DESIGN OF STRUCTURES 239 
‘through the gusset and stringer plate to take the load from the gusset 
and transfer it to the boom. 
one The axes of each member (boom included) should meet at a 
4 ©) The rivets in each member should be symmetrically grouped 
Si eut its centre line. 
(d) A tension member should not be weakened to a greater extent than 
one rivet hoie. 
7 (e) The rivets should be spaced at a convenient and uniform pitch. 
_ Those in the web members should not be permitted to upset the 
uniformity of pitch of the boom riveting. 
. (f) The centres of the rivets should not be less than three diameters 
_ apart, or closer to the edge of the plate than 14 diameters. 
_ Too often in actual practice the above conditions are not all com- 
with. Sometimes a compromise has to be made, but with a little 
oa and ingenuity much i! be done towards satisfying all the con- 
itions. 
213. End Posts.—The end struts of bridge trusses are termed end 
_ posts. They have to carry the whole reaction due to the load on the 
girder, and are therefore of more massive construction than the ordinary 
Fia. 366. 
struts ; in fact, they are frequently of similar cross section to the com- 
pression boom, 
Details of two inclined posts.are shown in Figs. 366, 367, and 368. 
A vertical end post is shown in Fig. 384, p. 254. In some inverted 
_ trusses, however, the end member is a tie, which may be of the usual 
214. Bearings.—Beneath the feet of the end posts are placed the 
bearings. An example of a roller bearing is shown in Fig. 369, which 
