With nearly 25 million people, Shanghai is the largest metropolis on Earth. It’s home to the largest daily commute of people in the world. It’s a global financial center in the world’s fastest growing region, and serves as the world’s busiest container port. But it also accounts for over 1 billion gallons of sewage daily, and smog levels that on certain days make going outside dangerous. This is the scene of an emerging China – and it’s continuing to grow at an unprecedented rate, prompting leaders and residents to confront growing pains with new solutions.
Google a skyline picture of Shanghai from just a few years back compared to today; it’s awe-inspiring. Over the past decade alone, the population has increased by 37 percent, with five times as many vehicles added to the streets during that time, with no signs of slowing down. More people and vehicles mean more congestion. In a city where space is fast-becoming the most precious commodity, Shanghai is literally running out of it. The obvious need is to build ‘up,’ but the challenge is to do so in a smarter way.
Skyscrapers have traditionally been an American phenomenon, but a new landscape has been unfolding over the past few decades – a sort of perfect storm between construction needs and material innovation – and the desperate need for space in many cities has only added fuel to the fire for vertical investments.
As Judith Dupré, author of “Skyscrapers: A History Of The World’s Most Extraordinary Buildings” notes, we are “in the midst of a new skyscraper boom. What started in the U.S. has since followed to Asia. When densely populated cities attract even more people, there’s literally nowhere to go but up.” She adds that, “materials such as high-strength concrete and reinforced polymers have enabled buildings to go up with increased safety at a lower cost.” China alone currently has more than 14 buildings and another 8 under construction that are taller than the Empire State Building. These are literally cities within cities.
Visionaries in Shanghai are embracing the idea that ‘new problems require new solutions,’ and, in 2008, began construction on the Shanghai Tower. After topping out in August, 2013 at 2,073 feet, the Shanghai Tower is now officially the tallest building in China, and the 2nd tallest building in the world. Standing out among the packed skyline of this city is a tall order, but that’s exactly what the Shanghai Tower sets out do in more ways than one.
The project’s developer is the Shanghai Tower Construction & Development Co., Ltd; Gensler is the Design Architect; the Architectural Design and Research Institute of Tongji University is the Architect of Record; Thornton Tomasetti is the structural engineer; Cosentini Associates are the mechanical, electrical and plumbing engineers; RWDI is the wind consultant; and Dow Corning is the material supplier for sealants.
The development is slated for completion next year in 2015.
“Shanghai Tower represents a new way of defining and creating cities,” said Art Gensler, FAIA, Founder of Gensler. “By incorporating best practices in sustainability and high-performance design, by weaving the building into the urban fabric of Shanghai and drawing community life into the building, Shanghai Tower redefines the role of tall buildings in contemporary cities and raises the bar for the next generation of super-highrises.”
Shanghai Tower is located in the Lujiazui Finance and Trade Zone, an area of Shanghai that was farmland a little over 20 years ago. The area is China’s first super-tall district, as Shanghai Tower rises to complete a trio of towers including the adjacent Jin Mao Tower (1,380’) and Shanghai World Financial Center (1,614’). “With the topping out of Shanghai Tower, the Lujiazui trio will serve as a stunning representation of our past, our present and China’s boundless future,” said Jun Xia, Shanghai Tower design leader and Gensler principal.
The tower takes the form of nine cylindrical buildings stacked atop each other with a central 90-foot by 90-foot concrete core, literally and figuratively the heart of the building, which acts in concert with a system of outriggers and supercolumns.
Two-story belt trusses support the base of each zone, marking the divisions of the building into nine zones. The inner layer of the double-skin façade encloses the stacked buildings, while the exterior façade creates the building envelope. The spaces between the two façade layers create nine atrium sky gardens.
Each zone can be considered an independent city or village. People can go up directly to the respective zone from the ground and then take shuttle elevators to each floor. This can reduce the pressure of high population concentrations on the ground level. Every single zone has its own mechanical floor and refuge floor, which establishes an independent system within the zone that can save energy and enhance the evacuation process of the whole building.
