Selecting a particular structural system for tall building design involves many complex factors such as availability of resources including material and labor, architectural aesthetics, spatial configurations, and structural efficiency. Among these various factors, this study investigates the lateral stiffness-based comparative structural efficiency between today’s prevalent structural systems for tall buildings such as variously configured braced tubes, diagrids and outrigger systems.

The two most important design requirements for structural design are strength and stiffness, and for a very tall building with a large height-to-width aspect ratio, the stiffness constraint generally governs the design. Braced tubes, diagrids and outrigger structures are optimally designed for tall buildings of various heights and height-to-width aspect ratios. Stiffness-based design methodologies are used to meet the design requirements. The heights of the studied buildings range from 40 to 100 stories. Other important structural geometric configurations, such as the angle of diagonals for braced tubes and diagrids, are optimized. Further, optimal stiffness distribution between the core and perimeter structure is studied. The structural efficiencies of braced tubes and diagrids are similar. The performance and efficiency of outrigger structures are very much dependent upon the stiffness distribution between the core, outrigger trusses and perimeter structures.