336 DOCK ENGINEERING.
The cross-sectional area is as follows : —
Web, . . 45 x ^ = 18 square inches.
Two plates, each, 25 x ^ = 20 „
» >> 8x^ = 6’4 „
Four angles, 4 x3 x ^= 10-56 ,,
54-96
Say, 55 square iuches. From formula (51) we have—it being noted that
the flanges are symmetrical about the centre of section—
7 J - J A ~ I
175,000 + 175,000 x 17 x 23’3
- 55 - 21,808
= 3,182 ± 3,178 Ibs.,
that is, 2’84 tons per square inch on the outer flange and 4 Ibs. per square
inch on the inner flange.
k
i
Hat 9"x%öf
Angles |
4\3\ 8/20" ;
25-1
of Pressure
Centre
T’
Fig. 275.
web I
Hl
Now, take the rib at a depth of 12 feet 9J inches, and deal with section
3 - 3, shown in fig. 275. In this case the inner plating is the water-
bearing surface, whose radius = 51 feet, nearly.
Water pressure = 2’6 x 12’8 x 64 = 2,130 Ibs.,
F = R= 2,130 x 51 = 109,000 Ibs.,
in round numbers.
Cross-sectional area of rib—9 x ^ = 3’6 square inches.
39 x X = 15’6 „
31 x ^ = 12’4
8x5J = 3’2 „
Four angles, 4 x 3 x ^ = 10’56 „
45-36
Say, 45 square inches. In this case the flanges are not symmetrical about