The paragraph that follows the one you posted is more to the point at hand.
Could the fires in WTC 7 heat the 4 ton per floor columns to the point of failure?
The evidence suggests not.
What evidence says there weren't fires?
"The most important operational decision to be made that afternoon was the collapse (Of the WTC towers) had damaged 7 World Trade Center, which is about a 50 story building, at Vesey between West Broadway and Washington Street.
It had very heavy fire on many floors and I ordered the evacuation of an area sufficient around to protect our members, so we had to give up some rescue operations that were going on at the time and back the people away far enough so that if 7 World Trade did collapse, we [wouldn't] lose any more people. We continued to operate on what we could from that distance and approximately an hour and a half after that order was [given], at 5:30 in the afternoon, World Trade Center collapsed completely" - Daniel Nigro, Chief of Department
"Early on, there was concern that 7 World Trade Center might have been both impacted by the collapsing tower and had
several fires in it and there was a concern that it might collapse. So we instructed that a collapse area -- (Q. A collapse zone?) -- Yeah -- be set up and maintained so that when the expected collapse of 7 happened, we wouldn't have people working in it. There was considerable discussion with Con Ed regarding the substation in that building and the feeders and the oil coolants and so on. And their concern was of the type of fire we might have when it collapsed." - Chief Cruthers
"A little north of Vesey I said, we’ll go down, let’s see what’s going on. A couple of the other officers and I were going to see what was going on. We were told to go to Greenwich and Vesey and see what’s going on. So we go there and on the north and east side of 7 it didn’t look like there was any damage at all, but then you looked on the south side of 7 there had to be a hole 20 stories tall in the building,
with fire on several floors. Debris was falling down on the building and it didn’t look good." - Captain Chris Boyle
"No, not right away, and that’s probably why it stood for so long because it took a while for that fire to develop.
It was a heavy body of fire in there and then we didn’t make any attempt to fight it. That was just one of those wars we were just going to lose. We were concerned about the collapse of a 47-story building there. We were worried about additional collapse there of what was remaining standing of the towers and the Marriott, so we started pulling the people back after a couple of hours of surface removal and searches along the surface of the debris. We started to pull guys back because we were concerned for their safety." - Deputy Chief Peter Hayden
Or are they lying?
What if the fires were just smoldering?
"Smoldering is a relatively slow combustion process that occurs between oxygen in the air and a solid fuel. No flame is present, however the presence of very hot materials is on the surface of which combustion is proceeding. The surface undergoes glowing and charring.
The glowing is indicative of a temperature in excess of 1000°C (1832°F). A smoldering or glowing condition can occur at any point in the fire with the controlling factor being ventilation." - NFPA 921: Guide for Fire and Explosion Investigations 3rd Edition
Now what would if they were diffusion flames?
A Diffusion Flame is defined as a combustion process in which the fuel gas and oxygen are transported into the reaction zone due to concentration differences.
The vast majority of un-wanted and un-controlled fires are diffusion flames.
During a flaming fire, conditions may exist that decrease the oxygen level below 16%. This causes the combustion process to slow, the flames subside and the temperature begins to decrease.
With no set temperature as it would differ on the material burning...
Approximate Power Usage/Peak Heat Release Rate
Burning cigarette: 5W
Standard “A” Light Bulbs: 15 to 200 W
Burning match: 80 W
Coffee maker, hair dryer, toaster: 500 to 1500 W or 0.5 to 1.5 kW
Burning Coffee Maker: 40 kW
Small Trash Can, Trash Bag Fires: 50 to 300 kW
Burning Upholstered Chair: 80 kW to 2.5 MW
Burning Upholstered Sofa: 3,000 kW or 3 MW
Burning Christmas Tree: 1.6 MW to 5.2 MW
Base Design Fire: 5.3 MW
Even with a two hour rating on the fire insulation, that building held up substantially. It also accounts for the fire growth in the building as witnessed by firefighters. If the fires evolved from smoldering to diffusion flames, there would a higher heat release. Most temperatures referenced are based on STP
Standard Temperature and Pressure (STP) is a standard set of conditions for experimental measurements, to enable comparisons to be made between sets of data. Internationally, the current STP defined by the IUPAC (International Union of Pure and Applied Chemistry) is an absolute pressure of 100.00 kPa (1 bar) and a temperature of 273.15 K
So it is clear that any combustible can exceed the STP findings.
