CANTILEVER AND SIMPLE BEAMS 35 



311. A floor is supported by wooden beams, 2 x 10 inches section 

 and 12 feet span, spaced 16 inches between centers. Find the safe 

 load per square foot of floor area if the maximum fiber-stress is 800 

 pounds per square inch. 



312. A floor is to support a total load of 200 pounds per square foot 

 of floor area. Determine the proper size for the steel I-beams, 12 feet 

 span and spaced 5 feet apart between centers, to support this floor 

 with a factor of safety of 4. 



313. A beam has a section like Fig. 19, with \ = 5 2 = 6, t l =t 2 =l, 

 t = |, and d = 10 inches. Compare its strength to resist bending when 

 placed like this: I ; and like this: HH . 



314. A cast-iron simple beam of 12 feet span has a section like Fig. 20, 

 with = 1, d=6, and 6 = 8 inches. Find the factors of safety against 

 tension and compression under a total uniform load of 5000 pounds. 



315. Select the proper steel I-beam for Problem 193 for a fact or of 

 safety of 6. 



316. Select the proper steel I-beam for Problem 203 for a factor of 

 safety of 6. 



KUPTURE 



317. Find the length of a cast-iron cantilever beam 2 inches square 

 that will break under its own weight. 



318. A cast-iron cantilever beam 2x4 inches section area and 

 12 feet long, carries a concentrated load at its free end. Find this 

 load to break the beam, considering the weight of the beam itself. 



319. Calculate the length of. a wooden cantilever beam 1x2 inches 

 section area that will break under its own weight. 



320. Determine the total uniform load to rupture a cast-iron canti- 

 lever beam 2 inches square and 10 feet long. 



321. Compute the size of a square wooden simple beam 9 feet span 

 that will break under its own weight. 



322. Determine the concentrated load placed at the middle that 

 will rupture a wooden simple beam 2x4 inches cross-section and 

 12 feet span. Neglect weight of beam. 



323. 'A cast-iron simple beam 12 feet long and 3 inches square 

 carries two equal loads at quarter points. Find the loads that will 

 rupture the beam, neglecting its own weight. 



