When you drive past the airport new town area on the S3 highway and look ahead, you will never fail to be attracted by a vast metal “ocean” of blue extending along the silver coastline: The dynamic navy blue color curves like the tides, extends forward and gradually changes into the color bougainvillea purple. The colorful ribbons dances in the wind and tides, and a white dragon knifes through the surging waves and heads up toward the ocean. This eye-catching landmark is nothing but the mega events complex, Shenzhen World Exhibition and Convention Center (Shenzhen World) put in use last month, which boasts the world’s largest metal rooftop.
（Metal rooftop of Shenzhen World）
This feast-to-the-eye rooftop, has since its birth, received letters of recognition from the government thanks to its hard core features. In September, 2018, the super typhoon Mangkhut swept across Shenzhen. The metal rooftop of Shenzhen World at that time was still in the process of installation and wasn’t ready with its anti-wind system. However, despite the most vulnerable geographic location and everything else, it remained intact. This should not only be attributed to the tight control of the architect design, the customized anti-typhoon planning, and the efficient on-site engineering control of the project team, but also their meticulous craftsmanship which drives their constant pursuit of innovation in construction.
Shenzhen World’s metal roof system features altogether 12 functions at a width of 1.18 meters. It’s highly integrated with ant-wind, water-proof, anti-corrosion, noise reduction functions, both good in the look and strong in the functionality.
Blue ribbons dancing in the wind, fine decorations crafts roof elegance
The venue design team has been inspired by the cloud, ribbons, and petals and tried out more than 150 different designs before they finalized the plan with ocean image: the wavy blue ocean and the gradient colored ribbon dancing in the air add radiance to each other and together symbolizes the “Maritime Silk Road”.
However, it is nothing but easy to realize such idealistic design. Creating such dancing wavy images with seven gradient colors over a metal rooftop of 450,000 square meters has made the construction exponentially more difficult. The uppermost decoration layer is made of more than 230,000 pieces of aluminum veneers in 7 different colors. Their specification varies depending on the different locations, which has made each and every one of them unique in the world.
To make the beautiful designs a reality, the project team has numbered each of the 230,000 plus pieces of panels and given them a QR code. Installation of each one has to be meticulous enough to avoid any tiny deviation which may further lead to another round of customization and reinstallation. After arduous efforts, the maritime Silk Road image finally stand out to amaze. This decorating rooftop project really counts as the first in the country given its massive workload and complexity.
（Color design of the rooftop in Shenzhen World）
Looking up close, you will notice that although the panels are all tilted at an angle of 45 degrees, they all appear to be in a straight line looking from aside. The difficulty to achieve such effects is self-evident. Toward the goal, the project team has adopted the accurate positioning control technologies with total stations taking up the three-dimensional coordinates, to tightly control deviation within every ten meters, and guarantee the elegant effects of the magnificent rooftop.
（Aerial photography at Shenzhen World）
The project team has been constantly pursuing perfection, which is demonstrated through their care and precision of a sculptor not only in easy-to-see areas, but also in easily overlooked details. Before visitors’ entry into the lobbies, a majority of them will be attracted to the cornice shaped like a dragon head, but few would notice how the two curved edges are naturally constructed, which is one of the most challenging techniques in the process.
Material wise, the dual-curved design requires both plasticity of flexible materials and the wind and erosion resistance from rigid materials. In the end, the project team has chosen the aluminum veneer and the honeycomb board. They require one mode for one shape, which means each and every piece of panels and boards used has different specifications and sizes. Only customization can perfectly satisfy the needs and create naturally connected effects between each component to offer delicate treat to the eye.
（Cornice of Shenzhen World）
Trump card to withstand once-in-a-hundred-years typhoon
Shenzhen World is situated at the converging area of the Shiziyang and Inner-Lingdingyang, heavily under the influence of the subtropical monsoon season with frequent occurrences of disastrous weather like rainstorms and typhoon. Under such conditions, a super anti-wind metal roof becomes more than important. Then, how can we guarantee this massive roof safe and sound through fierce typhoons?
（Mechanical locking of the roof panels）
After tremendous field trips and comparisons of roof designs home and abroad as well as multiple anti-wind tests, the project team decides to benchmark against the Beijing Daxing International Airport and adopts the same latest roofing materials, i.e. steel panels plated with aluminum and zinc, at the outermost layer of the structure. This material has strong inertia and intensity, highly resistant to corrosion, and really suitable for the city of Shenzhen frequented by rainfalls and typhoons.
