RELATIVE BEXDLXG STRENGTH OF CROSS A RMS 



43 



will be the depth (d) of the rectangular j^jortion of the section, which for the 

 smaller will he p + (D — r), ov 



3.6688 + (4 - 4) = 3.6688" 



Computation II. Moment of Inertia of Top Segment of Nominal {3\" x 

 4ys") Section between Pinholes: 



As this computation was made in exactly the same manner as Computa- 

 tion I, only the results are here shown: 



d = 3.8593" 

 g - 0.1317" 

 .4 = 0.7168 sq. ins 

 IT = 0.0053 



Computation III. Moment of Inertia of Top Segment of Minimum {3y&" x 

 4^_") Pinhole Section: 



It will be noted in Fig. 10 that the top segment is divided into four parts: 

 the small segment {Ti) at the top of the pinhole, the rectangular portion 



Fig. 10 — Crossarm pinhole section. 



Ri, with a width of bi and a depth of di, and two portions designated Tc. 

 The purpose of this computation is to determine the moment of inertia of 

 one of the Tc portions with respect to its gravity axis parallel to its base. 

 The moment of inertia of the two Tc portions about the axis BB ma}' be 



