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View Poll Results: Which transbay tower design scheme do you like best?
#1 Richard Rogers 39 7.88%
#2 Cesar Pelli 98 19.80%
#3 SOM 358 72.32%
Voters: 495. You may not vote on this poll

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  #3281  
Old Posted Sep 16, 2018, 8:52 PM
mt_climber13 mt_climber13 is offline
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We have reached peak Salesforce logo
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  #3282  
Old Posted Sep 16, 2018, 9:38 PM
pseudolus pseudolus is offline
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Originally Posted by mt_climber13 View Post
We have reached peak Salesforce logo
unless, as reported, they lease 45 Fremont too
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  #3283  
Old Posted Sep 26, 2018, 12:26 AM
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Quote:
Transbay Transit Center closed after crack found in steel beam
Photo of Matier & Ross
Matier & Ross Sep. 25, 2018 Updated: Sep. 25, 2018 4:44 p.m.

After a major crack was discovered in a steel beam that supports the roof garden of the new, $2.2 billion Transbay Transit Center, officials decided Tuesday afternoon to close the terminal and move all bus operations to the nearby temporary terminal.

The temporary terminal at Howard and Main streets, was used for eight years while the new building was being constructed. It will be used until officials have had a chance to thoroughly inspect the fissure.

“I’m told there’s a problem with a steel beam,” said Mohammed Nuru, chairman of the Transbay Joint Power Authority, which oversees the 2½-block-long transit center and roof-top park.

Inspectors were on the bus deck early Tuesday checking out one of the steel beams that supports the roof garden. The beam is concealed by ceiling panels and topped by 5 or 6 feet of soil.
https://www.sfchronicle.com/bayarea/...t-13257805.php

Buses rerouted to temporary terminal--glad it hasn't been demolished yet. Maybe they used second hand parts (like Bart) or substandard steel (like the Bay Bridge) here too.
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  #3284  
Old Posted Sep 26, 2018, 12:37 AM
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This is infuriating! It's also near the Millennium Tower...

Now, both Fremont and First Streets have been closed. Even without Dreamforce in town, traffic pandemonium is reigning.

https://www.bizjournals.com/sanfranc...905&j=84035741

Last edited by viewguysf; Sep 26, 2018 at 12:49 AM.
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  #3285  
Old Posted Sep 26, 2018, 3:01 AM
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Fremont St tonight

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  #3286  
Old Posted Sep 26, 2018, 4:52 PM
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So projects here are being built at 1/10th the speed of projects in China, but at the same (or possibly less) quality?
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  #3287  
Old Posted Sep 26, 2018, 4:57 PM
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People just need to calm down. It's probably a one off minor defect that's easily remedied that's not indicative of some sort of massive structural miscalculation.
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  #3288  
Old Posted Sep 26, 2018, 7:16 PM
mt_climber13 mt_climber13 is offline
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Worst Infrastructure Week ever.
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  #3289  
Old Posted Sep 26, 2018, 7:27 PM
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Quote:
Originally Posted by Busy Bee View Post
People just need to calm down. It's probably a one off minor defect that's easily remedied that's not indicative of some sort of massive structural miscalculation.
That's not what engineers are saying . . . necessarily:

Quote:
Q: Is such a discovery typical, like the usually innocuous cracks that emerge in a stucco wall?

A: No. “A structural steel beam should never crack,” said Joe Maffei of Maffei Structural Engineering in San Francisco. “It should not crack.”

[color=blue]Q: This is obviously bad news. How bad might it be?[/color

A: “Any kind of a crack in a structural steel beam has potential implications,” Maffei said. “You need to always be careful about cracks because they can grow. And their failure can be sudden.”

Q: What might be the cause?

A: Two possible culprits are a fabrication problem — something went wrong when the beam was manufactured — or the beam is supporting more weight than it’s designed to bear.

If it’s a manufacturing problem, there could be hidden stress in the beam. These giant slabs of metal often consist of plates of steel welded together, and one area inspectors are sure to examine is any hint of imperfections in the steel.

