ABSTRACT
This paper investigates structural performance of outrigger systems employed for twisted, tilted and tapered tall buildings. Compared to core shear wall structures, outrigger structures carry wind-induced overturning moments more efficiently with greater structural depth by connecting perimeter mega-columns to stiff building cores through outrigger trusses. The outrigger system’s lateral load carrying mechanism is conceptually explained in Figure 1. The overturning moment (Mo) caused by wind loads (W) is reduced due to the counteracting moment (Mc) provided by the mega-columns connected to the building core through the outrigger trusses. The counteracting moment can be expressed as
(1)
A is sectional area of mega-columns; E is modulus of elasticity of steel, assuming steel is used; Fis curvature. Since the modulus of elasticity of steel is almost constant regardless of its strength, the outrigger’s bending rigidity is a function of the square of the building width and sectional area of the mega-columns.