Each of the building’s ‘neighborhoods’ rises from a sky lobby at its base – a light-filled garden atrium with the intent of fostering socialization. Much like plazas and civic squares in traditional cities, the public sky atria offer spaces within Shanghai Tower for interaction and community gathering space with restaurants, cafés, coffee shops and convenience stores, as well as lush landscaping throughout.Shanghai Tower’s interior and exterior skins are transparent, establishing a visual connection between the tower’s interiors and the urban fabric of Shanghai. On the ground level, retail and event spaces, in tandem with abundant entrances on the site and a subway station under the building, continue the physical and visual connections between the tower and the city.
The structure sits atop a foundation that includes the use of nearly 1,000 concrete-and-steel bore piles, 3 feet in diameter, driven into the ground, and an 18-foot deep Mat Foundation that required a team of trucks to continuously pump and pour concrete over a 63-hour period in 2010.
The Shanghai Tower, LEED Certified, boasts figures of 121 floors, over 300 hotel rooms in what will be the world’s tallest hotel, 1800 parking spaces, and includes the world’s fastest elevators. Mitsubishi Electric, the supplier of all 106 elevators, including three express elevators with never before-seen speeds up to 40 mph (nearly 60 feet per second.)
WIND-TUNNEL TESTING AND ROTATIONAL DESIGN MINIMIZES SWAY
While most skyscrapers account for wind sway in the design, the Shanghai Tower’s directive was clear – sway was to be minimized to the fullest extent. To complicate matters more, Shanghai sits directly on the coast and is a common target for annual typhoon seasons that bring extreme gusts of wind.
Gensler and structural engineer, Thornton Tomasetti, refined the tower’s plans to feature a tapered profile with a curved façade, and a geometric rotation, or ‘twist,’ of 120 degrees, in an attempt to reduce wind loads. To accurately measure the cable-and-ring support system, the team positioned lasers on nearby buildings. Using software loaded with these dimensions, fabricators produced curtain-wall panels that were assembled and verified in the factory, which allowed for precise tolerances.
Architects and engineers also implemented wind tunnel testing experiments of the largest proportions, using 1:85 scale models of the proposed tower and surrounding buildings, including internal temperature and air-flow distribution simulation to validate their design. Rounding the corners, where wind force is greatest, plus shifting those corners as the building climbs has a significant effect to reduce pressure from wind. The wind tunnel testing proved the asymmetrical design successful, reducing the building wind loads by 24 percent. Furthermore, the result supported a lighter structure that saved $58 million in materials.
In addition to the curved façade design, the top of the building features a Tuned-Mass Damper (TMD) to counter-act ‘sway’ and improve occupant comfort. At 12 metric tons, it essentially acts as a counter-balance, and is computerized to detect the wind force pushing the building one way, and actually pushes it back in the other direction.
Sustainability is at the core of Shanghai Tower’s design. The building features two skins of glass, or curtain walls. It’s like a building inside of a building. With over 1.4 million square feet of the most technologically advanced glass used anywhere in the world, the building’s transparent inner and outer skins admit maximum natural daylight, thereby reducing the need for electric light. The tower’s outer skin also insulates the building, reducing energy use for heating and cooling. The circular inner-glass façade requires 14 percent less glass than a square building of the same total floor area, and the outer-glass features an ‘intelligent skin’ that is solar-oriented with a ceramic fritted dot-pattern of varying density and shapes to help filter and control the amount of direct sunlight. The overall energy conservation rate of the Shanghai Tower is 54.3%, which is 21% better than similar buildings.
Over 270 Wind turbines located directly beneath the parapet generate on-site power for the upper floors of the building and power the building’s exterior lighting needs, generating 300,000 kilowatt-hours per year of green electricity. Overall, Shanghai Tower incorporates 43 sustainable strategies that will reduce energy consumption by 21 percent, and the building’s carbon footprint by 34,000 metric tons per year.
As the purpose and design of super-tall structures continues to evolve, the Shanghai Tower embodies the ideal solution for a high-density urban center such as Shanghai, and the city itself is the perfect petri dish for such an experiment in the face of unrelenting growth.
Feature Article by E. H. Evans from April 2014 Wire Rope Exchange