If the weight above the beam is the problem — remember, there’s a 5.4-acre park on the roof — one indication could be the configuration of the crack.

“If there’s a horizontal crack running the length of the beam, there could be too much weight on the beam,” said David Friedman, a senior principal at Forell/Elsesser Engineers.

Q: Could the crack mean that the transit center is sinking and tilting, like the Millennium Tower next door? Or could the two problems somehow be linked?

A: Not likely. The transit center’s foundation is a 5-foot-deep, 60,000-ton concrete mat. Work on the foundation was completed in 2014, and there has been no evidence since then of ominous settling.

Q: How will they fix the problem?

A: It depends, of course, on the source of the problem. But, according to Friedman, “it’s easier to strengthen a steel beam than a concrete one.”

If the crack is an isolated problem, the beam can be reinforced by welding additional steel panels to its underside.

Q: What will the inspections involve?

A: There are any number of tests, such as taking samples of steel from the beam — without weakening it, of course — and seeing how much strain they can withstand. But there are also straightforward measurements of the crack’s length and depth to be done.

“If it’s a horizontal crack running the length of the beam, then the problem could be the load,” Friedman said.

And if that’s the case? “I’d start looking at similar beams in similar (stress) conditions” — which can take a lot of testing and time.
https://m.sfgate.com/bayarea/article...p?t=b3a3a3bed5

And if it isn't an isolated problem?
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  #3290  
Old Posted Sep 26, 2018, 7:30 PM
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Originally Posted by homebucket View Post
So projects here are being built at 1/10th the speed of projects in China, but at the same (or possibly less) quality?
China's record is no better: Shoddy Construction on China’s High-Speed Railway Exposes Systemic Problems
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  #3291  
Old Posted Sep 26, 2018, 9:58 PM
mt_climber13 mt_climber13 is offline
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Quote:
Originally Posted by Busy Bee View Post
People just need to calm down. It's probably a one off minor defect that's easily remedied that's not indicative of some sort of massive structural miscalculation.
Wrong again.
Second crack has been found.
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  #3292  
Old Posted Oct 1, 2018, 7:50 PM
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Quote:
SF builders struggle to keep transit center from rising
Matier & Ross | on October 1, 2018

Its neighbor, the Millennium Tower, might be sinking, but — get this — the new $2.2 billion Transbay Transit Center has the potential to go in the opposite direction. One of the main challenges the builders faced was keeping the three-block-long monster from rising . . . .

According to the Transbay’s website, “Unlike adjacent high-rises that generally have foundations anchored into bedrock to keep from sinking, the transit center’s foundation must keep the building from floating up.”

The reason is that unlike the 58-story-tall Millennium, which has all of its weight bearing down on a half-block base, the transit center is akin to taking the Millennium and laying it down on its side.

In effect, the transit center is like a 1,500-foot-long barge floating atop a lake of deep mud . . . .

“For that reason, we did not go to bedrock,” as you would with a high-rise, Zabenah said.

Instead, the building is tied down — held in place — by 1,896 eighty-foot-long anchors embedded in the mud.

Asked whether the beams could crack because the transit center might be rising, Zabenah said: “No, it’s a localized issue” happening only above ground . . . .
https://m.sfgate.com/bayarea/matier-...p?t=c4488d053d
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  #3293  
Old Posted Oct 1, 2018, 8:27 PM
david_h david_h is offline
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How to hold up a $2 billion bus station...

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  #3294  
Old Posted Oct 2, 2018, 2:18 AM
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^^^
Heres more pics from Bigge--



