Wednesday, November 11, 2015

Quite a bit more than the whole 9 yards...

In the annals of construction porn, this is an oddly mesmerizing little gem: an 8.5 minute condensed time-lapse video of the 16 hour foundation pour of the new super-skyscraper that's now underway in the heart of San Francisco.

Wired reports with more details: It Took 18 Hours to Pour San Francisco's Biggest-Ever Concrete Foundation

All that concrete did not slop down into an earthy void. In the weeks leading up to the pour, workers constructed a subterranean lattice of rebar—12 layers high, with six inches separating each layer. "We used 5 million pounds of number 18 rebar, the largest size available," says Tymoff. At two and a quarter inches in diameter, grabbing a bar of No. 18 is like gripping the fat end of a baseball bat. It took eight iron workers to lift each 45-foot segment into place. That cagework will act as the foundation’s skeleton, but during the pour it also served as a catwalk for workers holding the cement hoses or the massive vibrators used to ensure the concrete had no air pockets.

The hardened slab, in all its mightiness, is but half of the tower’s earthquake protection. It will keep the building from toppling sideways, but what about sliding back and forth? In a big earthquake, the ground is actually trying to slip sideways underneath the building. "You need something to keep you from changing addresses," says Joseph. Those somethings are called piles, in essence underground stilts connecting the building with the bedrock. In the lowlands of San Francisco’s Financial District, bedrock is 300 below street level. "We have 42 piles that go all the way down and are socketed 15 to 25 foot deep into the rock," says Tymoff.

And of course, for even MORE detail, don't miss the wonderful site run by architects Pelli Clarke Pelli: Salesforce Tower.

At its base, Salesforce Tower connects directly to the transit center, which will house 11 Bay Area transit systems. On top of the Transit Center and linked directly to the tower is a 5.4-acre public park, which will offer recreational, educational, and nature activities. The park has two roles: the future anchor of the neighborhood and a key element of the project’s sustainable design strategy.

Each floor of the tower will have integrated metal sunshades, calibrated to maximize light and views while reducing solar gain. High performance, low-​emissivity glass will also help to reduce the building’s cooling load. Cooling may be provided in part by heat-​exchanging coils wrapped around the tower’s foundations. The tower and transit center also include comprehensive water recycling systems. In addition, high efficiency air-​handlers will take in fresh air on every floor.

Or, if you just can't stand it, head on over to the skyscraper's own website run by Boston Properties, and keep up with the minute-by-minute progress on Construction Cam!

It's interesting how these giant construction projects go. A few years back, I was completely fascinated by the new Bay Bridge, and in particular by the custom barge-based floating crane that was commissioned and delivered especially for the project: the Left Coast Lifter.

Now the bridge is built (and in fact the old bridge is pretty well completely torn down and removed), and the Left Coast Lifter hasn't been around these parts for years.

But last week, when I was in New York, we happened to make a side trip (to Storm King -- that reminds me, I need to blog about that, too!), and we found ourselves crossing the Tappan Zee Bridge.

And there, what did I see to my delighted eyes?

It's the Left Coast Lifter!

Alive and well, it's happily sitting in the Hudson River in upstate New York, contentedly building the new bridge.

The folks on that side of the country call it the I Lift NY supercrane.

But as we whizzed by on the super-speedway I could still make out the words painted across the bow:

Left Coast Lifter

So there you go.

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