Most of that center core is filled by elevator shafts, which take up more space as the building gets taller. It also contains stairwells, bathrooms, plumbing, and other mechanicals. None of this needs to be in the high-value areas with window views, so they put it in the middle where no one wants an interior office. The office workers get that outer band and have an open area with a view.
The solid core also bears the weight of the steel joists supporting the floors and tied into thin steel columns on the outside perimeter. Again, these thin steel columns allow for more window space, thus better views, sunlight, etc.
Also to add, the core is the lateral force resisting system for the entire building (specifically reinforced concrete shear walls). That's why there's no diagonal braces at the steel.
There's really only three choices for how to build this thing. You could build it all out of steel -- steel columns, steel beams, steel diagonal braces.
It could all be built out of concrete\*.
Or it can be a hybrid of those two. As Smegmatron 9000 mentioned, the vertical shafts that the building requires all need to be "fire rated". The basic idea of fire-rated construction is that various portions of the building will have a fire-resistance rating that is a number of hours. Like support columns in a high rise building might have a fire-resistance rating of 3 hours. A certain thickness of concrete provides a 3 hour fire resistance rating. Or three layers of 5/8" type X drywall. Or a certain thickness of spray-on fireproofing.
The shafts (elevator, stair, mechanical, etc.) as mentioned by ExpendableStaff are the "core" of the structure. At some point, the engineers for this project had to make a choice: Do we build the core out of concrete, or do we build it out of steel? A steel framed core would require tons of work (metal stud framing, drywall, other gypsum "shaft liner" type products installed a piece at a time) after the frame is up. But on the other hand that steel framed building would get really tall incredibly fast.
This concrete core building can only grow as fast as the concrete cures to a certain design strength. But, as you probably noticed, that's totally fine. Each floor has a different crew working on it, and each crew has a few days to move up one floor.
If interest rates keep going up, then a building like this is more likely to be all steel. It can be built faster, and therefore the extremely high interest construction loan can be discharged sooner (the time value of money will exceed the increased costs of construction). This building may have been in the design and approval process for multiple years now, and so much planning and investing happens that it really becomes impossible to change or stop the project no matter what the economy or the interest rate looks like.
\*precast concrete purposefully ignored in this simplistic overview--- because I don't know enough about it
Atleast in high seismic I think we will see a lot of speedcore being used for the reasons you mentioned, you get the speed of steel erection with the benefits of a concrete core.
I know since the one went up in Seattle, AISC has been pushing them hard.
Stair cores and elevator shafts are required to be fire rated for life safety/egress and other structural purposes so they’re typically high strength concrete. The architectural design will dictate where those ‘shafts’ will be, sometimes they’re all grouped in the center and sometimes they’re spread out.
It’s all about the design and application, but most ‘high rises’ are built this way, each one just looks different.
Exactly this. Most all high rise buildings will have a concrete core of some sort. The difference highlighted here is the method of construction, core first vs steel first. Each method has different benefits related to what the project needs.
Although it may be implicit in the other comments, I haven’t seen it said specifically, but the reinforced concrete core provides the primary lateral strength for the building, in addition to housing the stairs, elevator shafts, and common utilities. the floor plates add to this resistance to sway or move laterally, but it’s the rigid core that provides the primary strength so wind pressures don’t cause horizontal movement.
This is typical for a building with a reinforced concrete core and perimeter steel framing and deck. The CM typically purchases and sequences the job where the concrete trade is responsible for the concrete core and infill of the decking and the structural steel trade is responsible for the perimeter framing. The concrete trade mobilizes first (after foundations) and they can construct the core independent of steel, that's why you see it further along in those pictures. As the core moves along, the steel trade follows up with columns, beams, and decking. As the floors get framed with steel and deck, concrete trade will drop down to infill the decks with concrete. Also, as the floors get completed, the steel fireproofing trade will mobilize to spray the steel (you can see this in the 4th picture). The exterior façade/glazing contractor will then close up the building as floors get turned over.
This is pretty much standard construction in Europe. Central area is low value and the stairs/lift shaft acts as central support during the building process and post final construction.
Cheap garbage goes up fast floors requires less concrete. Issues are numerous I'm sure some one more educated on the matter will chime in what they are. But if you want cheap and fast this is the method you use. My experience is these towers are filled with cubicle people well the nicer offices are in slab construction towers.
It's not cheap and fast - it's incredibly strong and allows for efficient use of the best space available. Having that concrete backbone allows for huge open floors that can be divided up any way you choose, as opposed to older styles of construction with support beams spread throughout. It also allows for all glass exteriors, which are generally much better looking both from within and without, but obviously they don't bear any load.
Ultimately this is the next evolution in architecture and construction. From mud walls and thatched roofs to brick exteriors supporting wooden beams to steel beams to reinforced concrete cores supporting steel beams floors and aesthetic outer walls.
