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re: San Francisco's Millennium Tower is leaning, sinking and now cracking
Posted on 9/6/18 at 1:19 pm to VABuckeye
Posted on 9/6/18 at 1:19 pm to VABuckeye
quote:
What are they going to do? Mud jack a tower?
If only there were some free material lying around on the sidewalks that could be used for this purpose. And if that material was also a nuisance that needed to be cleaned up anyway, well then that’s 2 birds with 1 stone.
0
Posted on 9/6/18 at 1:21 pm to eatpie
Depends if the architect is left or right handed.
Posted on 9/6/18 at 1:25 pm to Darth_Vader
quote:
San Francisco's Millennium Tower is leaning, sinking and now cracking
Probably because of all the poo.
Posted on 9/6/18 at 1:25 pm to CarRamrod
quote:
In addition to significant innovations above grade, the tower's below grade solution is also challenging. A tower of this height creates a higher bearing pressure below the core (14,000 psf). To provide support for such a high concentration of force, 950 14-inch square precast piles were used. While overturning due to earthquake is a significant factor, the number of piles was governed by gravity design. In order to provide a high-confidence against a possible foundation shear failure, vertical shear reinforcing is added in the 10 ft thick pile cap.
The project's five-story basement extends 75 feet below grade, nearly 45 feet below the site's water table. This open cut required special waterproofing. A unique shot-crete mixture containing Caltite is employed at perimeter walls, eliminating the need for a conventional adhered waterproofing membrane.
The foundation supports two very different types of structures. Overtime, the building is expected to settle as much as 5". The two towers are separated by a horizontal joint, and hinge slabs connect the two structures allowing for additional settlement to occur. The area between the towers, supports only three levels above grade and requires tie-downs to resist the hydrostatic uplift at the bottom of this deep excavation.
LINK
Posted on 9/6/18 at 1:27 pm to pjab
How soon before all the tenants abandon the building. Sounds like massive liability if you force employees to work in a building known to have structural problems.
Posted on 9/6/18 at 1:27 pm to NYNolaguy1
quote:Assumed? There was a geotechnical investigation done prior to design that would've provided the bearing capacities. And I'm sure it's a deep foundation system, anyway, so it's not bearing directly onto the soil just below the slab.
They assumed a very high bearing capacity on soil that most likely cant take it.
Posted on 9/6/18 at 1:29 pm to Grit-Eating Shin
quote:what if bedrock isnt very deep?
Very deep piles, I would assume.
This post was edited on 9/6/18 at 1:33 pm
Posted on 9/6/18 at 1:31 pm to CarRamrod
quote:Well then they'd obviously only be as deep as that allows.
what id bed rock isnt very deep?
Posted on 9/6/18 at 1:35 pm to Grit-Eating Shin
quote:
There was a geotechnical investigation done prior to design that would've provided the bearing capacities. And I'm sure it's a deep foundation system, anyway, so it's not bearing directly onto the soil just below the slab.
If you have ever read a geotech report, you have read an assumed value calculated by a geotech engineer using data collected by borings, augers, and various equations.
Posted on 9/6/18 at 1:36 pm to CarRamrod
quote:
what if bedrock isnt very deep?
Building on bedrock is an accepted building practice.
Posted on 9/6/18 at 1:38 pm to NYNolaguy1
quote:did i say it wasnt?
Building on bedrock is an accepted building practice.
Posted on 9/6/18 at 1:39 pm to PearlJam
I think the new train terminal was built near it.
But the foundation issues were apparent before that really started happening.
But the foundation issues were apparent before that really started happening.
Posted on 9/6/18 at 1:40 pm to CarRamrod
quote:
did i say it wasnt?
No
.Posted on 9/6/18 at 1:41 pm to SoFla Tideroller
quote:
How soon before all the tenants abandon the building. Sounds like massive liability if you force employees to work in a building known to have structural problems.
It features a lot of residential...
...most of it very expensive housing.
Posted on 9/6/18 at 1:44 pm to member12
quote:
I think the new train terminal was built near it.
But the foundation issues were apparent before that really started happening.
This. It was settling before they started the building process on the new terminal.
Maybe they should have gone down to bedrock?
quote:
The foundation of the main tower is a concrete slab built on 60–90-foot-deep (18–27 m) concrete friction piles through the fill and Young Bay Mud, and embedded into dense Colma sand. A number of other buildings in 301 Mission Street’s area have used similar systems, although due to varying earth conditions, others have pushed piles directly into the bedrock 200 feet (61 m) below.[
Posted on 9/6/18 at 1:44 pm to PearlJam
Yes,
Mark Benioff and Salesforce built a brand new building near it. Many blame them for this.
Mark Benioff and Salesforce built a brand new building near it. Many blame them for this.
Posted on 9/6/18 at 1:48 pm to NYNolaguy1
quote:If I ever have?
If you have ever read a geotech report
Only about a hundred. It's not really "assumed" if it's based on the actual mechanical properties of the soil, but I don't want to hijack the thread with semantics. There is a myriad possible reasons that this tower is having issues, and we can only speculate about the cause. Posted on 9/6/18 at 1:50 pm to Darth_Vader
I'd think you would have more than 1 window cracked if it was from pressure because of the building leaning.
Posted on 9/6/18 at 1:52 pm to Darth_Vader
Add to that their radical liberal leadership, rampant homelessness, and failing subway system that will have to have miles of steel replaced because it was the wrong grade steel and you've got pretty lame city.
Posted on 9/6/18 at 1:53 pm to bbrownso
quote:
The foundation of the main tower is a concrete slab built on 60–90-foot-deep (18–27 m) concrete friction piles
Sounds like they didn't drive piles to refusal.
quote:
A number of other buildings in 301 Mission Street’s area have used similar systems, although due to varying earth conditions, others have pushed piles directly into the bedrock 200 feet (61 m) below
Assuming the bedrock is just as deep at this site, they built a very heavy building on top of piles that were not driven to refusal at bedrock depth. They're relying on sand. I'm no structural engineer, but with the weight of the tower bearing down on the soil like that, you have to wonder what the thought process was here.
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