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

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Could someone explain what a "shear wall" is, what they do, and how to identify them in the construction so far? One of the workers told me that the big brown iron "wall" (looks like solid iron, about 15' high and 30'long, bristling with lots of bolts - see it on the mid-left side of photos #4647 and #4649 above - extending from the Franklin Street side of the pit toward the yellow concrete pump assembly) is one of four in the building. (Earlier in the excavation, "shear wall" and an arrow were spray-painted in red on the upper level of the pilings on the Franklin Street wall of the pit).
 
Shear walls are crucial to resisting lateral loads. Without shear walls, the building would twist and fall over. Concrete elevator/stair cores act as natural shear walls in a structure, but others are often needed for stability based on shape and height (which impacts the wind loading on the tower). In a steel-framed structure, K or X bracing can accomplish this, but in a concrete structure, you just quite literally build a concrete wall the height of the tower. Most of the interior walls will be just steel stud partition walls, but there will be 4 actual concrete walls.

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I have a bunch of notes in my notebook from Structures I & II that I can add when I get home today.

I marked up a plan of Millennium Tower from the NPC showing the (non-core-related) four shear walls (highlighted). The wind is in blue.

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Gromit said:
One of the workers told me that the big brown iron "wall" (looks like solid iron, about 15' high and 30'long, bristling with lots of bolts - see it on the mid-left side of photos #4647 and #4649 above - extending from the Franklin Street side of the pit toward the yellow concrete pump assembly) is one of four in the building.
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What you are seeing is the just the forms used for building a vertical reinforced concrete wall. Once the wall is poured the forms will be stripped and it will look like the wall on the right hand side of the picture.
 
datadyne007 said:
Concrete elevator/stair cores act as natural shear walls in a structure, but others are often needed for stability based on shape and height (which impacts the wind loading on the tower). In a steel-framed structure, K or X bracing can accomplish this, but in a concrete structure, you just quite literally build a concrete wall the height of the tower. Most of the interior walls will be just steel stud partition walls, but there will be 4 actual concrete walls.
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I would add that:
(1) the elevator/stair and mechanical 'cores' are designed to "act that way" because they are a convenient place in the layout of an office building to place uniform width uninterrupted reinforced concrete walls. Small areas in walls can be interrupted for elevator & stair door openings and mechanical shafts but this complicates the design.

(2) Steel bracing usually is a simple diagonal between two floors, but short floors with long bays typical in a residence make K or X bracing better options.

(3) The location of the lateral system is typically driven most critically by building type (office /residential), layout, height and mass / floor area. Secondarily construction schedule and technique and fire codes will affect this choice.
 
I will also add to this:

Architects hate shear walls, they get in the way of ... everything. :)

Everything in the world should be a moment frame.

cca


(just kidding of course)
 
Not to derail the thread, but can someone please explain to me how a tower goes from an idea, to being ready to be built? I am not talking about acquiring land, or the necessary financing. I mean when a developer wants to build say an 800 foot tower, what's the process from the idea, to the actual design, to the point where it's ready to actually be built. How long does the whole process take?

I only ask because it's apparent there are several posters who know what they're talking about when it comes to design and construction.
 
DBM said:
My understanding is that the developer has entered into a maintenance agreement with the BRA/PWD to maintain in perpetuity the Summer St. Plaza pavers which are currently being put down... thus, I suspect you are quite mistaken [if only for an exceptional reason].
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I just walked the part that they recently finished and opened up to foot traffic. Maybe there is still work to be done on the part they just "finished" by oh my does it already look and feel crappy for something that is merely days old. It is already uneven in places.
 
BosDevelop said:
I just walked the part that they recently finished and opened up to foot traffic. Maybe there is still work to be done on the part they just "finished" by oh my does it already look and feel crappy for something that is merely days old. It is already uneven in places.
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I am reminded of an urban design class I had year's ago. The prof was showing pictures of new crosswalks around Christopher Columbus Park, that used cobblestones for the crossings. He was lauding how great the cobblestones were to clearly delineate the pedestrian crossings.

We pointed out that in all the pictures, the pedestrians, to a person, were avoiding walking on the cobblestones. They were walking AROUND the crosswalks.
 
DBM said:
My understanding is that the developer has entered into a maintenance agreement with the BRA/PWD to maintain in perpetuity the Summer St. Plaza pavers which are currently being put down... thus, I suspect you are quite mistaken [if only for an exceptional reason].
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This is probably true. I was told by PWD that these days they do require a maintenance agreement when non-standard materials are used on the public way.

commuter guy said:
Due to some state law or local ordinances the utilities don't put things back to square one and/or reconstruct the impacted area, but rather pay into some fund to the affected local town or state in lieu. The idea is the town will use those proceeds for repaving etc.
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Fun fact. In Melrose, they recently changed their excavation permits to require much better patches. If the trench is in some proximity (don't remember the exact measurement) to any of their older patches, they need to repave both. They are also required to repave no less than half the roadway width. You can see an example of this in the following link. I believe this was after a gas line replacement. http://goo.gl/maps/QqyqS
 
mass88 said:
Not to derail the thread, but can someone please explain to me how a tower goes from an idea, to being ready to be built? I am not talking about acquiring land, or the necessary financing. I mean when a developer wants to build say an 800 foot tower, what's the process from the idea, to the actual design, to the point where it's ready to actually be built. How long does the whole process take?

I only ask because it's apparent there are several posters who know what they're talking about when it comes to design and construction.
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This would take many many pages of text to talk about. I have some experience with tall projects so the shortest possible answer I can give you is, it could take somewhere between 5 and 10 years of design and construction. There are always cases of quicker and slower. I would be happy to help answer any specific question you might have regarding the design process. PM me so the thread is not derailed.

cca
 
Is the ceiling in those renderings the exposed brick or clay tile that's visible in some of the renovation pictures a few pages back?
 
^Yes. That picture has me confused, because it looks like masonry, but it's not vaulted.
 
My guess is that it was originally tiled but all the tile has been removed and we are looking at the 'ghosts' (grout lines, etc...) of the old tile.
 
chumbolly said:
Is the ceiling in those renderings the exposed brick or clay tile that's visible in some of the renovation pictures a few pages back?
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Whatever it is, it's original to the building. I noticed it when they first opened up the first floor, and wondered whether it would be replaced since it looked so ratty. I guess ratty-looking won't matter when it's covered by a drop ceiling...
 
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