Bigge Crane - https://twitter.com/BiggeCrane/statu...91761044340736
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  #3295  
Old Posted Oct 2, 2018, 5:11 AM
digitallagasse digitallagasse is offline
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Originally Posted by Pedestrian View Post
I say this with no knowledge as to the engineering involved for this. Wouldn't it have been better to anchor the building to bedrock? If a building was anchored to bedrock that should stop a building from sinking or rising. Dirt isn't that solid and even more so with earthquakes in play. Like Millennium Tower this feels like a cost savings design.
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  #3296  
Old Posted Oct 2, 2018, 7:30 AM
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Originally Posted by digitallagasse View Post
I say this with no knowledge as to the engineering involved for this. Wouldn't it have been better to anchor the building to bedrock? If a building was anchored to bedrock that should stop a building from sinking or rising. Dirt isn't that solid and even more so with earthquakes in play. Like Millennium Tower this feels like a cost savings design.
Well I'm not an engineer either but the article specifically says that the engineer who was describing the situation said, "No". What they did was a more effective method and it makes sense to me. Piles going TO bedrock are just that--they go to it but aren't ATTACHED to it. In the case of Oceanwide Center, for example, they drilled 60+ ft holes into the bedrock and poured concrete, with reinforcing rod, into those holes and into caissons to the surface creating a piling plugged into the rock, but it isn't actually attached to the rock and there's nothing, really, to keep the pilings from pulling out of the holes in the rock if the structure to which they are attached were floating.

As to what they did, I am thinking of a giant version of the sort of mushroom anchor ships, with which I am familiar (after 26 years in the Navy), use on a very muddy bottom:


https://www.firstchoicemarine.com/g-1-anchor-guide.aspx

These can hold very effectively and especially the version without the holes in it that the one shown has can use suction to keep it from moving upward once it sinks into the mud.
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  #3297  
Old Posted Oct 2, 2018, 8:04 AM
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Good news, the second floor is almost entirely leased up.

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  #3298  
Old Posted Oct 2, 2018, 10:02 AM
mwhite3182 mwhite3182 is offline
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Quote:
Originally Posted by david_h View Post
How to hold up a $2 billion bus station...

... and park, and shopping center, and eventually train station. Besides, what’s wrong with bus transportation?
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  #3299  
Old Posted Oct 2, 2018, 4:58 PM
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Heres what I gathered...
Seems in those articles (to me at least) they're alluding to tiedowns but that isn't the case. Tiedowns would pull the structure down (as its name suggests)... but here they used micropiles which aren't tensioned and just basically act like driven piles (like they used on Millenium)... Transbay's foundation system is what the builders for Millenium were aiming for. I'm sure they would have used driven piles at Transbay if it wasn't for the cross bracing for the excavation... noise was probably a concern too. Because of the ability to spread the load out over 3 blocks the ability to use a foundation system that relied on friction to anchor was feasible.

This video was filmed at Transbay in 2012--
Video Link


In March 2014 newsletter they actually explained the micropiles and how they're constructed. Page 5-- https://tjpa.org/uploads/2014/04/Spr...Newsletter.pdf

More info on micropiles (the 2 pictures at the bottom appear to actually be at Transbay)-- https://drilltechdrilling.com/servic...ns/micropiles/
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  #3300  
Old Posted Oct 2, 2018, 5:27 PM
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Quote:
Holes Cut in Steel Beams Led to Cracking at San Francisco's Transbay Terminal: Engineers
By Jaxon Van Derbeken

Published at 6:06 PM PDT on Oct 1, 2018 | Updated at 11:39 PM PDT on Oct 1, 2018

Engineering experts tell NBC Bay Area the cracks found in the Transbay Terminal superstructure appear to have started at the sharp corners of holes cut into vital steel beams during construction – edges long understood to heighten stresses in any steel structure.

“It’s not a good structural element,” says mechanical engineer Bernard Cuzzillo, referring to rectangular notches clearly cut in the four-inch thick steel at the bottom of the 85-foot long I-beam used to support the terminal deck across Fremont Street.

Cuzzillo referred to one of the holes visible in the 2.5 foot wide strip, or flange, where a vertical steel plate is attached to the I-beam. “To have a hole right there creates a weak spot right where the force is greatest,” says Cuzzillo, who studies why such massive structures fail.

In fact, enhanced photos appear to show at least one of the cracks started at one of those sharp-edged corners. Normally, such edges would be rounded to prevent stresses from being concentrated at the corners, the engineers say. It is not clear why the corners were not rounded in the Transbay project or what was their intended purpose . . . .
https://www.nbcbayarea.com/news/loca...494862071.html
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