Hier meine Analyse zum Thomas Eager Beitrag:
In order to make each tower capable of withstanding this wind load, the architects selected a lightweight “perimeter tube” design consisting of 244 exterior columns of 36 cm square steel box section on 100 cm centers (see Figure 3). This permitted windows more than one-half meter wide. Inside this outer tube there was a 27 m × 40 m core, which was designed to support the weight of the tower. It also housed the elevators, the stairwells, and the mechanical risers and utilities. Web joists 80 cm tall connected the core to the perimeter at each story. Concrete slabs were poured over these joists to form the floors.
The early news reports noted how well the towers withstood the initial impact of the aircraft; however, when one recognizes that the buildings had more than 1,000 times the mass of the aircraft and had been designed to resist steady wind loads of 30 times the weight of the aircraft, this ability to withstand the initial impact is hardly surprising. Furthermore, since there was no significant wind on September 11, the outer perimeter columns were only stressed before the impact to around 1/3 of their 200 MPa design allowable.
The only individual metal component of the aircraft that is comparable in strength to the box perimeter columns of the WTC is the keel beam at the bottom of the aircraft fuselage. While the aircraft impact undoubtedly destroyed several columns in the WTC perimeter wall, the number of columns lost on the initial impact was not large and the loads were shifted to remaining columns in this highly redundant structure. Of equal or even greater significance during this initial impact was the explosion when 90,000 L gallons of jet fuel, comprising nearly 1/3 of the aircraft’s weight, ignited. The ensuing fire was clearly the principal cause of the collapse.
Anmerkung : die 90 000 Liter sind natürlich falsch!
In a diffuse flame, the fuel and the oxidant are not mixed before ignition, but flow together in an uncontrolled manner and combust when the fuel/oxidant ratios reach values within the flammable range. A fireplace flame is a diffuse flame burning in air, as was the WTC fire.
Diffuse flames generate the lowest heat intensities of the three flame types.
Anmerkung: sollten endllich ALLE hier mal kapieren!
This is why the temperatures in a residential fire are usually in the 500°C to 650°C range.2,3 It is known that the WTC fire was a fuel-rich, diffuse flame as evidenced by the copious black smoke. Soot is generated by incompletely burned fuel; hence, the WTC fire was fuel rich—hardly surprising with 90,000 L of jet fuel available. Factors such as flame volume and quantity of soot decrease the radiative heat loss in the fire, moving the temperature closer to the maximum of 1,000°C. However, it is highly unlikely that the steel at the WTC experienced temperatures above the 750–800°C range. All reports that the steel melted at 1,500°C are using imprecise terminology at best.
Anmerkung: der Stahl erreichte maximal 300 Grad im Impakt Bereich und Eager gibt zu, dass : selbst bei 650 Grad C. ( 50 % Verminderung der Tragkraft) noch nichts passiert wäre.
hier:
It is known that structural steel begins to soften around 425°C and loses about half of its strength at 650°C.4 This is why steel is stress relieved in this temperature range. But even a 50% loss of strength is still insufficient, by itself, to explain the WTC collapse. It was noted above that the wind load controlled the design allowables. The WTC, on this low-wind day, was likely not stressed more than a third of the design allowable, which is roughly one-fifth of the yield strength of the steel. Even with its strength halved, the steel could still support two to three times the stresses imposed by a 650°C fire.
und hier zerstiebt die Aluminium Diskussion:
Some reports suggest that the aluminum from the aircraft ignited, creating very high temperatures. While it is possible to ignite aluminum under special conditions, such conditions are not commonly attained in a hydrocarbon-based diffuse flame. In addition, the flame would be white hot, like a giant sparkler. There was no evidence of such aluminum ignition, which would have been visible even through the dense soot.
hier wird es semantisch:
"As the joists on one or two of the most heavily burned floors gave way and the outer box columns began to bow outward, the floors above them also fell. The floor below (with its 1,300 t design capacity) could not support the roughly 45,000 t of ten floors (or more) above crashing down on these angle clips. This started the domino effect that caused the buildings to collapse within ten seconds, hitting bottom with an estimated speed of 200 km per hour. If it had been free fall, with no restraint, the collapse would have only taken eight seconds and would have impacted at 300 km/h.1 It has been suggested that it was fortunate that the WTC did not tip over onto other buildings surrounding the area. There are several points that should be made. First, the building is not solid; it is 95 percent air and, hence, can implode onto itself. Second, there is no lateral load, even the impact of a speeding aircraft, which is sufficient to move the center of gravity one hundred feet to the side such that it is not within the base footprint of the structure. Third, given the near free-fall collapse, there was insufficient time for portions to attain significant lateral velocity. To summarize all of these points, a 500,000 t structure has too much inertia to fall in any direction other than nearly straight down. "
Anmerkung: die 45 000 Tonnen von oben waren keinesfalls inert, wie eager meint, sondern hätten zur Seite (der beschädigten Seite, Ecke) fallen müssen, weil das Momentum der Bewegung (die durch den einseitigen Fall erlangte kinetische Energie die sich auf der beschädigten Seite verstärkte (Kraftvektor)), nicht allein nach unten erfolgte.
Die Feuer (selbst bis 500 GRad C im inner core, was nach einer oder 1,5 Std. difffuser Feuer nicht möglich ist) reichten nicht aus um inner core und outer perimeter wall entscheidend zu schwächen.
Und selbst wenn, dann hätten der gesamte inner core unterhalb und Riesenteile der outer perimeter wall stehen bleiben bzw. (perimeter wall) kippen müssen.
Der dritte Punkt von Eager ist übrigens der Lächerlichste, ein klassischer Zirkelschluss.
No designer of the WTC anticipated, nor should have anticipated, a 90,000 L Molotov cocktail on one of the building floors.
Auch hier wieder: 90 000 l (nicht ein Drittel davon war tatsächlich der Fall) und natürlich waren die Türme auf 90 000 l Kerosin hin konstruiert, alos das was eine
Boing 707 maximal an Tankinhalt hat.Oder glaub Mr.Eager, man berechnet eine 707 mit leeren Tank als "Last"?
Auch seine Bezeichnung Molotow Cockteail ist verräterisch für die falsche Denke, Feuer hätte nach 56 Minuten resp. 102 Minuten, strukturell irgend was schwächen können in den Türmen.
| 3.915 Beiträge
zitieren
| 23.327 Beiträge
Besucher
Forum Statistiken
