Anyone feel like explaining how tension cables work in post-tensioned concrete? And what exactly is post-tensioned concrete?
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Post-tensioned concrete is done on-site when casting floor slabs- what they do is lay steel cables across the area to be filled, in a material that allows them to not bond with the concrete and concrete is then poured in over top of the cables. As the concrete dries, the cables are tightened giving the slab compressional strength - the steel cables embedded in the concrete then provide the slab with tensional strength, something which is lost in the initial process of stressing the concrete. The benefits are that you optimize the component to get thinner and stronger more versatile concrete elements for the project you are building.
p5
 
p5connex said:
Post-tensioned concrete is done on-site when casting floor slabs- what they do is lay steel cables across the area to be filled, in a material that allows them to not bond with the concrete and concrete is then poured in over top of the cables. As the concrete dries, the cables are tightened giving the slab compressional strength - the steel cables embedded in the concrete then provide the slab with tensional strength, something which is lost in the initial process of stressing the concrete. The benefits are that you optimize the component to get thinner and stronger more versatile concrete elements for the project you are building.
p5
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Thank you for the reply.
 
p5connex said:
Post-tensioned concrete is done on-site when casting floor slabs- what they do is lay steel cables across the area to be filled, in a material that allows them to not bond with the concrete and concrete is then poured in over top of the cables. As the concrete dries, the cables are tightened giving the slab compressional strength - the steel cables embedded in the concrete then provide the slab with tensional strength, something which is lost in the initial process of stressing the concrete. The benefits are that you optimize the component to get thinner and stronger more versatile concrete elements for the project you are building.
p5
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Concrete industry insider?
 
The concrete deck for the 2nd floor and ramp to the third floor was all poured two nights ago. Third floor forming is now being installed and is almost complete on the west and north sides. Logically, they appear to be working in a clockwise fashion in constructuing the forming and then pouring the concrete, working their way up and around following the natural flow. Given recent progress, it looks like this tower will now start to rise a lot faster. Forming work is all being done from scratch by hand - no "flying forms" yet for this one. The most work involved appears to be in laying out all the conduit and post-tensioning cables/rebar.

The somewhat dated marketing materials on the TT website state that this building will connect to the PATH network. Does anyone know if this is true and, if so, precisely where it will connect? Scotia Plaza would seem the logical place for this, next to the National Club entrance in the concourse. I need to know how to get quick access to that new martini bar on the corner of Bay and Adelaide . . .
 
41, I would think that is where PATH will connect, next to the National Club entrance.

Have you ever used that entrance to the NC?
 
At this page here (scroll down), from a seriously out of date article in the Star, shows the planned connection to Trump. I know it was planned, but I haven't heard anything about it in ages.
 
I'm sure the PATH connection is canceled. Why bother building a connection to a seven-story parking garage? :D
 
I can't remember where I got this from but it's a .pdf named "PATH_2008_CityofToronto". Whether it's correct or not can be debated. Below is a screenshot showing a connection to Trump.

path.jpg
 
I hope it's still on the radar, I mean it is an important connection.
 
p5connex said:
Post-tensioned concrete is done on-site when casting floor slabs- what they do is lay steel cables across the area to be filled, in a material that allows them to not bond with the concrete and concrete is then poured in over top of the cables. As the concrete dries, the cables are tightened giving the slab compressional strength - the steel cables embedded in the concrete then provide the slab with tensional strength, something which is lost in the initial process of stressing the concrete. The benefits are that you optimize the component to get thinner and stronger more versatile concrete elements for the project you are building.
p5
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Your definition of post tensioning is correct, however your explanation as to why it improves the concrete's strength is wrong. The problem lies with this sentence:

"the steel cables embedded in the concrete then provide the slab with tensional strength, something which is lost in the initial process of stressing the concrete."

The cables themselves do not increase the slab's resistance to tension, as tensional forces are carried by the rebar which is present in the concrete regardless. The key point is that the cables induce a uniform compressive force in the concrete before it is even loaded, which means that a greater live load is required to bring the underside of the slab back into tension. In other words, pre or post tensioning does nothing to increase the concrete's actual resistance to tension, it simply increases the live load required to put the concrete into tension in the first place. Since concrete has almost no ability to resist tension, this is a major point!

The other way of looking at it is that for any given live load - ie the live load specified in the building code for residential occupancy - a thinner slab is able to resist the load if it is post tensioned.
 
Concrete industry insider?
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No, but I had wanted to use this process in a building, which lead me to doing some research on the subject. This type of construction is fairly common in high-rise residential buildings, but also in areas when pouring slabs on grade, where soil conditions are continually changing, which lead to the concrete cracking and buckling..Not good.

Your definition of post tensioning is correct, however your explanation as to why it improves the concrete's strength is wrong.
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Thanks for clarifying that Chuck. I wasn't sure if my explanation was 100%, but felt it was somewhere along those lines.
 
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Actually, I can't think of many other recent example of it in Toronto. Around here it still remains somewhat uncommon, tho it makes sense in a tower like Trump since it also allows you to go much greater distances without columns. If I'm not mistaken Trump has no interior columns at all, just the exterior ones and then the core in the middle of the floorplate
 
March 26

Trump is starting to rise faster. They are now working on the third level and the National Club will no longer get billboard revenue because Trump is blocking the view.
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The parking floor is slightly sloped.
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Adelaide side looking east.
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Adelaide side looking west.
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From Adelaide near Yonge looking west.
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