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Designing a Super Tall Skyscraper
 

Designing a Super Tall Skyscraper

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    Designing a Super Tall Skyscraper Designing a Super Tall Skyscraper Document Transcript

    • THE SHANGHAI TOWER CASE STUDY Once completed in 2014, the Shanghai Tower, a super tall skyscraper, will be the tallest building in China and the second tallest in the world. Undertaking the design for such a mammoth project is no easy feat. With all the complexities, issues, and possibilities involved, what important lessons can be learned? What are the main highlights of this iconic building? And why did Marshall Strabala, Shanghai Tower’s Chief Architect said, in exclusive interview with IQPC’s Darwin Jayson Mariano, that in designing façade for super tall skyscraper, “movements” matter a great deal? BY: DARWIN JAYSON MARIANO PHOTOS COURTESY OF NICKY ALMSBY and 2DEFINE ARCHITECTURE Like a battle of two Goliaths, emerging economies from Latin America and Southeast Asia are toughing it out in the world stage as both regions try to outdo each other in the arena of Private Equity deals and investments. According to data released by the Latin American Private Equity and Venture Capital Association (LAVCA), private equity (PE) and venture capital (VC) investing in Latin America hits 5-year high in 2012 with firms committing a total of $7.9 billion, representing 21% increase over 2011.
    • Darwin Jayson Mariano: What is your definition of ‘high performance building facade’? Do you notice a pattern or trend when it comes to envelope engineering/design, particularly in China? Marshall Strabala: “High performance building façade” is a label that we attach to a building to say that it’s very sustainable. Basically, this label refers to a unitized system that is factory built to highperformance specifications, be it for high- or low-rise construction projects. Installing a factory-assembled exterior wall system is a lot easier, safer, and advantageous than constructing a system on the building from individual parts. The latter is a basic stick system, and the former is a “unitized system”. In a unitized system, your tolerances are tighter, and more consistent. You can actually get 8mm joints that work better because, when you construct a glass and aluminium wall in situ, weather dominates the process. That is wind, rain and temperature can have big impact on the wall. The contractor has to fight the elements in a stick system, where a unitized system is created in a controlled factory environment at the right humidity and temperature. The High performance coating we use on glass need special handling to produce a well-sealed building. Dust and dirt is another factor that goes away when not building in situ. Right now, China is on an upward curve – it’s approaching the standards of Europe and America, and I imagine they’ll overtake these standards in a few years. So the next step is understanding the patterns that are transferred when it comes to envelope and engineering design. The trend in Asia is moving towards high quality and energy efficiency. Most building performance criteria is controlled by the government, and there is a certain minimum performance that the envelope of all new construction must meet. In addition, the building must be safe for the public, and this is why we are seeing more laminated glass walls to limit the chance of large glass shards falling off buildings. Because of higher performance requirements and sustainability goals of clients, the façade is getting to the point where we have to increase the number of layers in the skin to reduce the amount of energy that transmits through the façade. We are seeing K values of 1.4/1.35, whereas a couple of years ago we were seeing K values of 1.6/1.7. Today, the total envelope of the building has much more stringent insulation requirements than it used to, and this will continue to rise in the future. Please talk about your recent project, the Shanghai Tower. Could you discuss some of the building’s highlights and design strengths? How would you characterize its envelope design? The Shanghai Tower has a very ambitious design. It will be the world’s tallest double skin building. From the beginning, we tried to minimize the amount of façade on the building in order to increase the value of the Project. Basically, what we’re designing is a thermos bottle, a bottle within a bottle that actually increase the insulation value of the building. This is www.facadechina.com
    • like wearing a sweater. You can take the sweater off in the summer, and when it gets colder, you can put it back on to achieve the desired level of comfort. The double skin allows us to use less energy per year than a single skin building. The outer skin or what we call the A wall is not attached to a slab. The A wall is attached to a 350mm dia steel girt, that is from 2 – 12m away from any concrete slab – so there is no adjacent area to install the wall. Yuanda and the General contractor developed a unique set of hanging platforms to install both the Curtain wall Supporting structure, and the exterior wall. Most super tall buildings are only for the use of the tenants, and this means 95% of the building is not public. The public is only allowed on the observation deck through the purchase of a ticket. The Shanghai Tower from the beginning was a building designed for people – both public and private. The completed building takes advantage of the 5 sky lobbies that not only reduce the size of the core because we can stack the elevators, but also create vertical neighbour hoods containing restaurants and other public uses. We call these “Amenity Floors”. This double skin system allows a building to have an enclosed atrium space at each “Amenity Floors” for extra public space beyond the lobby. This “in-between space” allows public access to the edge. Levels 22,37,52,68 and 101 are designed like this. The 83 floor contains a pool and gym, and 118 and above are for the observation population. The double skin is created in eight zones, where each zone has a central cylinder of useable space surrounded by a rounded triangle. These crescents in the atria are from 12m to 7m deep. Therefore, when you www.facadechina.com
