Abstract
SummaryThe 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.
Highlights
Outrigger systems consist of a series of cantilever truss beams or shear walls connecting the building core with the perimeter columns
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)
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 both more effective in reduce hysteretic energy ratios under strong earthquakes and economically viable if compared with a single damped outrigger solution
Summary
Outrigger systems consist of a series of cantilever truss beams or shear walls connecting the building core with the perimeter columns. Dampers have been introduced between the perimeter columns and the outriggers resulting in an increase in the overall damping of the building.[1] A few implementations of this system, called damped outrigger, have been reported elsewhere.[2,3,4] Both practice and research have shown that an optimal outrigger location and damping coefficient of the dampers largely influence the increase of the damping ratio.[1,3,4,5,6,7,8] Under an optimal configuration, damped outriggers are meant to absorb the excessive earthquake energy that would otherwise cause damage in the structure. Under large or severe earthquake‐induced motion, some plastic hinges or failures may be produced in the host structure before the dampers are able to dissipate the total input energy
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