189.
| Name. | Span. | Rise. | Width. | Rad. of Arch. | Scantling of Arch. |
|---|---|---|---|---|---|
| Bamberg, | 208 | 16.9 | 32 | 422 | 13½ × 15½ |
| Scharding, | 194 | 18.8 | 25 | 258 | 12½ × 15½ |
| Vilshoven, | 179 | 11.1 | 27 | 378 | 13½ × 15½ |
| Freysingin, | 153 | 11.6 | 25 | 246 | 12½ × 14½ |
| Ettringin, | 139 | 8.0 | 25 | 305 | 12½ × 15½ |
| Ersingin, | 126 | 7.0 | 25 | 285 | 11½ × 14½ |
| Augsberg, | 114 | 10.6 | 25½ | 158 | 12½ × 14½ |
| Neucettringin, | 103 | 6.8 | 25 | 200 | 13½ × 15½ |
The last column shows the scantling of the arch timbers; these being placed three deep, in spans of less than 150 feet; and in larger spans, 3 deep at centre, and 5 deep at ends. Mr. Weibeking’s formula for determining the scantling of ribs, is as follows:—
W × (S/2)2
Rn.0011 = Scantling in sq. ft.
Where R is the rise of the arch;
n, the number of ribs;
W, width of bridge;
and S, span of bridge.
Example.—Required the scantling of the ribs of a bridge of 300 feet span, 20 feet wide, and 30 feet high. The formula becomes,—
20 × 22500
30 × .0011 = 16½ sq. feet of