    • The Shanghai Tower has a very ambitious design. It will be the world’s tallest double skin building. - Marshall Strabala, Chief Architect, Shanghai Tower get to the edge of your office, you don’t feel like you’re more than 14 stories above the atria, but in reality you are 50 -60 floors above the ground. It’s a very comforting feeling that if the glass broke, you wouldn’t be hanging out in the middle of space 70 floors up. Architecture is the art of making buildings both beautiful and safe. In the Shanghai Tower, there are redundant safety features. The exterior wall on the outside of the building or the “A Wall” is two pieces of Low-E and low iron glass laminated with a product call SGP by DuPont. This is the strongest lamination system we have in the industry, and it creates a very safe environment if a glass panel should break. This lamination keeps the broken pieces of glass from falling and causing injuries. The BME system is designed to both clean and replace the windows. All the system’s materials are chosen for the highest level of performance and sustainability. . The inner wall or the “B wall” was originally thought to be a very simple and easy design; however it became the most technically complex wall I have ever worked on. Conversely, we thought the outer skin would be very complicated, but it turned out to be very easy instead. John Perry was the façade consultant on the project, and his background in structural engineering helped us with the interface of the “Curtain Wall Supporting Structure” – CWSS The inner skin is a very rare system because of the 1 hour fire separation required between the office space and the atria. The core of wall is a formed steel tube clad in aluminium and glazed with a DBF high temperature glass. This glass wall achieves both the fire rating and visual requirements. The lessons we learned was to always go in with open eyes and be prepared for the worst, and just jump for joy when something works out very well. One of the biggest challenges is where the two wall come together and create a structural link to the primary building. There are three points where the CWSS is linked to the base structure actually touching the façade of the building. The inner wall could actually be bolted to the slab, and you could actually work from the slab and have workmen and materials being delivered from the slab area, like in any other building on the planet. However, for the outside skin, there’s no slab, or sometimes the slab is 10 meters away, so it’s a lot harder to install the equipment or the exterior wall panels. You need a platform adjacent to it as you’re installing it, so one had to be developed and installed by Yuanda, the contractor who’s doing the outer skin. Yuanda, the fabricator, installed on a special set of moveable platforms. As the façade is going up, our role becomes that of quality control and we assist in any odd conditions that could come up. We work with all three contractors: Yuanda, Jangho, and Lingyun to refine the design and make sure the detailing is quite tidy and looks good from all angles. In proposing a façade engineering design, do you see a conflict between aesthetics and ROI? Always! All commercial buildings, anywhere in the world, are built for a return on investment. Even museums are built to a budget. Buildings need identity, just like people. Some attract people to the city and others bring people to different parts of the www.facadechina.com
    • city. A large corporate office building or hotel expects a certain level of return, and every operator has a different set of criteria. These design criteria set the cost, acoustics, and performance levels for the project. If done at the beginning the project becomes better. If changed often during design and construction, it will lead to a less than satisfactory result. Every hotel operator requires acoustic separation from room to room, and the façade must meet this criteria. This is done so guests in one room don’t hear the people in the next room through the façade. Putting acoustic separation between hotel rooms is rather easy through drywall and insulation but sometimes, the weak point is in the façade or the interface between wall and façade. So, this struggle between return on investment, performance and aesthetics is always out there, and what you try to do is to achieve the criteria with as minimum amount of material as possible. This minimum amount of material always has a safety factor. The wall should be robust enough so it does not deflect when the average wind blows or creak and break when the building moves. In all exterior walls, movement is required. In super tall buildings, the movements are more extreme and require another level of solutions. Too much movement and the wall leaks, not enough and the wall breaks under pressure. In terms of ROI, the exterior wall of any building is about 20% of the cost, yet the wall is 90% of the look of the building. This piece of equipment is an investment and should be treated as such. You need to maintain it, clean it ( at least twice a year) and repair it, and even replace it, because it really contributes to the image of the building and the image of the building is the first thing people react to. Buildings gain reputation. If something does not work well, people talk and the building becomes a bad place to live or work. This Curbside feeling of quality is very important to leasing. Also, if you let the dirt build up on the façade, it will take longer to clean and hurt the image of the project. So is it easy to clean? Is it easy to replace? Does it look good