Millennium Tower (Filene's) | 426 Washington Street | Downtown

[Jahvon09]

I don't know of any other tall skyscraper in Boston that was made completely of rebar concrete. Unless it were the twin Sheraton Hotel towers over at the Pru Center.

 

[markhb]

Regarding SF: "301 Mission St. was never designed, expected, advised or required to drill pilings ‘200 feet down to bedrock.’ "

Ohh kayy..... let the acrimony and finger pointing commence! Just so long as none of these topple over on me the next time I'm at the Moscone for a conference.

On-topic: damn, the Boston MT is beautiful. Too bad I'm not the guy in NH who just hit Powerball.

 

[bigpicture7]

Millennium Tower Boston has a 6'-6" thick mat slab foundation with 24.3 million pounds & 6,000+ cubic yards of concrete. It was the largest continuous concrete pour in the history of Boston.

Yes, but did they include piles to the bedrock that's supposedly only ~45ft beneath MT? Not saying they needed to - plenty of successful mat slabs out there, but if they did, I would think it would immediately put any questions about boston's MT to bed.

 

[stellarfun]

There is bedrock, and then there is bedrock.

Under most of downtown Boston is the Cambridge Formation, called Cambridge Argillite (also called Cambridge Slate or Cambridge Mudstone, depending on which geologist you are talking with). The argillite is a slightly metamorphosed, reasonably weak, layered sedimentary rock.

An interesting survey on the use of Roxbury puddingstone as a facade material in Boston.
http://written-in-stone-seen-throug...chitectural-geology-of-boston-roxbury_27.html

 

[bigpicture7]

There is bedrock, and then there is bedrock.

Agreed, but I am willing to bet that any bedrock (puddingstone or otherwise) is better than the "dense sand" that the SF MT's stubby little piles are sitting in. Any geotechnical engineers out there?

 

[stick n move]

Off topic but I think i remember the Burj Khalifa just used a shit ton of deep pilings into the sand to hold up the building without touching bedrock. So its common and safe I think they just fucked this one up.

 

[Jahvon09]

As long as the building is safe, and there was no crappy construction.

 

[stellarfun]

In fact, the Millennium Tower sits on an area of mud-fill. It is not steel-framed, and instead relies on shear walls, columns and beams. The building is anchored over a thick concrete slab and its pilings extend about 80 feet into dense sand, not into the bedrock which lies about 200 feet below street level.

For that reason, the transit authority says it went to considerable expense to protect its high-rise neighbor, before it even broke ground on the Transbay Terminal.

“Aware that the Millennium Tower foundation failed to reach bedrock and was therefore inadequate to support the Tower, the TJPA took the extraordinary step of spending more than $58 million to install an underground buttress between the Millennium Tower and the Transit Center site before the TJPA began its excavation for the new Transit Center,” the statement said, denying any responsibility for the settlement of the Millenneum Tower.

In earthquake-prone Northern California, the sinking is raising major concerns.

http://sanfrancisco.cbslocal.com/20...y-high-rise-millennium-tower-is-sinking-fast/

 

[Jahvon09]

I went by there today and noticed what appeared to be a crack in one of the lower floor window panes taped up.

How tacky is that for a new tower that still has yet to open for business. Shame!

 

[617]

I went by there today and noticed what appeared to be a crack in one of the lower floor window panes taped up.

How tacky is that for a new tower that still has yet to open for business. Shame!

Maybe it's sinking?

 

[stefal]

 

[Jahvon09]

Maybe it's sinking?

Sort of reminds me of the Hancock Place Tower when it opened for business. The window panes kept on popping out and falling to the street below.

Watchmen were put on duty to warn passersby and watch for anything falling from the tower.

Turns out that the building was swaying to the point where the panes would fall out! Structural engineers had to install a sliding damper near the top of the building to greatly reduce or eliminate swaying of the tower.

 

[bobthebuilder]

I went by there today and noticed what appeared to be a crack in one of the lower floor window panes taped up.

How tacky is that for a new tower that still has yet to open for business. Shame!

Is it really that big of a deal? That can happen any time whether this building was open or not.



To your point on the Hancock, there are actually two tuned mass dampers (one on either end) to counteract the twisting motion of the building.

 

[bigpicture7]

For those interested in Boston Millenium Tower's foundation system and how it might compare to SF MT's:

Boston MT's geotechnical firm was Hayward Baker. They have an article on all of the site prep, excavation, foundation design (and even tower crane support design):

Boston Millenium Tower Geotechnical Design

"Ground improvement was required because the native bearing soils were previously disturbed below the bottom of the proposed mat foundation. Without ground improvement, the mat foundation would settle beyond tolerable limits. Hayward Baker was able to design and install an auger cast soil replacement prior to excavation and in conjunction with ongoing construction activities with minimal impact to construction schedule. Figure 4 shows Hayward Baker auger cast drill rig during ground improvement operations. Once excavation and ground improvement was completed, construction of the building’s 6-foot thick reinforced concrete mat could begin
...
For support of the tower crane, Hayward Baker installed 150-ton capacity micro piles extending through the fill, clay and into bedrock with a length of approximately 100 feet. Micro pile installation was performed at night to limit disruption on the project schedule."

EDIT So Boston MT's 6'+ reinforced concrete mat is supported by auger-castings, as such, beneath the mat:

 

[datadyne007]

^ Great investigative work! Very interesting. I thought I remembered them drilling shafts first.

They specifically identified the fact that the mat slab would settle too much without the supports and corrected it. Good stuff.

Without ground improvement, the mat foundation would settle beyond tolerable limits.

 

[Money]

So the first figure bigpicture posted from the website shows an area annotated as "approximate area of ground improvements" that is maybe 1/12 of the total area of the building footprint. Are we sure that these auger castings were placed across the whole foundation, or does it not matter? Sorry for belaboring things...just looking for a little foundation edification.

 

[Equilibria]

For those interested in Boston Millenium Tower's foundation system and how it might compare to SF MT's:

Boston MT's Geotechnical design firm was Hayward Baker. They have an article on all of the site prep, excavation, foundation design (and even tower crane support design):

Just for clarity, MT San Francisco had a different geotech consultant: Treadwell and Rollo.

http://www.treadwellrollo.com/files/FileUpload/67/Millennium Tower.pdf

115 Federal would have a different one than either of them - Haley and Aldrich.

 

[Jahvon09]

Is it really that big of a deal? That can happen any time whether this building was open or not.



To your point on the Hancock, there are actually two tuned mass dampers (one on either end) to counteract the twisting motion of the building.

Can't help what I notice.

I'm pretty sure that it will be repaired or replaced. Just like the plywood panels next to it.

 

[bigpicture7]

So the first figure bigpicture posted from the website shows an area annotated as "approximate area of ground improvements" that is maybe 1/12 of the total area of the building footprint. Are we sure that these auger castings were placed across the whole foundation, or does it not matter? Sorry for belaboring things...just looking for a little foundation edification.

Ah good point - that thing was so grainy I didn't catch it. I've edited my prior post to remove the "all over the place." However, one would hope they took a whole bunch of cores and figured out where these things needed to go.

It's just interesting to see that, at least from what it seems, these 2 (and now 3) Millennium projects had different Geotech teams and possibly employed different foundation systems.

 

[bigpicture7]

^ OK, just a little more homework to round this out:

It appears that the exploratory geotech consulting work for the 1 Franklin MT was done by Haley and Aldrich (ref. 2012 NPC), and at that time they also mention the drilled foundation elements.

I'm sure the full drawing set has more detail on where the drilled shafts are actually located.