JК
11 сентября 2001 :: Мейссан Тьерри
Страница: 245 из 286Since there were (at most) 120 gusset plates and seat angles, these add in 120 x 149 = 17880 cubic inches. The 76 horizontal diagonal brace plates add in another 76 x 90 x 3/2 x 1/2 = 5130 cubic inches for an addition of (17880 + 5130)/1728 = 13.3 cubic feet of steel to our total.
The upper chord (top section) of one of the double trusses consisted of four pieces of 1/8 inch thick angle iron, as illustrated below (it is circled in red).
Below, is a more detailed view of the cross section of the top chord of a transverse truss (left) and double truss (right).
So, the upper chord has a cross sectional area of
((2 + 1.25) + (1.25 + 2))/8 = 0.8125 square inches for a transverse truss and,
((2 + 1.25) + (1.25 + 7 + 1.25) + (1.25 + 2))/8 = 2 square inches for a double truss.
Since we have no information concerning the lower chord (and the «official» pictures are inconsistent and nowhere near to scale) we will assume it has the same dimensions as the upper chord.
Now summing the volume of steel in the top and bottom chords and diagonal rods, we have the following per foot volumes:
2 x 0.8125 x 12 + 20.16 = 39.7 cubic inches per foot for the transverse trusses, and
2 x 2 x 12 + 2 x 20.16 = 88.3 cubic inches per foot for the double trusses.
Now we need to calculate the total length of double and transverse trussing. There were apparently, 60 double trusses spanning the 60 feet from the perimeter wall to (a beam attached to) the core and 24 double trusses spanning the 35 feet from the perimeter wall to the core. They are pictured in the following graphic:
The overall length of double trussing was thus 60 x 60 + 24 x 35 = 4440 feet. Transverse trusses ran perpendicular to the double trusses as illustrated:
The overall length of transverse trussing was thus 8 x 207 + 4 x 87 = 2004 feet.
There was also a lesser supporting feature called «intermediate support angle». Since all we know about the intermediate support angle, is that its support capabilities were inferior to the double and transverse trusses, we shall be generous and assume that it was similar in nature to the transverse trusses. This adds another 1764 feet, to give a total of 2004 + 1764 = 3768 feet of transverse trussing.
Hence, the volume of steel in the double trusses was 4440 x 88.3/1728 = 227 cubic feet.
And the volume of steel in the transverse trusses was 3768 x 39.7/1728 = 86.6 cubic feet.
So the overall per floor volume of steel in the floor support system was
150 + 13.3 + 227 + 86.6 = 477 cubic feet.
The upper chord (top section) of one of the double trusses consisted of four pieces of 1/8 inch thick angle iron, as illustrated below (it is circled in red).
Below, is a more detailed view of the cross section of the top chord of a transverse truss (left) and double truss (right).
So, the upper chord has a cross sectional area of
((2 + 1.25) + (1.25 + 2))/8 = 0.8125 square inches for a transverse truss and,
((2 + 1.25) + (1.25 + 7 + 1.25) + (1.25 + 2))/8 = 2 square inches for a double truss.
Since we have no information concerning the lower chord (and the «official» pictures are inconsistent and nowhere near to scale) we will assume it has the same dimensions as the upper chord.
Now summing the volume of steel in the top and bottom chords and diagonal rods, we have the following per foot volumes:
2 x 0.8125 x 12 + 20.16 = 39.7 cubic inches per foot for the transverse trusses, and
2 x 2 x 12 + 2 x 20.16 = 88.3 cubic inches per foot for the double trusses.
Now we need to calculate the total length of double and transverse trussing. There were apparently, 60 double trusses spanning the 60 feet from the perimeter wall to (a beam attached to) the core and 24 double trusses spanning the 35 feet from the perimeter wall to the core. They are pictured in the following graphic:
The overall length of double trussing was thus 60 x 60 + 24 x 35 = 4440 feet. Transverse trusses ran perpendicular to the double trusses as illustrated:
The overall length of transverse trussing was thus 8 x 207 + 4 x 87 = 2004 feet.
There was also a lesser supporting feature called «intermediate support angle». Since all we know about the intermediate support angle, is that its support capabilities were inferior to the double and transverse trusses, we shall be generous and assume that it was similar in nature to the transverse trusses. This adds another 1764 feet, to give a total of 2004 + 1764 = 3768 feet of transverse trussing.
Hence, the volume of steel in the double trusses was 4440 x 88.3/1728 = 227 cubic feet.
And the volume of steel in the transverse trusses was 3768 x 39.7/1728 = 86.6 cubic feet.
So the overall per floor volume of steel in the floor support system was
150 + 13.3 + 227 + 86.6 = 477 cubic feet.