294 



TKSTING OF STRUTS. 



Next, using Johnson's parabolic formula, 

 P = A [34,000 - 0-67 (I* 



= 6-5 [34,000 - 0-67 . A'|^ 



= 198,0001bs. 

 = 88-4 tons. 



which is fairly near the actual load. 

 In Gordon's formula, 



J! A 



P = - J 



! 



00 



T3 



a 



I 



60000 



50000 



40000 



30000 



20000 



10000 



\ 



RATIOS 1 20 40 60 80 100 120 140 T60 180 



* 



FIG. 152. 



CURVES SHOWING THB CRIPPLING STRESS - FOR WROUGHT IRON STRUTS 



A 



HAVING DIFFERENT RATIOS ~r (ROUNDED ENDS). 



it 

 P 5T 2 E fc 2 



E Euler's Curve from equation -j = 



P Z 2 



J Johnson's Parabolic Curves from = 36,000 - T08 73 



T> O (\C\C\ 



R Bankine's Curves from equation -j = ^ 



. i i -Li 



-j 



~ 



i^ooo 



