QUESTIONS AND PROBLEMS. CHAPTER IX. 



205 



long, with pivoted ends, which is to carry a concentric load of 

 24,000 Ibs. ? Solve by the Philadelphia laws. 



12. Select an I beam for a column 12 ft. long, pin ends, 

 with a factor of safety of 5, using Rankine 's formula with ' ' Cam- 

 bria" constants. 



13. A 4 in.X4 in. wooden strut, 10 ft. long, lies in a horizon- 

 tal position and carries a load of 20 Ibs. per ft. of length, and is 

 subjected to a direct compression along its axis of 1200 Ibs. Find 

 the deflection at the center and the maximum unit stress. 

 ==1,200,000. 



14. A horizontal compression member with pin ends con- 

 sists of two 10 in. 20 Ib. channels and two 12 in.X 1 /^ i n - plates. 

 The length is 30 ft. and the webs of the channels are vertical. The 

 direct compression is 80,000 Ibs. and there is a concentrated load 

 of 4000 Ibs. at the middle. Find the deflection and maximum 

 unit stress. 



