Mega-Sub Control System for Reducing Seismic Response of Tall Buildings

Abstract

This chapter evaluates the performance of the system against near-field ground motions recorded from the January 17, 1994 Northridge Earthquake and the January 17, 1995 South Hyogo Earthquake. It was surprising that many tall steel buildings were damaged in the January 17, 1994 Northridge Earthquake and the January 17, 1995 South Hyogo Earthquake in Japan. The simplest resolution for reducing and limiting the deformation and drift in lightly-damped buildings under seismic load was to augment damping devices into structural systems. However, structural characteristics common to most tall buildings, such as high rigidity of the structural system and the dominant bending deformation, resulted in technical difficulties, which prevented the application of conventional damping devices. The megasub control system taking the advantage of the megastructure configuration was proposed to overcome such difficulties. The principle of the system for reducing vibration is the same with that for conventional mass damper systems. However, the system requires no additional mass. Another additional advantage of the mega-structure configuration is its planning flexibility for sub-structures consisting of several floors in the mega-structure. The mega-sub control system examined in the chapter is a passive vibration control system that takes the advantage of the structural configuration of a mega-structure. In the system, the sub-structures contained in the mega- structure are tuned to suppress vibration energies induced by earthquake or wind load. The simplicity and effectiveness of the system make this control strategy extremely attractive for its implementation in tall and super tall buildings against seismic load.