CHICAGO | 1000M (1000 S Michigan) | 805 FT | 73 FLOORS - Page 105

harryc · #**2081** Posted **Jan 18, 2022, 9:10 PM**

Quote:

Originally Posted by BuildThemTaller

It took them a long time between pouring caisons to building above ground level. Might be the longest wait between those two stages, come to think of it.

Hold my beer ......

January 2008

rivernorthlurker · #**2082** Posted **Jan 18, 2022, 9:32 PM**

Quote:

Originally Posted by harryc

Hold my beer ......

January 2008

Well Played.

Drcastro · #**2083** Posted **Jan 19, 2022, 12:50 AM**

Quote:

Originally Posted by thegoatman

This thing is going up fast, looks like they're already working on the first floor. Will be a great addition to the michigan ave wall and fill in the sloop skyline.

Caisson work started in November 2019.

kolchak · #**2084** Posted **Jan 19, 2022, 10:10 PM**

Today -

sentinel · #**2085** Posted **Jan 19, 2022, 10:30 PM**

It's moving along nicely - somewhat bittersweet, but happy that Jahn's last major project is here in Chicago.

BVictor1 · #**2086** Posted **Jan 19, 2022, 11:25 PM**

Do we have a date/day on the mat pour? Anything?

Fvn · #**2087** Posted **Jan 19, 2022, 11:33 PM**

Quote:

Originally Posted by BVictor1

Do we have a date/day on the mat pour? Anything?

Seems like it could be this weekend...looks really close to being ready

Drcastro · #**2088** Posted **Jan 20, 2022, 6:40 AM**

Wow, the amount of rebar in that mat is insane! I’m not used to seeing something like that basically at-grade.
Does anyone have any idea how many layers of it are in there?

r18tdi · #**2089** Posted **Jan 20, 2022, 3:40 PM**

Quote:

Originally Posted by Fvn

Seems like it could be this weekend...looks really close to being ready

My money is on this weekend.

Fvn · #**2090** Posted **Jan 20, 2022, 3:47 PM**

Quote:

Originally Posted by Drcastro

Does anyone have any idea how many layers of it are in there?

Rebar mats like this are actually pretty "hollow" since all rebar structures are generally massive cages. The reinforcement cage for a mat foundation consists of a thicker layer of rebar on the bottom and the top with supporting bars to hold the top layer up/tie the layers together. The ends of the top and bottom bars are also bent at 90 and then tied together with additional bars which makes it even more like a cage. A mat like this could only have 10 actual layers of rebar.

Structure Magazine

ardecila · #**2091** Posted **Jan 20, 2022, 5:32 PM**

Quote:

Originally Posted by Fvn

Rebar mats like this are actually pretty "hollow" since all rebar structures are generally massive cages. The reinforcement cage for a mat foundation consists of a thicker layer of rebar on the bottom and the top with supporting bars to hold the top layer up/tie the layers together. The ends of the top and bottom bars are also bent at 90 and then tied together with additional bars which makes it even more like a cage. A mat like this could only have 10 actual layers of rebar.

Yeah the greatest forces on a horizontal element (like a beam or a foundation) are always concentrated at the top and bottom so that's where you put the reinforcement.

It's also why I-beams have heavy top and bottom plates and a pretty thin web connecting them, and you can even cut holes in the web without affecting the strength (note: don't try this at home, kids).

harryc · #**2092** Posted **Jan 20, 2022, 6:49 PM**

Quote:

Originally Posted by ardecila

Yeah the greatest forces on a horizontal element (like a beam or a foundation) are always concentrated at the top and bottom so that's where you put the reinforcement.

It's also why I-beams have heavy top and bottom plates and a pretty thin web connecting them, and you can even cut holes in the web without affecting the strength (note: don't try this at home, kids).

My understanding is that the mat is supporting a load - both compression and tension - but principally compression.

While Steel is best for both as far as capability, a thicker concrete section will take as much load at a fraction of the cost of steel. The concrete sucks at tension, really sucks, so where the load will be compression only they use concrete, where you expect tension you use steel. In most foundation slabs the tension is transferred to the outside, thus lots of steel on the top and bottom.

( corrections and clarifications welcome and appreciated )

r18tdi · #**2093** Posted **Jan 21, 2022, 5:02 PM**

From McHugh:

Quote:

"Our team has already erected the tower crane, installed the utility piping to run through the mat, placed the waterproofing, and is working on installing the 12 layers of rebar for the mat. When completed, the mat slab will be 11'6" deep under the entire building core, with a total of 3,890 cy of concrete! 200cy of it will be used for the elevator pits and the remaining 3,690cy will be poured monolithically. This process will take approximately 13 hours and the concrete will be delivered by 410 trucks!"

https://www.instagram.com/tv/CY9fkXFp0rJ/

BrinChi · #**2094** Posted **Jan 21, 2022, 7:19 PM**

Wow 410 trucks over 13 hours works out to each truck getting in, dumping its load, and out in under 2 minutes? Anyone know how they do this?

PittsburghPA · #**2095** Posted **Jan 21, 2022, 7:32 PM**

Quote:

Originally Posted by BrinChi

Wow 410 trucks over 13 hours works out to each truck getting in, dumping its load, and out in under 2 minutes? Anyone know how they do this?

My guess would be several trucks at once.

sentinel · #**2096** Posted **Jan 21, 2022, 8:36 PM**

Quote:

Originally Posted by BrinChi

Wow 410 trucks over 13 hours works out to each truck getting in, dumping its load, and out in under 2 minutes? Anyone know how they do this?

It's Friday, the end of a stupid stressful work week (don't go into architecture, kids. Stick with finance. Or IT), so I'm gonna pass up on the opportunity to make any kind of tastless porn analogy.

But yes, that does seem insane...I wonder if the cold weather is forcing them to pour the concrete quickly so it doesn't cure improperly..but I suspect they've already accounted for that.

BVictor1 · #**2097** Posted **Jan 21, 2022, 9:28 PM**

The pour is tomorrow.

bhawk66 · #**2098** Posted **Jan 21, 2022, 9:48 PM**

Is there any temperature threshold at all when it comes to pouring concrete in the cold?
21 degrees to start the day tomorrow. I know curing concrete generates heat, but I'd think there has to be a limit, no?

F1 Tommy · #**2099** Posted **Jan 21, 2022, 10:12 PM**

They poured 150 North Riversides when it was 20 below zero. I remember it was steaming due to the additives added to the concrete mix.

Fvn · #**2100** Posted **Jan 21, 2022, 11:43 PM**

Quote:

Originally Posted by bhawk66

Is there any temperature threshold at all when it comes to pouring concrete in the cold?
21 degrees to start the day tomorrow. I know curing concrete generates heat, but I'd think there has to be a limit, no?

Temperature definitely is a factor but advancements in admixtures have made it so that you can do massive pours like this in the cold. The process of making concrete actually produces quite a bit of heat due to the chemical reaction taking place so you can adjust this with admixtures. During the summer, down south, they've started adding liquid nitrogen to keep it cool.

The pour will also be covered in blankets (insulation between 2 layers of tarp) once they're done which will continue to allow it properly cure in the cold; sometimes they have heating elements inside, sometimes in they don't.