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Originally posted by billybob
yeah.
well, here's the thing.
say you have two bowling balls,
Originally posted by phiniks
Originally posted by billybob
yeah.
well, here's the thing.
say you have two bowling balls,
Say, you drop a bowling ball from a 100 story height.. when it passes a bowling ball on the 50th floor, it knocks that one and it starts to fall too..
now, from that moment on.. which is what the video shows (the first ball being the building above the filmed area coming down) which goes faster: the 1st ball, or the second.. after 1 second, ball 2 has a speed of 9,81 meters/second, ball 1 is allready falling for, say 5 seconds, and has a speed of about 49 meters per second.
[edit on 31-3-2006 by phiniks]
Originally posted by yadboy
Originally posted by HowardRoark
Then you are probably familiar with supply and return air systems, air shafts, and air fresh air intakes.
What would happen to the air in an air shaft as the floor is feeds collapses?
Not sure what your trying to allude to, but more likely than not the air in the ductwork would simply be forced back out the supply diffusers and return air grilles. Some would be trapped momentarily by the fire dampers, but that wouldn't last. Commercial HVAC is usually sheet metal for the most part, not really that sturdy, if anything it probably wouldn't have made much difference one way or the other.
Originally posted by yadboy
There WOULD be more resistance to the collapse from the structural steel in that building.
Originally posted by HowardRoark
Can you do the calculations, or are you just a CAD operator?
Originally posted by yadboy
Yeah, see there this thing called "standards", it's a bunch of rule books dreamed up by guys in a lab that are trying to simulate real world conditions to make things work better or safer. Fire protection standards are WAY overdone. But you gotta follow their rules or you don't pass inspection. Overreaching standards add quite a bit to the cost of many construction projects, but you gotta do what the man says.
Originally posted by Springer
I am pretty sure WCIP was referring to the revised version of Newton member phlinks has created above.
WooooT!
Springer...
[edit on 3-31-2006 by Springer]
Originally posted by HowardRoark
Then you are probably familiar with supply and return air systems, air shafts, and air fresh air intakes.
What would happen to the air in an air shaft as the floor is feeds collapses?
Originally posted by yadboy
Not sure what your trying to allude to, but more likely than not the air in the ductwork would simply be forced back out the supply diffusers and return air grilles. Some would be trapped momentarily by the fire dampers, but that wouldn't last. Commercial HVAC is usually sheet metal for the most part, not really that sturdy, if anything it probably wouldn't have made much difference one way or the other.
Originally posted by HowardRoark
No, I am talking about the type of air handling system typically found in a large high rise. You have two air shafts in the core. A supply and a return shaft. These shafts, or plenums) are usually not ducted, the drywall enclosure is the duct. At each floor the supply ductwork branches out from the supply shaft to the floors. The return is through the open ceiling plenum and is not ducted.
The ducts lead down to the fan room on the mechanical floor where a certain percentage of the return air is remixed with the fresh air intake and sent back to the floors.
If the collapse forces the air out between tow floors, then the air will have to go somewhere. If will travel down the duct and out the fan room intakes (in a giant squib like puff).
Originally posted by yadboy
There WOULD be more resistance to the collapse from the structural steel in that building.
Originally posted by HowardRoark
Really, WAY overdone? I have NEVER heard a structural engineer state that.
Have you read this yet?
fire-research.group.shef.ac.uk...
Griff wrote:
WCIP...what's not worth it? I was only pointing out that Howard was right in his equation.
HowardRoark wrote:
Force equals momentum divided by time.
Originally posted by wecomeinpeace
But anyway while I'm here, force is not equal to momentum over time, it is equal to the change in momentum over the change in time. A force acting on an object causes a change in its momentum. The shorter the time it takes to create the same change in momentum, the larger the force. Or put another way, changing a large momentum in a very short time takes a very large force.
Acceleration is the change in velocity over the change in time. So (where mass is constant), F = ma = m*dv/dt = dp/dt
Originally posted by wecomeinpeace
But anyway while I'm here, force is not equal to momentum over time, it is equal to the change in momentum over the change in time.
Originally posted by HowardRoark
If we assume that the impact caused the planes momentum to go from 400 mph to 0 mph in ½ a second (totally arbitrary numbers), then we can calculate the force involved.
Originally posted by yadboy
we mostly do gov. facilities & comercial manufacturing facilities here
Originally posted by yadboy
Yes actually I hear that on a weekly basis from structural engineers, mechanical engineers & civil engineers. It is better to be safe than sorry, so of course we follow all standards, but those standards are written to give a lot more protection than is needed in the real world in many cases.
Originally posted by HowardRoark
Well if you want to get picky about it, time doesn’t “change,” it just is a straight value. 1, sec, 3 sec, ect.) The delta is implied.
Originally posted by HowardRoark
...the impact caused the planes momentum to go from 400 mph to 0 mph
Originally posted by HowardRoark
If we assume that the impact... then we can calculate the force involved.
Originally posted by yadboy
Your pdf is apples to the WTC oranges. Floor trusses are not meant to support buildings. They are just there to keep the floor in place. Comparing a floor truss to a structural beam is like comparing a chopstick to a steel pipe.
Originally posted by HowardRoark
You seem to be rather antagonistic latley, so . . .
Originally posted by phiniks
If you guys judge my knowledge about the simplest mechanics by simply not being able to read then sorry, but go do something else.. my words are bent even before you start you replies.. buncha disinformation agents. burn in hell.
Originally posted by pavil
What if one floor of the WTC below the pancaking gave way early due to being unable to sustain the stress more than the rest of the floors? Wouldn't that mess with all the calculations being tossed around here.