The average intensity of pressure is 28.25 × 18 = 508.5 pounds per square inch.
The load transmitted to the ranger is 6,000 pounds.
Similarly the load transmitted to the ranger from the panel above is 6,890 pounds.
The total distributed load on the ranger is 12,890 pounds.
If b is the vertical dimension of the ranger and d is the horizontal dimension in inches, then from the beam theory, using f as 1,200 pounds per square inch, bd2 = M
200, in which M is expressed in inch-pounds. The maximum bending moment is
Wl
8 = 12,200 × 8 × 12
8 = 155,000 inch-pounds
Therefore, bd2 = 775.
An 8 × 10 inch beam will fulfill the conditions closely. Substituting these dimensions in the beam formula
f = Mc
I = 155,000 × 5 × 12
8 × 1000
= 1,160 pounds per square inch tension in outer fiber. The results of the computations for other rangers are shown in Table 60.