In the contemporary architectural landscape, we find ourselves on the brink of the "megatall" era, a term coined by the Council on Tall Buildings and Urban Habitats (CTBUH) for structures surpassing 1,968 feet. Currently, only three such giants grace our skylines: the Burj Khalifa in Dubai, standing proudly at 2,717 feet since its completion in 2010; the Shanghai Tower, soaring to 2,073 feet in Shanghai, China, finalized in 2015; and the Makkah Royal Clock Tower in Mecca, Saudi Arabia, reaching 1,972 feet, concluded in 2012.
By 2020, this exclusive club is set to double its membership with the completion of Shenzhen's Ping An Finance Centre, Greenland Center in Wuhan, Merdeka PNB118 in Kuala Lumpur, and Jeddah's Kingdom Tower, all currently under construction. To raise these engineering marvels, engineers must pioneer innovative solutions to defy gravity, combat wind vortices, and withstand lateral and seismic loads.
The journey to reach unprecedented heights began with the Home Insurance Building in Chicago, the world's first skyscraper. Erected in the late 19th century, it utilized skeleton construction, employing structural steel to bear the building's weight. The race for height had commenced, and it appears there is no limit to our aspirations. In the coming years, we anticipate witnessing the first building surpassing 3,280 feet (1 km), with proposals reaching even greater heights, including the visionary mile-high skyscraper conceptualized by Frank Lloyd Wright in 1956, known as The Illinois.
The architectural evolution continued with the tube structure, pioneered by Fazlur Khan in the 1960s, incorporating columns along the building's exterior connected to both each other and the core. This design reduced the need for interior columns, optimizing floor space for over 40 stories in subsequent decades. However, one limitation emerged: the base of the building had to grow proportionally to its height, demanding a substantial footprint for supertall structures.
Structural systems continued to evolve. The Burj Khalifa introduced the buttressed core system, featuring a hexagonal central core supported by three triangular buttresses. The Kingdom Tower will mark the next phase with a stayed buttressed core.
Tall structures naturally sway in the wind, and to mitigate this motion, some skyscrapers incorporate mass dampers near their summits. Acting as colossal pendulums, these dampers counteract the building's movement. The Shanghai Tower employs a 1,200-ton mass damper coupled with an eddy current damper, utilizing a copper plate covered in magnets to enhance damping effects.
Engineers also combat wind vortices by tapering building designs, introducing notches or varying cross-sections, and incorporating openings through the structure. However, a critical challenge lies in the building's transportation system. Traditional steel cables limit elevator heights to approximately 1,640 feet due to their weight. To overcome this constraint, engineers have introduced innovations like KONE's UltraRope, featuring a carbon fiber core encased in a high-friction coating, significantly reducing weight and enabling elevators to travel up to 3,281 feet.
ThyssenKrupp challenges the cable issue with the MULTI system, eliminating the need for cables entirely. This magnetic levitation linear motor technology, akin to the Transrapid Shanghai Maglev Train, allows elevators to operate both horizontally and vertically, surpassing the height restrictions imposed by traditional cables.
Moreover, technology plays a pivotal role in design and construction. 3D printing facilitates the prototyping of building components, tested in wind tunnels for efficiency. Building Information Modeling (BIM) and 3D computer modeling enable accurate assessments of real-world performance, minimizing redundant structural elements.
As we witness the ascent of megatall structures, the question of whether this trend will persist remains unanswered. Cost remains a decisive factor, and while currently only four megatall buildings are under construction, over 140 supertall skyscrapers (over 984 feet) are in progress worldwide.
Perhaps a new classification will emerge, introducing terms like "hypertall" or "gigatall." Proposals like the Bride of the Gulf in Basra, Iraq, reaching a staggering 3,780 feet, hint at surpassing even the Kingdom Tower. Ultimately, experts assert that the limit is not in how high a structure can be safely built but rather a matter of the financial investment someone is willing to make to reach unparalleled heights.