Photo credit: Gensler
The curtain wall is being installed on the Shanghai Tower, and so far I am very impressed with the way that fabrication and installation are progressing. The hard work of our project team, in particular Michael Peng and Ben Tranel, is the reason we have been able to streamline this complicated process. Ben and Michael have worked with Yuanda, the curtain wall contractor, to simplify the design and to ensure the integrity of construction.
From day one we knew that the curtain wall would be one of the building’s most challenging aspects from a design, engineering, and constructability perspective. It is difficult enough to design a double-skin building, but one that requires the outer skin to be constructed at continuously varying distances from the inner curtain wall has never been done before.
Allow me to get technical for a moment. The outer curtain wall is designated as “A,” while the inner curtain wall is “B.” The “B” wall is constructed against the concrete floor slabs, whereas “A” is constructed at points whose distance from “B” range from two feet to 33 feet.
Photo credit: Gensler
As many of you know, the “A” curtain wall employs a system of suspended rods and girts and is hung from an outrigger truss structure above, and the tolerances of the underlying structural system are critical to an accurate installation of the façade. We are essentially hanging 14 floors of curtain wall on a series of ring beams braced back to the core. The design is much like a bicycle wheel, with spokes radiating from the core outward. And if that isn’t complicated enough, the wall is essentially being installed out in space, meaning that there is no structural slab, so the beams must tie into prefabricated tabs on the structural ring. We are constructing the outer curtain wall on series of suspended work platforms hanging in the atrium space. Establishing the work points for installation tolerances to the nearest millimeter within the context of a complex structural system that defies Cartesian coordinate geometry has, needless to say, been one of the project’s primary challenges.
Photo credit: Gensler
What has surprised us the most in terms of construction is the tight tolerances of the curtain wall and the structural bicycle ring. As we load the cable structure with the weight of the curtain wall, the structure deflects, which has to be anticipated in the initial setting out of the curtain wall unit. Since all of the deflection over 14 floors accumulates, anticipating the correct amount of deflection is a major challenge. With the first floors complete, the façade is fitting to the structural steel nicely, and the structural girt on the ground along with the vertical bushing is providing lateral movement control and structural stability.
A concern I’ve had from the beginning of the project is the impact on light and views that the double curtain wall will have on the building’s tenants and occupants. There was always the potential that the curtain wall framing, glazing, and structural system would obstruct views, and it has been difficult to envision what one would see looking across the atrium space to the outside world.
Photo credit: Gensler
At this point I am very pleased (and somewhat relieved) that the views and light look great. The glazing is very transparent, and there is a nice sense of natural light filtering through the outer curtain wall and across the atrium space. There is a minimal obstruction to views as you look directly out, and slightly more as you look up or down.
Photo credit: Gensler
What I didn’t anticipate is that as one walks the floor of office spaces, the outer curtain wall undulates, moving closer and then farther away from you, creating three distinct atriums for each section of the building. This “movement” offers a dynamic aspect to the occupant experience. It’s very cool!
We are up about 12 floors, and life is good. Until next time …
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Dan Winey is a member of Gensler’s Board of Directors and the Regional Managing Principal of our Northwest region. Our offices in Shanghai and Beijing were launched under Dan’s purview, and he’s been a key member of our Shanghai Tower team from initial project win through construction. Contact him at dan_winey@gensler.com. |