Budding of Deep Beams. 221 



fixed in a delicate torsiometer which was capable of trans- 

 mitting small torques of known amount, about the longi- 

 tudinal axes of the specimens. The angles of twist corre- 

 sponding with different gradations of torque were noted and 

 plotted one against the other, and the curves are reproduced 



T 

 in fig. 2. The torsional rigidity Kn is given by Kn= ^ Z, 



T 

 where -pr is the slope of the curve and I is the length of the 

 6 



corresponding strip under test. 



Fisr. 2. 



Angles of ti/s/st - (l - i n radian) 



The values of the rigidities for each of the five strips are 

 given in the table (below) and also values of P calculated 

 by the expression (1) and corresponding with two lengths 

 for each strip. It may be noted that no dimensions of the 

 strips other than the lengths under test are involved in 

 equation (1). 



The buckling loads were obtained experimentally as 

 follows : — each strip was firmly gripped in a vice and pro- 

 jected horizontally outwards with its sides vertical. The 

 load was transmitted by weights suspended by a fine wire 

 which passed through a small hole drilled through the mid- 

 depth of the specimen near its end. When the buckling 

 load was almost reached the specimen could vibrate slowly 

 from side to side and finally came to rest in the central 

 position. When the buckling load was just past, the 



