STREKGTH OF BEAMS 



57 



112. Find the section moduli for the sections given in problems 58, 60, and 62. 



113. Design a steel I-beam, 10 ft. long, to bear a total uniform load of 1500 Ib./f t., 

 including its own weight. 



114. A built beam is to be composed of two steel channels placed on edge and 

 connected by latticing. What must be the size of the channels if the beam is 

 to be 18 ft. long and bear a load of 10 tons at its 



center, for a working stress of 16,000 lb./in. 2 ? 



115. Compare the strength of a pile of 10 boards, 

 each 14 ft. long, 1 ft. wide, and 1 in. thick^ when 

 the boards are piled horizontally and when they are 

 placed close together on edge. 



116. Design a rectangular wooden cantilever to 

 project 4 ft. from a wall and bear a load of 500 Ib. 

 at its end, the factor of safety being 8. 



117. A wooden girder supporting the bearing par- 

 titions in a dwelling is made up of four 2-in. by 10-in. joists set on edge and spiked 

 together. Find the size of a steel I-beam of equal strength. 



118. A factory floor is assumed to carry a load of 200 lb./ft. 2 and is supported 

 by steel I-beams of 16-f t. span and spaced 4 ft. apart on centers. What size I-beam 

 is required for a working stress of 16,000 lb./in. 2 ? 



