STRESS IN BARS DUE TO WEIGHT H9 



Stress in a Bar Due to its Own Weight: 



Let b = breadth of bar in inches ; 

 h = depth of bar in inches ; 



w = weight of bar per lineal inch = 0.28 b h' ; 



p 



f z = = direct unit stress. 

 b h 



We will also have 



!Vi = V* h; 

 MI = y& w I 2 ; 

 P = f 2 b h. 

 Substituting in (75) we have 



yi " **!+>- 



12 " 10 X 28,000,000 



4,900,000 h 



= ~7h^ (76) 



/ 2 + 23, 000, 000 (^J 



where f is the extreme fibre stress in the bar due to weight, and is 

 tension in lower fibre and compression in upper fibre. 



If the bar is inclined, the stress obtained by formula (76) must be 

 multiplied by the sine of the angle that the bar makes with a vertical 

 line. 



Formula (76) is much more convenient for actual use than for- 

 mula (75). 



Diagram for Stress in Bars Due to Their Own Weight. Tak- 

 ing the reciprocal of (76) we have 



23,000,000 



+ 



and 



4,900,000 h 4, 900,000 h 



(77) 



' 



