Geometrical patterns for diagrid buildings: Exploring alternative design strategies from the structural point of view

Seismic analysis of high-rise mega-braced frame-core buildings

SUMMARY

The procedures and formulations suggested in literature for the design of diagrid structures start from the assumption that diagonal sizing process is governed by the stiffness requirements, as usually occurs for other, less efficient, structural types, and that member strength demand is automatically satisfied by the cross section resulting from the stiffness requirements. However, thanks to the high rigidity of the diagonalized facade, strength requirements can be of paramount importance and even be the governing design criterion. In this paper, stiffness and strength design criteria for diagrid structures are examined and translated in simplified formulae for quick member sizing. The application of the two approaches for the design of a 100-storey building model, carried out for different diagrid geometrical patterns, gives the opportunity of discussing the relative influence of stiffness and strength on the design outcomes, in terms of resulting diagonal cross sections and steel weight, as well as on the structural performance. Copyright © 2013 John Wiley & Sons, Ltd.

Design criteria for diagrid tall buildings: Stiffness versus strength

Summary
In recent years, diagrid structures have received increasing attention among both designers and researchers of tall buildings for creating one-of-a-kind signature structures. This paper presents a state-of-the-art review of diagrid structures. First, various diagrid configurations, main factors affecting their behaviors, and related design parameters and approaches are discussed. Then, diagrid applications for free-form steel and concrete structures are introduced showing the diagrid applicability for complex structures followed by recent advances in structural design of diagrid connections, diagrid nonlinear behavior, and structural control of diagrids. Recent studies about a new variation of tubular and diagrid systems, hexagrids, are discussed briefly. Finally, the diagrid potential in design of sustainable buildings is delineated.

Diagrid: An innovative, sustainable, and efficient structural system

Summary
Unlike vertical columns of traditional structure, diagrid structural systems for tall buildings have special inclined columns. Due to the inclined columns, a diagrid structural system for tall buildings produces axial force along the column direction under horizontal load, which has the advantage of resisting horizontal wind load and seismic load and gives more freedom to architectural design, so a diagrid structural system for tall buildings becomes an effective new structure style for tall and super-tall buildings. Theories and tests regarding the diagrid structural system for tall buildings have been intensely researched since the exterior tube of diagrid structural system for tall buildings was first proposed by Torroja in his seminal book. At present, studies for mechanical characteristics, joint form, theories, and tests have been systematized. This paper systematically summarizes existing research achievements of the diagrid structural system for tall buildings and confirms that the structure has larger lateral stiffness and good seismic performance. Based on the favourable performance of concrete-filled steel tubes, this paper advises the use of concrete-filled steel tube columns as the columns in diagrid structural systems for tall buildings.

A review of the diagrid structural system for tall buildings

SUMMARY
The originality of form is one of the new trends that can be identified in the current design of tall buildings. In this design trend, the so-called diagrid structures, which represent the latest mutation of tubular structures, play a major role due to their inherent esthetic quality, structural efficiency and geometrical versatility. In this paper, an overview on application of such typology to high-rise buildings is carried out; in particular, in the first part of the paper, the peculiarities of diagrid systems are described: starting from the analysis of the internal forces arising in the single diagrid module due to vertical and horizontal loads, the resisting mechanism of diagrid buildings under gravity and wind loads is described, and recent researches and studies dealing with the effect of geometry on the structural behavior are discussed. In the second part of the paper, a comparative analysis of the structural performance of some recent diagrid tall buildings, characterized by different number of stories and different geometries, namely the Swiss Re building in London, the Hearst Headquarters in New York and the West Tower in Guangzhou, is carried out, and some general design remarks are derived. Copyright © 2012 John Wiley & Sons, Ltd.

Maurizio Toreno

Papers

Diagrid structures for tall buildings: case studies and design considerations