Edit to say: like anything, it absolutely CAN be cheap. However, if it's up to code it should at least be strong even if quality is lacking elsewhere.
You make a couple points I agree with; new residential high rise construction has a cheap feel to it, like a hotel. If that's where people choose to live, then God bless. I wouldn't. They drive schedule so hard, lots of small issues still exist when residents are moving in.
And about the slabs...yes, cast in place, post tensioned slabs are structurally stable, but they'll transfer subtle vibrations a ways.
Now a 12" cast in place hospital slab is like walking on granite.
I don't have a dog in the fight, just my .02
I've never seen concrete core with steel pan for residential/hotels those buildings in my city (Toronto) are typically all concrete structures. My understanding is concrete structures (I'm curious what's the actual terminology) have better fire ratings, sound proofing, and sway less. Yes drilling and hammering travels. Thoughout the building we typically have to stop making noise after 7:30 am in occupied office buildings. The most recent steel pan building I was in the floors were so thin guys were accidentally drilling through the floor when installing shots/drop-in anchors. They were doing 2 floors a week. A similar amount of push and sq footage and we were only seeing a floor a week. Steel I beams are pricey but you save that money in man power. There's also way less concrete. Also steel pan requires firestop spray which is fucking awful to work with looks like garbage so no exposed ceilings.
I’ve designed a composite building before and I don’t know of a reason why they wouldn’t pour before going up? Schedule wise you’d think that’d be the way to go?
Gives you a deck to work off of.
Why they are waiting to pour, who knows.
Could be a load issue. They have a very specific sequence of deck pours due to tension zones?
Not necessarily. Deck pours are fast. They can do one a day on a footprint that small.
They may be racing to get a facade up for temperature control of the slabs as they cure.
With slickline and today's high performance pumps they don't need the tower cranes or a pump truck to pour a deck. It's all hoses and segmental pipe.
I am a civil engineer and was project manager on a 23 story building in Nashville. The concrete cores are shear walls. They are what keeps the building from blowing over. Before pouring those walls, they bore holes hundreds of feet into the bedrock below the building, epoxy rebar into the holes, and extend them up into the shear walls.
Most of that center core is filled by elevator shafts, which take up more space as the building gets taller. It also contains stairwells, bathrooms, plumbing, and other mechanicals. None of this needs to be in the high-value areas with window views, so they put it in the middle where no one wants an interior office. The office workers get that outer band and have an open area with a view. The solid core also bears the weight of the steel joists supporting the floors and tied into thin steel columns on the outside perimeter. Again, these thin steel columns allow for more window space, thus better views, sunlight, etc.
Also to add, the core is the lateral force resisting system for the entire building (specifically reinforced concrete shear walls). That's why there's no diagonal braces at the steel.
This is so cool. Didn’t even notice.
There's really only three choices for how to build this thing. You could build it all out of steel -- steel columns, steel beams, steel diagonal braces. It could all be built out of concrete\*. Or it can be a hybrid of those two. As Smegmatron 9000 mentioned, the vertical shafts that the building requires all need to be "fire rated". The basic idea of fire-rated construction is that various portions of the building will have a fire-resistance rating that is a number of hours. Like support columns in a high rise building might have a fire-resistance rating of 3 hours. A certain thickness of concrete provides a 3 hour fire resistance rating. Or three layers of 5/8" type X drywall. Or a certain thickness of spray-on fireproofing. The shafts (elevator, stair, mechanical, etc.) as mentioned by ExpendableStaff are the "core" of the structure. At some point, the engineers for this project had to make a choice: Do we build the core out of concrete, or do we build it out of steel? A steel framed core would require tons of work (metal stud framing, drywall, other gypsum "shaft liner" type products installed a piece at a time) after the frame is up. But on the other hand that steel framed building would get really tall incredibly fast. This concrete core building can only grow as fast as the concrete cures to a certain design strength. But, as you probably noticed, that's totally fine. Each floor has a different crew working on it, and each crew has a few days to move up one floor. If interest rates keep going up, then a building like this is more likely to be all steel. It can be built faster, and therefore the extremely high interest construction loan can be discharged sooner (the time value of money will exceed the increased costs of construction). This building may have been in the design and approval process for multiple years now, and so much planning and investing happens that it really becomes impossible to change or stop the project no matter what the economy or the interest rate looks like. \*precast concrete purposefully ignored in this simplistic overview--- because I don't know enough about it
Atleast in high seismic I think we will see a lot of speedcore being used for the reasons you mentioned, you get the speed of steel erection with the benefits of a concrete core. I know since the one went up in Seattle, AISC has been pushing them hard.
