What was the weight of a WTC Tower?

If you really want to get into the physics of the collapse of the WTC Twin Towers, sooner or later you will need to know the weight (or mass) of a WTC Tower, or at least a Tower block of 15 to 30 floors. After all, the potential energy of a structure ( = Mgh) and the kinetic energy of a falling block ( = 1/2 Mv^2) are both functions of mass…......See, for example, the calculations presented at :

http://www.911myths.com/html/other_contributions.html

If you search for published values of the mass of WTC 1 or 2, the number quoted is invariably close to 500,000,000 kg or 500,000 tonnes. But where does this number come from?

I have certainly never seen a detailed calculation of the mass of WTC 1 or 2; but there are plenty of references on the web for the weight of the materials used in the construction of the WTC Towers. For example, the weight of structural steel used in each Tower is generally reported to be 96,000,000 kg and the weight of concrete is said to be 48,000,000 kg per Tower. I have also seen the weight of aluminum cladding reported to be 2,000,000 kg, and the weight of wallboard quoted at 8,000,000 kg per Tower, giving a total weight of structural materials of 154,000,000 kg per Tower.

Now let’s add in reasonable “guesstimates” for plumbing fixtures (5,000,000, kg), air conditioning (5,000,000 kg), electrical and telecommunication wiring (5,000,000 kg) and we have an additional 15,000,000 kg of structural mass that civil engineers always include as part of the “dead load” of a building. Thus combining all these contributions, we arrive at a weight, or dead load, of 169,000,000 kg for one WTC Tower. Surprisingly this accounts for only about 1/3rd of the oft-quoted 500,000,000 kg, so where is the missing mass?

The answer would appear to be in what civil engineers call the “live load” of the building, which in the case of one WTC Tower would have to be (500,000,000 - 169,000,000) kg or 331,000,000 kg, i.e., twice the dead load! We will show that this result leads to major problems …..

But first, let’s convert our load data in to more familiar engineering units based on floor areas. Building codes usually express loads in pounds per square foot (psf) or kilograms per square meter (kg/m^2). For example, the specification for a high live-load capacity floor is typically about 150 psf or 750 kg/m^2.

From the dimensions of a WTC Tower we estimate the available floor area per Tower was about 320,000 square meters. Hence, the live load was 331,000,000 kg divided by 320,000 m^2 which is equal to 1034 kg/m^2 or 212 psf. We see from the live load example given in the previous paragraph that 212 psf represents a very high live loading. But let’s look at just how high this load is…..

If the live loading within one WTC Tower really was 331,000,000 kg (more or less), that equals 3,009,091 kg per floor or about 3000 tonnes per floor!! I believe each WTC Tower employed about 15,000 people so we have an average of 136 people per floor. This means that each person working in the Twin Towers contributed about 22 tonnes of live load!!! That's an awful lot of office furniture, computers, printers, telephones..... or am I missing something?

NEU-FONZE