• International Journal of High-Rise Buildings
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• v.10 no.3
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• pp.179-191
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• 2021

Tall buildings have generally been developed as solo towers. With the increase of the heights of tall buildings from about 10-story buildings to supertall and megatall buildings, their structural systems have evolved from interior structures to exterior structures and combined/mixed systems. This paper reviews structural systems developed for solo supertall and megatall buildings and discusses the challenges they face in terms of structural performance and architectural design as the building heights are ever increased. As a viable and more sustainable design alternative to extremely tall solo towers, superframed conjoined towers are presented. Their structural performances are investigated in comparison with solo tower structures. Further, architectural potentials of superframed conjoined towers are explored through design studies.

• International Journal of High-Rise Buildings
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• v.9 no.4
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• pp.387-396
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• 2020

While tall buildings are an essential building type to accommodate an ever-growing urban population, as buildings become taller and taller, many design challenges arise. As floor spaces are repeated vertically, the occupants' natural horizontal circulation-based social interactions are limited. As buildings become ever taller, safe evacuation to the ground level becomes more challenging in emergencies. With respect to safety as well as serviceability, one of the most fundamental design challenges of exceedingly tall buildings is their structural systems that make the physical existence of tall buildings possible. While many different design solutions can be sought to resolve these issues as well as other design challenges of extremely tall buildings, this paper investigates the potential of conjoined towers to create more livable and sustainable vertical environments. Emphasis is placed on the social and structural capabilities of conjoined towers in providing enhanced social interactions and more efficient ultra-tall structures. The related brief history of conjoined towers is presented. To understand their current status, contemporary design practices of conjoined towers are discussed. Lastly, a new concept of superframed conjoined towers developed for exceedingly tall building complexes is introduced through design studies. Though envisioning future tall buildings is challenging, conjoined towers can be among the strong candidates toward more livable and sustainable vertical urbanism.

• International Journal of High-Rise Buildings
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• v.7 no.3
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• pp.197-214
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• 2018

Tall buildings which began from about 40 m tall office towers in the late $19^{th}$ century have evolved into mixed-use megatall towers over 800 m. It is expected that even mile-high towers will soon no longer be a dream. Structural systems have always been one of the most fundamental technologies for the dramatic developments of tall buildings. This paper presents structural systems employed for the world's tallest buildings of different periods since the emergence of supertall buildings in the early 1930s. Further, structural systems used for today's extremely tall buildings over 500 m, such as core-outrigger, braced mega-tube, mixed, and buttressed core systems, are reviewed and their performances are studied. Finally, this paper investigates the potential of superframed conjoined towers as a viable structural and architectural solution for mile-high and even taller towers in the future.

• International Journal of High-Rise Buildings
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• v.8 no.1
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• pp.29-36
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• 2019

Tall buildings are one of the most viable solutions to deal with the global phenomenon of rapid population increase and urbanization. While tall buildings are an essential building type to accommodate ever-growing urban population, as buildings become very tall they also produce many critical design challenges related to social interactions, emergency egress, structural systems, etc. While many different design solutions can be sought to resolve these challenging issues of tall buildings, this paper investigates potential of conjoined towers in producing more livable and sustainable megatall building complexes with an emphasis on their capability in efficiently providing exceedingly tall building structures.

• International Journal of High-Rise Buildings
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• v.12 no.4
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• pp.307-320
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• 2023

Tall buildings are built with an abundant amount of materials, including structural materials, coming from our limited natural resources. Tall buildings that began from about 10-story tall office towers have evolved to over 150-story tall mixed-use megastructures. As a building becomes taller, structural material requirement to resist lateral wind loads becomes exponentially larger. Therefore, it is crucial to employ efficient structural systems and optimize their design, which will contribute to sustainable vertical built environments through preservation of resources. Tube type structures with large perimeter diagonals are among the most efficient structural systems for tall buildings. Developments of braced tube, braced megatube, diagrid structures, and their optimal design strategies are reviewed. Superframed conjoined towers, produced by interconnecting multiple clustered braced tubes, are presented as a new design direction to achieve not only structural but also architectural and social sustainable design goals.