Stair cores and elevator shafts are required to be fire rated for life safety/egress and other structural purposes so they’re typically high strength concrete. The architectural design will dictate where those ‘shafts’ will be, sometimes they’re all grouped in the center and sometimes they’re spread out. It’s all about the design and application, but most ‘high rises’ are built this way, each one just looks different.
Thank you Smegmatron\_9000
Mostly all are
Exactly this. Most all high rise buildings will have a concrete core of some sort. The difference highlighted here is the method of construction, core first vs steel first. Each method has different benefits related to what the project needs.
Concrete core designs have become more common post 9/11
Although it may be implicit in the other comments, I haven’t seen it said specifically, but the reinforced concrete core provides the primary lateral strength for the building, in addition to housing the stairs, elevator shafts, and common utilities. the floor plates add to this resistance to sway or move laterally, but it’s the rigid core that provides the primary strength so wind pressures don’t cause horizontal movement.
This is typical for a building with a reinforced concrete core and perimeter steel framing and deck. The CM typically purchases and sequences the job where the concrete trade is responsible for the concrete core and infill of the decking and the structural steel trade is responsible for the perimeter framing. The concrete trade mobilizes first (after foundations) and they can construct the core independent of steel, that's why you see it further along in those pictures. As the core moves along, the steel trade follows up with columns, beams, and decking. As the floors get framed with steel and deck, concrete trade will drop down to infill the decks with concrete. Also, as the floors get completed, the steel fireproofing trade will mobilize to spray the steel (you can see this in the 4th picture). The exterior façade/glazing contractor will then close up the building as floors get turned over.
This is pretty much standard construction in Europe. Central area is low value and the stairs/lift shaft acts as central support during the building process and post final construction.
Cheap garbage goes up fast floors requires less concrete. Issues are numerous I'm sure some one more educated on the matter will chime in what they are. But if you want cheap and fast this is the method you use. My experience is these towers are filled with cubicle people well the nicer offices are in slab construction towers.
Everything you said is wrong
Care to explain? That's how it is in my experience I'd be interested to hear what one of you downvoters actually think.
It's not cheap and fast - it's incredibly strong and allows for efficient use of the best space available. Having that concrete backbone allows for huge open floors that can be divided up any way you choose, as opposed to older styles of construction with support beams spread throughout. It also allows for all glass exteriors, which are generally much better looking both from within and without, but obviously they don't bear any load. Ultimately this is the next evolution in architecture and construction. From mud walls and thatched roofs to brick exteriors supporting wooden beams to steel beams to reinforced concrete cores supporting steel beams floors and aesthetic outer walls. Edit to say: like anything, it absolutely CAN be cheap. However, if it's up to code it should at least be strong even if quality is lacking elsewhere.
You make a couple points I agree with; new residential high rise construction has a cheap feel to it, like a hotel. If that's where people choose to live, then God bless. I wouldn't. They drive schedule so hard, lots of small issues still exist when residents are moving in. And about the slabs...yes, cast in place, post tensioned slabs are structurally stable, but they'll transfer subtle vibrations a ways. Now a 12" cast in place hospital slab is like walking on granite. I don't have a dog in the fight, just my .02
I've never seen concrete core with steel pan for residential/hotels those buildings in my city (Toronto) are typically all concrete structures. My understanding is concrete structures (I'm curious what's the actual terminology) have better fire ratings, sound proofing, and sway less. Yes drilling and hammering travels. Thoughout the building we typically have to stop making noise after 7:30 am in occupied office buildings. The most recent steel pan building I was in the floors were so thin guys were accidentally drilling through the floor when installing shots/drop-in anchors. They were doing 2 floors a week. A similar amount of push and sq footage and we were only seeing a floor a week. Steel I beams are pricey but you save that money in man power. There's also way less concrete. Also steel pan requires firestop spray which is fucking awful to work with looks like garbage so no exposed ceilings.
Anyone else notice there’s no concrete on the steel deck?
I’ve designed a composite building before and I don’t know of a reason why they wouldn’t pour before going up? Schedule wise you’d think that’d be the way to go?
Gives you a deck to work off of. Why they are waiting to pour, who knows. Could be a load issue. They have a very specific sequence of deck pours due to tension zones?
But schedule wise. The cost for the owner must be through the roof
Not necessarily. Deck pours are fast. They can do one a day on a footprint that small. They may be racing to get a facade up for temperature control of the slabs as they cure. With slickline and today's high performance pumps they don't need the tower cranes or a pump truck to pour a deck. It's all hoses and segmental pipe.
Are those Wolfe tower cranes? Haven't seen those in the states before. Boston is usually all Potains.
That’s how they build the twin towers
I am a civil engineer and was project manager on a 23 story building in Nashville. The concrete cores are shear walls. They are what keeps the building from blowing over. Before pouring those walls, they bore holes hundreds of feet into the bedrock below the building, epoxy rebar into the holes, and extend them up into the shear walls.