In the meanwhile, the project team has adopted an advanced technology from Japan known as the 92/420 standing seam, which enables the roof to be super anti-wind. Unlike the traditional aluminum-magnesium-manganese alloy roof with 65mm of rib of slab, the new locking technology uses steel plank plated with zinc and aluminum with the 92mm rib of slab. Also, with longer side locking shorter side underneath, the connection is much strengthened. Still more, the density of stands and purlins is enhanced so that the wind load will be effectively spread over multiple stands to reduce forces on each.
This advanced set of roof system has successfully withstood the test of a static loading of 15.8 Kpa and a dynamic loading of 15.6 Kpa in laboratories, which will help it survive super typhoons.
Customized retractable double-layer raincoat
Other than frequent occurrence of typhoon, long-time exposure to high temperatures and intense periods of rainfall makes another climatic feature of the southern coastal cities in China. To address this, the project team has customized a retractable double-layer raincoat for Shenzhen World to make its roof watertight.
In order to strengthen the effects, the project team decides to reduce the number of planks to cut down need of splicing. The ultimate result is they resort to the steel panels the same in width compared to the exhibition halls, which has made the steel planks for the roof of Shenzhen World also the longest in the world, at a length of 110 meters for standard halls and 260 meters for the mega hall.
（Steel panels plated with aluminum and zinc on the rooftop of Shenzhen World）
However, also because of the length, such steel panels, which are supposed to be the first line of waterproof system guarding off the venue, now have a shrinkage value at 20 centimeters. Such massive thermal expansion and contraction stress will no doubt cause serious water leakage. Then how should we tackle this thorny problem?
First of all, the project team has chosen the special material of steel planks plated with zinc and aluminum standing seam, which has a low rate of thermal expansion. With wind suction, even if the cross section is distorted in shape, the crucial part remains intact and guarantees auto locking.
Another answer lies in the installation techniques. For effects concern, the project team has innovatively adopted an installation method to use eye bolts to form tens of thousands of anchoring stands, which convert the linear vertical deformation into millions of small deformation along curly lines. Also, the eye bolts can spin easily through retraction to avoid wear and tear and further prevent breakage and leakage.
（Eye bolts illustration）
The 1.5mm TPO waterproofing membrane is the second layer of “soft” armor of Shenzhen World to prevent rainfall leakage. Yet don’t overlook here. It is the pillar support for water prevention. When Mangkhut hit, the steel planks plated with zinc and aluminum were not installed yet. It is exactly this TPO waterproofing membrane that faced the typhoon upfront and withstood the challenge. What’s amazing is that the membrane no only realized zero damage of the metal roof, but also attained zero leakage. Such achievements have well demonstrated the advancing technologies the roofing system adopted for its anti-wind and anti-rainfall functionality, which perfectly interpreted the concept of “Shenzhen quality”.
（TPO water-proofing membrane on rooftop of Shenzhen World）
Sound absorption and noise immunity, hard-core competitiveness witnesses amazing quality
As the protecting wings of the world’s largest venue, the roof system not only stands wind and rain, but also excels in sound absorption.
Located next to the airport and the riverside highway, huge noise disruption almost means a daily routine. So noise reduction has actually made a must-have in this new venue. In acoustics design of the venue, the roof structure is really important. The profiled steel panels and the 100mm thick and 32k sound absorption cotton can effectively reduce noises. They can on the one hand, reduce noise pollution from 80 decibel to less than 50 decibel, and on the other, solve a series of acoustics problems like vibrating echo, acoustic focusing, and long-time reverberation, etc.
In addition, along the wavy roof hides 3 world’s largest sliding skylights and 496 air-operated skylights, which serve as “respiratory airways” on special occasions. For instance, in case of fire, they will be automatically connected with the fire safety system and all open up in 60 seconds to discharge poisonous air and protect people’s safety in the venue.
The rooftop is the most challenging and eye-catching construction area in Shenzhen World. In the extreme timeline, the project team have been working days and nights, trying their best to work on every detail of the venue. Their daring spirit has helped forge the world’s frontier Shenzhen quality, accomplish amazing features of this brand new world class venue, as well as demonstrate people’s craftsmanship in the events industry.