A trial-and-error approach can be used to determine the maximum allowable load P:

5. If the computed force in member (2) is less than its allowable force, the original assumption has been proved correct — member (1) actually does control the load capacity of the structure.

No further calculations are necessary. The maximum allowable load P for the structure is the value computed in step 3.

The figure shows a diagonal member labeled 1 and a horizontal member labeled fixed to a column on the right at the points A on top and C below. The diagonal member runs between 
points A and B and the horizontal member runs between the points B and C. Joint B is at a distance of 4.3 meters to the left 
of A and 5 meters below A. Joint C is at a distance of 7 meters directly below A. The load at joint B is labeled P and it is 
directed downwards.