Many urban planners predict that by 2050, more than 6 billion people will live in cities, and in places where building outwards isn't an option, the only way to keep up with the growing density is to build up. Building taller always comes with numerous challenges and also a not-so-subtle competition for architecture firms to have their name tied to the biggest buildings. Almost as fast as a building is named one of the tallest in the world, another one makes its way to the drawing board, a few years later taking the title. While the sky’s the limit, how does this impact the constructability of projects, and what feats of construction methods and materials have enabled us to build into the clouds?
First, it’s important to understand how to technically define tall buildings. The Council on Tall Buildings and Urban Habitat (CTBUH) defines two sub-groups of buildings that achieve significant heights. A “supertall” building is defined as being 300 meters (984 feet) or taller, and a “megatall” structure reaches at least 600 meters (1,968 feet) high. At today’s pace, at least one supertall skyscraper is completed annually, with 132 supertall skyscrapers having completed construction as of June 2020. The Burj Khalifa is still the world’s tallest skyscraper, measuring 2,722 feet, or just over half a mile. Recently, after 8 years of construction, the Merdeka 118 in Malaysia completed construction and measured only 500 feet shorter than the Burj Khalifa. It’s predicted that the world’s first mile-high building could be completed within the next 30 years, also bringing in a new trend of buildings that stand over 3,200 feet tall.
Tall buildings come with all sorts of mechanical and structural issues. How long will people wait for an elevator when they’re traveling from the lobby to the 200th floor? How will megatall buildings withstand natural forces that we can predict and ones that we can't? Many of these issues are solved by hacking the modern materials and systems that we are already familiar with and creating ones that support an innovative construction industry.
One of the main issues when building tall structures is the ability to keep construction materials close to the site, as the building’s footprint and the surrounding area are typically small, especially in urban areas. This creates issues for constructing framing members, as precast panels are often brought to the site as they are ended due to their inability to be stored. However, many contractors are now using a tilt wall construction process, allowing them to pour and assemble the panels on site and using a crane to lift them into place.
Skyscrapers are also looking towards steel alternates, but as a building increase in height, its weight becomes a significant issue. Aluminum offers a lightweight alternate with its easy extrusion process that enables it to conform to a variety of shapes for almost any façade design. It also reacts well to stress from internal structural elements and exterior forces such as rapidly changing temperatures and seismic disruptions from earthquakes. Carbon fiber is another emerging material, also light in weight, but it features long strands that are interwoven together to form a fabric-like structure. As a result, it is significantly stronger than steel, enabling it to be implemented into buildings that receive high-impact loads. Carbon fibers are already making their way into precast concrete elements. By placing the mesh into the concrete mixture instead of traditional steel mesh, the overall weight of the structural unit decreases, allowing it to be lifted into place safely, and secured knowing that it maintains significant structural integrity.
Even more future-forward are ideas of what the future of concrete might look like. Concrete has remained largely unchanged for hundreds of years. While it is extremely durable, many people are pushing for new alternatives as it continues to be a major source of CO2 emissions. Some researchers are looking into bio-concretes, that have the ability to heal their own cracks by adding in limestone bacteria that can prolong the life of concrete for up to two hundred years. Even wood, which seems unlikely to ever be used as a major structural element in a megatall structure, is finding a new life in cross-laminated timber structures that give it comparable strength to steel. To demonstrate timber’s abilities, Sumitomo Forestry, a Japan-based design firm, recently revealed its plans to build a 350-meter tall wooden structure in Tokyo. Taller buildings are just on the horizon, and the construction materials and methods are quickly catching up to be able to make these mile-high dreams a reality.
This article is part of the ArchDaily Topics: The Future of Construction Materials. Every month we explore a topic in-depth through articles, interviews, news, and projects. Learn more about our ArchDaily topics. As always, at ArchDaily we welcome the contributions of our readers; if you want to submit an article or project, contact us.
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