Nowadays, in modern tall buildings, lateral loads induced by wind or earthquake forces are often resisted by a
system of multi-outriggers. An outrigger is a stiff beam that connects the shear walls to exterior columns. When
the structure is subjected to lateral forces, the outrigger and the columns resist the rotation of the core and thus
significantly reduce the lateral deflection and base moment, which would have arisen in a free core. During the
last three decades, numerous studies have been carried out on the analysis and behavior of outrigger structures.
But this question is remained that how many outriggers system is needed in tall buildings.