Columns and certain other structural elements are normally exposed to fire from all sides. In this fire, the steel columns retained their structural integrity and held their loads. Experience in this and similar high-rise fires suggest that columns are the least vulnerable structural members, due to their mass and relatively short height between restraints (floor to floor). Major damage has occurred to horizontal members, without compromising the vertical supports. [/COLOR]
Standard Girder and Beam construction is very different from the tube construction that the WTC 7 was designed on.
The Empire State Building is the best example of a Girder and Beam construction.
The space between the columns and the Girders are shorter as compared to the tube frame, where it very open between the exterior walls to the core.
Now what does the NFPA say about Open Truss and Solid Girder Construction?
According to NFPA 921:
Fire fighters may be injured and killed when fire-damaged roof and floor truss systems collapse, sometimes without warning.
Understand that fire ratings may not be truly representative of real-time fire conditions and that truss systems' performance may be affected by fire severity.
More than 60% of the roof systems in the United States are built using a truss system. By design, wooden truss systems contain a significant fuel load and are often hidden from sight. Fires in truss systems can burn for long periods before detection and can spread quickly across or through the trusses.
Steel trusses are also prone to failure under fire conditions and may fail in less time than a wooden truss under the same conditions.
The number of fire fighter fatalities related to structural collapse could be significantly reduced through proper education and information concerning truss construction. Fire fighters should be discouraged from risking their lives solely for property protection activities.
Unfortunately, fires are not predictable: conditions often deteriorate quickly, and fire-damaged building components, including trusses, can collapse with little warning. Engineering calculations provide data for an approximate time of failure under specified fire conditions; however, under uncontrolled fire conditions, the time to truss failure is unpredictable.
All-steel trusses present their own hazards when exposed to fire. The mass and surface area of steel truss components are factors that determine time to failure. A heavy, thick section of steel has greater resistance to fire than a lightweight section of the same length because of the increased mass. A large, solid steel truss can absorb heat and take longer to reach its failure temperature, whereas a lightweight steel truss such as an open-web bar joist will be heated to its failure temperature much faster.
Once the failure temperature is reached, heavy steel trusses and lightweight metal trusses will react to the fire and fail in a similar manner. A steel member fails at the internal temperature of the steel and not at the ambient air temperature. This temperature is often referred to as the critical temperature of the steel member.
Findings reported by the National Engineered Lightweight Construction Fire Research Project indicate that unprotected lightweight steel C-joists fail within 4 to 6 minutes of exposure to fire [Grundahl 1992]. Testing conducted by the U.S. Bureau of Standards (now known as the National Institute of Standards and Technology, or NIST) showed that unprotected steel open-web bar joists reached 1,200º F in 6 to 8 minutes [Brannigan 1999]. Table D-1 illustrates that steel retains only 25% of its original strength at 1,200º F and retains only half its original strength at approximately 900 ºF. Building design calculations are based on original strength at normal temperatures. At elevated temperatures, steel may retain no excess strength.
Steel is noncombustible and does not contribute fuel to a fire. This property may cause a false sense of security and overshadow the fact that steel loses strength when exposed to temperatures commonly found in structural fires. Steel has a high thermal conductivity, which means it can transfer heat away from a localized source and act as a heat sink. As long as the flame impingement is localized, the steel can transfer heat to other regions of the member-and thus the time to reach the critical temperature is delayed. If an intense fire is evenly distributed along the steel member, the critical temperature may be reached very quickly. Steel also has a high coefficient of expansion that results in the expansion of steel members as they are heated. As an example, a 50-foot-long steel beam heated uniformly over its length from 72° to 972° F will expand in length by 3.9 inches. The same beam uniformly heated to 800° F would expand by 3.2 inches; if heated to 1,200° F, the beam would expand by 4.9 inches [Grundahl 1991; Cotes 1997].
Source
Table D1:
Code:
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Internal of | % of original strength | % yield strength
the steel (F) | retained by the steel | lost by steel
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70 | 100 | 0
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400 | 87.5 | 12.5
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600 | 72.5 | 27.5
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800 | 57.5 | 42.5
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1,000 | 42.5 | 57.5
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1,200 | 25 | 75
Source Tapley (1990).
