Today’s architecture, including tall buildings, can be understood only through recognition of the dominance of pluralism. Early design of tall buildings culminated with the emergence of the International Style, which prevailed for decades. Today, however, as is true of other building types, multiple design directions are prevalent for tall buildings. This contemporary design trend has produced various building forms, such as twisted, tapered, tilted, and free forms. Among the various complex geometries employed for tall buildings, this research investigates performance-based optimum structural design solutions for twisted tall buildings. Employing twisted forms in tall buildings is a relatively new phenomenon, as are the cases with the Chicago Spire in Chicago, Shanghai Tower in Shanghai and Infinity Tower in Dubai.

Twisted tall buildings of different heights, height-to-width aspect ratios and twisted rates are designed with various structural systems. The heights of the studied buildings range from 40 to 100 stories, and the corresponding height-to-width aspect ratios range from 4.3 to 10.7. The twisted rates of the buildings range from 0.5 to 3 degrees per floor. As the twisted rate increases, the lateral stiffness of the tower tends to decrease. Compared to the conventional orthogonal towers, the lateral stiffness of twisted towers with outrigger structures is significantly low when the perimeter mega-columns are slanted in response to the twisted building form. However, the stiffness reduction of twisted towers using braced tubes and diagrids is less significant.