Section 2. All parts of the structures shall be so proportioned that the sum of the maximum static stresses, in pounds per square inch, shall not exceed the following:
18,000
18,000
Compression in columns
18000
= ----------
L squared
1 + ----------
18000 r squared
With a maximum of 15,000, in which L is the unsupported length of the column, and r is the corresponding least radius of gyration of the section, both in inches.
When a structural steel column is encased in stone concrete properly reinforced, the radius of gyration of the combined section may be used, and the above maximum stress may be disregarded.
For main compression members, the ratio L/r shall not exceed 120, and for bracing and other secondary members 200.