COLUMNS AND STRUTS 47 



for the structural steel piston-rod if it is 5 feet long and subject 

 to shocks. 



440. The diameter of a piston is 40 inches and the maximum steam 

 pressure 110 pounds per square inch. The wrought-iron connecting- 

 rod has a rectangular cross-section and a length of 12J- feet. Find 

 the dimensions for the cross-section of the rod for a factor of safety 

 of 10. 



441. A hollow, circular, steel column 28 feet long with fixed ends 

 is to support a steady load of 30 tons. If the external diameter is 6 

 inches, determine the thickness of the metal for a factor of safety of 4. 



442. A steel I-beam 15 inches deep, 50 pounds per foot, is used as 

 a column 10 feet long with fixed ends. Find the load it can bear 

 with a factor of safety of 4. 



443. A column 20 feet long with fixed ends is formed by joining 

 the legs of two 10-inch steel channels, 30 pounds per foot, by two 

 plates 10 inches wide and ^ inch thick, section as shown in Fig. 27. 

 Find the load for a factor of safety of 4. 



444. A steel column 20 feet long with fixed ends is used in a bridge 

 under an axial compression of 240,000 pounds. The section is like 

 Fig. 28, the 12-inch channels weigh 20.5 pounds per foot, I = 16, and 

 t = | inch. Determine the factor of safety. 



445. Two 8-inch steel I-beams, 25.25 pounds per foot, are joined 

 by lattice work to form a column 20 feet long with fixed ends. How 

 far apart must the beams be placed, center to center, in order that the 

 column shall be of equal strength to resist buckling in either axial 

 plane ? What load can the column then stand with a factor of safety 

 of 5? 



446. Solve Problem 445 with two 9-inch steel I-beams, 21 pounds 

 per foot. 



447. A steel column 14 feet long with square ends is formed by 

 two 12-inch steel channels, 20.5 pounds per foot, placed back to back. 

 Determine the proper spacing of the channels and the load the column 

 will then carry with a factor of safety of 4. 



448. Find the load for a hollow cast-iron column with fixed ends, 

 16 feet long, outside dimensions 4x5 inches, inside dimensions 3x4 

 inches, if the eccentricity of the load is 1J- inches and the factor of 

 safety is 6. 



