing the absolute or inter-story displacements, the acceleration or the energy injected into the structure, which is directly related to the stress level (elastic energy), or even all of these parameters together [66][67][68][69]. Here, we report the results of minimizing the cumulative elastic energy alone, that is the portion of the energy injected by the earthquake in the structure and converted into elastic deformation of the structural members of the frame.…”

A novel crosswind mitigation strategy for tall buildings using negative stiffness damped outrigger systems

“…20 In damped outrigger systems, the rigid connections between perimeter columns and outrigger ends are substituted by energy dissipation devices. 21 The concept of conventional damped outrigger (CDO) systems is first proposed by Smith and Willford 21 by applying viscous damper at outrigger ends and then this concept is extensively developed and studied by other scholars emphasizing on different aspects such as the dynamic characteristic study, [22][23][24] seismic performance study, 25,26 energy distribution analysis, 27 optimization study, 28 and replacing the viscous damper in CDO with other energy dissipation devices. [29][30][31] However, as far as the authors know, there is limited literature concerning about the crosswind performance of damped outrigger structures.…”

Performance‐based seismic design of the outrigger of a high‐rise overrun building with asymmetric vertical setback in a strong earthquake area

“…To improve structural lateral stiffness, a brace system [ 17,18 ] or outrigger [ 19,20 ] is adopted in the structure, which can improve the cooperative ability of the core tube and outer frame. At present, research emphasis of outriggers has concentrated on layout locations 21‐23 ] and damped outrigger energy dissipation effects, [ 24‐27 ] which can improve the seismic performance of high‐rise structures. However, systematic studies on reasonable design and seismic performance analyses of outriggers in different seismic level actions rarely have been reported now.…”