State Street HQ | One Congress | Bulfinch Crossing | West End

From MGH
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Looking through the steel skeleton up close in the last pic,, I see no evidence of a concrete core. How can this continue to happen after 09-11? 🥺
 
Jahvon09 said:
Looking through the steel skeleton up close in the last pic,, I see no evidence of a concrete core. How can this continue to happen after 09-11? 🥺
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..... You can see it protruding from the top, right between the cranes.

And in the hundreds of photos taken in the past year on this forum clearly showing the core go up....
 
Jahvon09 said:
I can see it on the top of the tower, but it is hard to see it inside.
Click to expand...

Really?

State Street HQ | One Congress | Bulfinch Crossing | West End

5/8 from Malden (note I put up an angle never before seen on archboston in post 939, but it looks like it got buried). I wonder if any of MT will be left showing from here once this is done? IMG_8785 by David Z, on Flickr IMG_8788 by David Z, on Flickr IMG_8790 by David Z, on Flickr...
archboston.com
 
Jahvon09 said:
Looking through the steel skeleton up close in the last pic,, I see no evidence of a concrete core. How can this continue to happen after 09-11? 🥺
Click to expand...
It is difficult to see the core through the steel framing, but if you go through the earlier construction pics you can see the core rise up with building, so no need to worry! :)
 
I saw them. Thanks. It DOES look like there isn't a concrete core through the steel. It threw me off. :(
 
Wow! Awesome pics of State Street plus the added bonus of great views of the North End, the North Station area, and Downtown. Thanks kz.
 
I'm generally just a lurker on these pages but now I'm curious, as someone who knows nothing about construction other than what I've seen in photos on here. Is a concrete core a relatively new construction practice that was implemented after 9/11? What is its purpose? I had assumed that it was just where a building's elevators were housed and that it was just "how it's done." Is there more to it? Is there some federal requirement that any building over X stories needs to have one?
 
crispino said:
I'm generally just a lurker on these pages but now I'm curious, as someone who knows nothing about construction other than what I've seen in photos on here. Is a concrete core a relatively new construction practice that was implemented after 9/11? What is its purpose? I had assumed that it was just where a building's elevators were housed and that it was just "how it's done." Is there more to it? Is there some federal requirement that any building over X stories needs to have one?
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Avalon North Station and Verizon building don't have concrete cores so I assume it's not a requirement.
 
crispino said:
I'm generally just a lurker on these pages but now I'm curious, as someone who knows nothing about construction other than what I've seen in photos on here. Is a concrete core a relatively new construction practice that was implemented after 9/11? What is its purpose? I had assumed that it was just where a building's elevators were housed and that it was just "how it's done." Is there more to it? Is there some federal requirement that any building over X stories needs to have one?
Click to expand...
Not an engineer, but:
Concrete cores are good at providing shear support against lateral forces. That is, if you build a steel structure where all the joints are at right angles, there's little to prevent lateral forces from pushing those rectangles sideways into parallelograms. A concrete wall won't get pushed sideways into a parallelogram because it's a solid plane. So it makes sense to build solid concrete walls up the middle of building to provide shear support and then attach right-angle steel framing to it, with the core preventing the right-angle steel joints from twisting.

If you don't have concrete "shear walls" then you need to add in angle-bracing to provide the shear support. A right-angle square can get pushed into a parallelogram, but not if it has diagonal bracing that basically creates the hypotenuse of a right triangle inside the square. Plenty of steel structures do this instead of using a concrete core, but it's more complicated and often costlier than just putting up concrete. But concrete is way heavier than steel, so if you're adding new floors on top of existing ones (like at Avalon North Station or the office component of Hub on Causeway) it often makes sense to use steel angle bracing instead of concrete for shear support. You'll also probably see steel angle bracing at the air rights project by Lansdowne Station for the same reason.

There are building codes and standards requiring certain levels of shear support, but these can be met with concrete shear walls or with steel angle bracing. It's just a question of which works better for your project, and with built-from-scratch towers on terra firma, a concrete core is usually the cheaper and easier way to go.

Concrete is also good in the case of fires, but you can meet fire standards with properly designed steel too.
 
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