egotrippin said:
.. but I think you get the point.
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I sure did.

I still have another questions. They must be driving posts -- for lack of better word -- in the ground to 'anchor' the structure to prevent it from tilting in case of a high wind or minor earthquake? Or the structure is heavy enough to not to tilt in case of high winds. In Toronto we have had strong winds -- storms -- once in a while.
 
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steveve said:
Excavation/Foundations have always amazed me... its quite amazing how a building (some 75 stories) can rest only 5 or 6 levels below ground. yet be able to support such a huge tower!. I know the bedrock is very strong but doesn't the ground below sorta "shake" during an earthquake or the foundations crack?. and i know in extremely active places, a weak buildings' foundations can completely dismembered during powerful earthquakes....
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I was staring into the pit earlier this evening myself thinking this exact same thing.

Back-of-napkin calculation: Aura is about 75 storeys, each floor could be represented by a poured slab ~18 inches thick (floor + walls). That 75 storey building weighs as much as a 110-ish foot tall block of solid concrete. But of course, they've excavated out 60+feet of compacted, water-saturated till, and a bit of limestone. You're less than doubling the weight on the bedrock from the existing overburden.

The building adds about 40psi to the bedrock over what was there before. Sounds like a lot, but you put more pressure on the ground when you push off with your foot while walking.

Of course, very rough numbers, but brings it into perspective. Obviously the weight isn't uniformly distributed, but it's not nearly what you'd imagine.

As for the structure itself, well, reinforced concrete is very, very strong under compression.
 
I believe most highrises in downtown Toronto use rock anchors, where they drill into the rock and grout around the bolts with concrete to anchor the building foundations to the bedrock. This would stop any overturning due to earthquake and wind loads. Anyone know what level of earthquake we design our highrises to here in TO?
 
Thanks for the information,civdis.

Any idea as to how deep one has to go to reach bedrock?
 
HHC said:
It does to an extent, Mr. Physicist.
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How do you figure? The building is sitting on the piles, not on the shoring. You can build a tower with no basement at all if you really wanted. All you'd need is longer piles and a small excavation for the footing. The only reason the walls of the excavation need to be reinforced is to prevent them from buckling during the construction of the parking garage. Hell, look at Uptown/CrystalBlu. There was no wall separating the two excavations, but both towers went up just fine having just three walls around their pits.
 
It is true that the depth to rock varies around the city, but generally, it is shallower as you move towards the lake. Pretty much all of the major towers south of Dundas Street sit on shale while most of the towers up at Bloor do not. A little known fact is that if you were to keep digging for another 300m or so (one First Canadian Place), you would hit was is called basement rock, otherwise known as the Canadian Shield (think Muskoka Granite).
 
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aura1010.jpg
 
buildup said:
Talking about wind shear? I assume you guys heard the story about the CitiCorp building in NY?
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No. I haven't. Tell me, please. I will be living on a high floor in AURA. What it is that I should worry about.
 
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sodapop said:
i wouldnt want to be living in rocp when they start driving those massive pilings into the ground thanks for the update androiduk
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It shouldn't be that bad. I lived in RoCP1( and I still do) when RoCP2 was being constructed and, lately, Luminiere.
 
I can't remember the whole story but I believe they found a problem in the stuctural system after the building was completed (something to do with joint welds or bolts). It was determined that in extreme wind conditions, the building could be unstable due to these joints. The entire building was retrofitted under a shroud of secrecy in order not to panic people. Apparently, they dodged a major bullet because a hurricane almost hit NYC while the retrofit was underway.
 
By the way KA1, if Aura is typical of many condo projects, they will be using a reinforced concrete shear wall system that does not rely on bolted or welded joints like a steel structure does. I wouldn't be concerned because structural engineers use very large safety factors in the design of these buildings.
 
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