Yes, this building:
http://translate.google.com/transla...ructie-bouwkunde-niet-gesmolten/17973&act=url
Those beams were purposely cut during the demolition a day or so
According to the link, the steel beams were not cut and there was no molten steel. How do you explain this?
See the molten steel where the cut was made
You are asking for proof of something that has never happened before, therefore it "can't be real".
Those beams were purposely cut during the demolition a day or so
after the fall.
Cutting at an angle like that allows the upper beam to "slide" off in a predictable manner, during demo.
This is old stuff.....and the pic has been explained several times.
Does this mean there are hundreds or thousands of unsafe tall buildings with long span supports that must be retrofitted in some way? How would you retrofit a building to prevent this problem?
While the partial or total collapse of a tall building due to fires is a rare event, NIST strongly urges building owners, operators, and designers to evaluate buildings to ensure the adequate fire performance of structural systems. Of particular concern are the effects of thermal expansion in buildings with one or more of the following characteristics: long-span floor systems, connections that cannot accommodate thermal effects, floor framing that induces asymmetric forces on girders, and composite floor systems, whose shear studs could fail due to differential thermal expansion (i.e., heat-induced expansion of material at different rates). Engineers should be able to design cost-effective fixes to address any areas of concern identified by such evaluations.
Several existing, emerging, or even anticipated capabilities could have helped prevent the collapse of WTC 7. The degree to which these capabilities improve performance remains to be evaluated. Possible options for developing cost-effective fixes include:
NIST is recommending that building standards and codes be strengthened beyond their current intent to achieve life safety to prevent structural collapse even during infrequent building fires like those in WTC 7 when sprinklers do not function, do not exist, or are overwhelmed by fire.
- More robust connections and framing systems to better resist effects of thermal expansion on the structural system.
- Structural systems expressly designed to prevent progressive collapse. Current model building codes do not require that buildings be designed to resist progressive collapse.
- Better thermal insulation (i.e., reduced conductivity and/or increased thickness) to limit heating of structural steel and minimize both thermal expansion and weakening effects. Insulation has been used to protect steel strength, but it could be used to maintain a lower temperature in the steel framing to limit thermal expansion.
- Improved compartmentation in tenant areas to limit the spread of fires.
- Thermally resistant window assemblies to limit breakage, reduce air supply and retard fire growth.
Perhaps it's not the collapse of the WTC 7 that's unique. It looks just like many other implosions so that prima facie evidence might be a good place to begin any real investigation into it. Perhaps instead it is NIST's simulation of an investigation that is unique and not the event itself or the observations surrounding it.
Because it is not the same building? A substantial portion of the building collapsed, the whole building had to be broken down after the fire. Now you are changing your request to "the whole building needs to be collapsed and it should look exactly the same as WTC7", while this is a perfect example that a steel frame building can collapse due to a "simple" fire.
Yes that is very interesting... seems we have a genuine partial collapse without the usual mitigating circumstances such as lightweight unprotected trusses etc.
Would have to remark that if 7 had collapsed in a similar manner, i.e. not straight down like a demolition...and there were not areas of extreme heat for months afterwards, the theory that it had been demolished would not be anywhere near as prevalent.
Time Report - Time Known/Reported Source
08:15 -
08:30
People recognize smell from coffee vending m
achine. Plugs are being pulled out of the
sockets on the fifth and sixth floor. The coffee machine is not touched. No visible smoke.
COT,
F, G, J
8:55
Smoke coming out of the coffee vending machine. Smoke seems to come out of a gap
between the top of the machine and the red pantry unit. The smoke is light-grey.
L
9:00
White smoke coming out of a slot above the co
ffee vending machine. A BHV-employee gets a
call about the fire and is asked to take a look at the sixth floor. A gets a message (pager)
concerning something like ‘brandcentrale’. Starting fire on the sixth floor.
