30 



RESISTANCE OF MATERIALS 



of two rectangles a large rectangle of base B and height H, and a 

 smaller rectangle of base b and height h. Consequently the / for 



either figure, with 

 respect to its cen- 

 troidal axis G G, 

 is given by 

 I== BH* bh* 

 12 " 12* 

 Similarly, the 

 figures shown in 

 Fig. 27 may each 

 be regarded as the 

 sum of two rect- 

 angles, and hence 

 the / for either 

 of these figures with respect to its cen troidal axis GG is given by 



B* W m 



12 h !2 



For the angle, or tee, shown in Fig. 28 the / about the base line 

 00 is the sum of the J's for the two rectangles into which the figures 

 are divided by the dotted lines ; that is, 



BH 8 bh* 



- 





B 



_J 



FIG. 28 



< ----- b ----- 



o 



The position of the cen troidal axis GG may then be determined 

 by taking moments about the base 00. That is to say, since the 



