• Field Notes 18.09.2013

    The Council on Tall Buildings and Urban Habitat recently added a new category for the skyscraper heights they recognize as the world’s tallest: “vanity height.” It seems with the rash of buildings claiming to be the tallest, the Council wanted to distinguish between buildings that have the highest occupied floors and the ones that get their height advantage by adding antennas or other unusable space, hence the term “vanity height.” Has there ever been a more appropriate title?

    The Burj Khalifa, at 828 meters (2,717 feet), is slated to be surpassed as the world’s tallest building next April.  Ground has just been broken on the Sky City Tower in Changsha, China, that will be 10 meters (34 feet) taller than the Burj.

    Did anybody catch the duration of construction for that one? Promise, no typos follow: July 2013 through April 2014. In less than 10 months, they want to construct an 838-meter tall tower. Do you find that hard to believe?

    By comparison, the Empire State Building (EBS), built in the 1930s, was 381-meters (1,250 feet) tall; an antenna added in 1950 extended that by 62 meters (203 feet), for a total height of 443 meters (1,453 feet). The EBS was erected at a rate of 4.5 floors a week. On most towers, erecting a floor a week today is pretty typical. Now do it 4.5 times as fast. Unbelievable! Excavation started in January 1930, actual construction started on March 17, 1930, and the ribbon-cutting happened on May 1, 1931, 15 months later. It’s mind-boggling such a building can be erected that fast.

    And, this before computer drafting, scheduling or even electronic calculators were available to help plan and execute the schedule. The architect only needed two months to draw the plans. They used a previous design as the basis of the EBS, which gave them a little bit of an advantage, but come on, only two months?

    There must have been a lot of preconstruction meetings to talk about planning, sequencing, and execution. While the construction only took 15 months, the planning effort must have been equally as long, right? Take out your daddy’s hand tools, Grandpop’s slide rule, your great grand-daddy’s drafting board and construct such a building today ‘cause that’s how it was done. I’d like to know how much was actually fabricated prior to the start of construction. Just on the structural steel alone, they had to be two-three months or more out in front of the field crews.

    I guess it’s all these “modern conveniences” that allow such a project as the China tower to even pass from conception to an actual project, with everyone chomping on the bit to get going. I wonder how long the original schedule was and how it was decided to shorten it to 10 months.

    As an aside, can you imagine what would have happened (in the case of the EBS) or will happen (in the ChinaTower) if one of the subs falls behind in their work?

    It wouldn’t surprise me to learn that the curtainwall is already fabricated and a floor can be erected in one day that we used to think of being done in a week. Fabricating 60-80 frames a day ramped up to say 150-200 a day, or more.

    With the pressure to be on time, the penalty (and hopefully the reward) clauses for being late (or ahead of schedule) must be enough to overcome the risk. Based on what little is known from my vantage point, is there any way fabrication didn’t at least start a year ago, or more?

    There can’t be anything except prefabricated, site-assembled work, like unitized curtainwall, for all the building systems, including structural, mechanical and electrical; even plumbing modules could help conceivably shorten durations. Ship to the site, set it in place and connect it all together. Can’t wait for welding, can’t wait for concrete to cure. Is there a better/cheaper and, most notably, faster way of construction?

    Or are there so many crews planned to be on site at any one time to handle a site built installation? The necessary equipment to move manpower around the tower must be staggering. I heard that moving crews on the Burj Khalifa could take up to an hour near the end of construction, to move from the ground to getting to an assigned work station, and that, to facilitate that, work starting times were staggered so that everybody wasn’t showing up at the same time. That kind of attention to detail, to moving people and materials around the site, must be so well thought-out and planned for in advance. It can’t be possible to meet such a schedule and not have thought out every little thing, can it?

    Stay tuned, we’re in for a heck of a ride if the developers here ever get this wild of a hair to bring these methods to the States. The paradigm shifts are enough to go looking for the aspirin bottle just thinking about it. Or will everyone be saying, “No problems, just opportunities and challenges?” That would have to be the mindset, right?

    Posted by Blogger @ 9:44 am

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