COT,
A, H,
K, N, Q
9:10
Smoke coming out of the machine ‘in a stripe’ (from small slot at top front). J describes as
‘filthy black smoke’. “Fire balls
” (likely burning cups) observed coming out of machine.
COT,
H, J, Q
9:15
H and J are extinguishing a starting fire using a hand-extinguisher. Smell of an 'unpleasant'
fire stink. Big flames coming out of th
e coffee machine. F sends H and J away.
F
9:16 The FD gets call for help from a TU Delft project manager. Fire alarm push button activated. COT
9:18 The Regional Alarm Centre gets an automatic fi
re alarm from the Faculty of Architecture. COT
9:27
The first fire brigade arrives at the building and notices smoke on the outside, but no fire.
BHV-workers have evacuated the people in the building.
COT
9:32
The second fire officer reports a ‘middelbrand’ (m
edium fire). The first fire officer sends four
people with ‘flatkratjes’ to the sixth floor. The people on the sixth floor are trying to
extinguish the fire by using the fire hose,
there’s almost no pressure, so it’s useless.
COT
9:33
The second fire officer reports a ‘grote brand’ (l
arge fire). The heat is intense and a thick layer
of smoke fills the space. Soon flames are starti
ng on the ceiling and they
retreat. Just before
they want to leave through the door, there is
a flashover which puts the whole area on fire.
COT
9:50 Conflagration on 6 & 7 South, both sides (E & W) and extending very quickly via the façade. COT
11:30 Floors 6-11 on fire (South section) COT
12:15 All fire fighters now outside of the build
ing. Fire spread into Center section. COT
12:55 Fire spreads to North section (10
th
floor) Photos
13:39 Fire observed on North section, Floors 7-11 Photos
16:40 Part of North section collapses COT
http://www.skeptic.com/eskeptic/11-09-07/#featureWHAT CAUSED BUILDING 7 TO COLLAPSE? Many firefighters reported seeing structural deformations of Building 7 hours before its collapse, including the top FDNY fire Chief Daniel Nigro, who stated, “I feared a collapse of Building 7 (as did many on my staff). The collapse of WTC 1 damaged portions of the lower floors of 7. Building 7 was built on a small number of large columns providing an open Atrium on the lower levels. Fires on many floors of WTC 7 burned without sufficient water supply to attack them.
WHAT CAUSED BUILDING 7 TO COLLAPSE? Many firefighters reported seeing structural deformations of Building 7 hours before its collapse, including the top FDNY fire Chief Daniel Nigro, who stated, “I feared a collapse of Building 7 (as did many on my staff). The collapse of WTC 1 damaged portions of the lower floors of 7. Building 7 was built on a small number of large columns providing an open Atrium on the lower levels. Fires on many floors of WTC 7 burned without sufficient water supply to attack them.
he building was constructed above a Con Edison substation that had been on the site since 1967.[6] The substation had a caisson foundation designed to carry the weight of a future building of 25 stories containing 600,000 sq ft (56,000 m2).[7] The final design for 7 World Trade Center was for a much larger building than originally planned when the substation was built.[8] The structural design of 7 World Trade Center therefore included a system of gravity column transfer trusses and girders, located between floors 5 and 7, to transfer loads to the smaller foundation.[9] Existing caissons installed in 1967 were used, along with new ones, to accommodate the building. The 5th floor functioned as a structural diaphragm, providing lateral stability and distribution of loads between the new and old caissons. Above the 7th floor, the building's structure was a typical tube-frame design, with columns in the core and on the perimeter, and lateral loads resisted by perimeter moment frames.[7]
Transfer trusses used on the 5–7th floors to redistribute load to the foundation
A shipping and receiving ramp, which served the entire World Trade Center complex, occupied the eastern quarter of the 7 World Trade Center footprint. The building was open below the 3rd floor, providing space for truck clearance on the shipping ramp.[7] The spray-on fireproofing for structural steel elements was gypsum-based Monokote which had a two-hour fire rating for steel beams, girders and trusses, and a three-hour rating for columns.