between cleanings? These are the question we always ask. Here’s a key thing: if you can design your façade so the dirt and the rain don’t actually show up between cleanings, you’re ahead of the game. The gaps between the façade pieces actually channel the rain and the particles in the air, so it doesn’t look like it’s dirty between cleanings. That’s what we strive to do. We try to plan where the water goes so we’re not getting stains and dirt doesn’t build up where we don’t want them; we always specify weeps in our building to get internal moisture out of the building. We actually look for a high return on investment not 5 or 6 years, but 50 years, and I think that looking longer-term is the right way to do it. Do you think building owners are receptive to these ideas? Yes, all building owners want a good ROI and these criteria help improve the profit. Sometimes with very complex and unusual shapes the fabricators can help you achieve the right aesthetics with the lowest cost. The owner sets the price, the architect sets the look, the façade team sets the performance and the fabricators pull them all together. And sometimes, the fabricator comes up and says, if we change this and adjust that, we can reduce the cost of façade and make it look like 90% of what the architect had in mind. You should always be a little flexible and listen. Allowing the fabricator input early on is always good for the ROI. www.facadechina.com
    • Once completed, the Shanghai Tower will be the tallest building in China. What important lessons one must learn in designing façade for super tall skyscraper? The lessons learnt are Movement, Movement and more Movement. First of all, the overall movement of the building. This can be as much as two meters at the top! The distance the building moves must be accounted for in the façade. From a comfort standpoint, you need to control the acceleration, not the distance. It’s important to fine-tune the structural system to allow enough movement so earthquakes and wind forces are balanced and correctly mitigated. This overall movement is very high at the top and very low at the bottom. Panels at the top can be significantly damaged, while the panels at the bottom of the building might not have much impact at all. In super tall buildings, the details might change as you go up. But there is fourth movement that you need to be aware of, especially in this idea of a double-skin building: the movement induced by high temperatures, or fire. We don’t want fire to cause breakage and movements in the structure that might cause something else to break. In the rare event of a fire, you need to make sure that smoke does not migrate from one part of the building to another. We also need to think of what a fire does to the façade, which can result in pieces falling off. Thirdly, after the fire is out, did the temperature impact the system that might make it unsafe for the fireman who is putting out the fire? We have to make sure that there are no “second-order repercussions” from a fire. This gets very complicated and we often employ RJA as a fire consultant to review the work. At the end of the day, it really comes to down to Movement, Movement, Movement, Movement, and even more Movement. The second movement pertains to all the nonreversible changes in the size of members (i.e., column shortening). Under loading things change. In super tall buildings, this can be very significant. Then there is settlement of the entire structure that might affect the façade. There is movement vis-àvis deflection. Deflection is the reversible beam movement under load. So we have to account for that when designing the façade system. If we had 12 meter long beams, the exterior wall panels need to accommodate this centre beam deflect so as not to lockup under the overall building movements. Panels in the middle of the span need enough adjustments to make the appearance level on the outside of the building. Then we get to the third, a non-reversible movement in tall buildings, called concrete creep. As you start stacking these floors on top of each other and going up to, say, 120 floors, the columns start to get a little shorter on the ground level. So you have to plan for that column shortening either in the façade or in the concrete itself. Generally, we start adding taller “stack” joints in the façade at the bottom than at the top. www.facadechina.com
    • Marshall Strabala AIA AFAAR LEED ap. is the co -Founder and Design Partner of 2DEFINE Architecture. He is an American architect, living in Shanghai, who has lead the design team of three of the ten tallest “constructed” buildings in the world. For the last three years, Strabala has been the principal of his own architectural firm, with over 30 years of combined experience. He was an Associate Partner at SOM in Chicago, and the only Director of Design M. Arthur Gensler Jr. & Associates, Inc. Currently, Strabala and 2DEFINE Architecture are the chief architect for the Shanghai tower scheduled for completion in 2014. Hear more from Marshall Strabala and other distinguished speakers at the 3rd Annual Facades Design and Engineering China 2013, happening on 18-21 June at Shanghai, China. www.facadechina.com About the Author: Darwin Jayson Mariano is the Online Content Manager and Regional Editor - Asia for International Quality & Productivity Center (IQPC), a leading producer of events and conferences for business leaders around the world. Connect via LinkedIn or email darwin.mariano@iqpc.com.sg Disclaimer: Please note that we do all we can to ensure accuracy and timeliness of the information presented herein but errors may still understandably occur in some cases. If you believe that a serious inaccuracy has been made, please email darwin.mariano@iqpc.com.sg. This article is provided for information purposes only. IQPC accepts no responsibility whatsoever for any direct or indirect losses arising from the use of this report or its contents.