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this mucli tliongli he will stale as the result of botli theoretical investigation anil 
many practical cases of designing, that when rivets are proiiortioncd for bending they 
u'ill have wore than sufficient strength to remt shear. Sharp edges on rivet holes will 
certainly cut tlio l.ivet.s， but this is not shear proper ; and it may be possible that 
tlierc is a certain kind (f fixedness about a well drivon rivet, which will make tlio 
bending moment less than its calculated value, but this fixedness is obtained by 
a high initial tension, which increases the stress on tlie tension side of the rivet 
subjected to bonding. As tins lmtial tension crtimot be measured or calculntecl, it is 
safer to assume no reduction of bending moment ou account of its existence. 
Comitersinking is a term useJ to clonotc the sinking of rivet heads into the 
plate so as to make tliem flusli witli its surface. Tlio least allowable depth for the 
countersiuking is a quarter of «"in incli, ami the least thickness of plate used for this 
purpose should be three eighths of an inch : for rivets over three quarters of an inch 
in diameter these dimensions should l)e increased by an eighth of an inch. liivets 
may be counter sunk at oue or both ends. 
Making parallel rows of rivets staggoretl avoids unnecessary weakening of tlic 
parts rivetted togelher. 
There lias been much discussion as to wlietlicv punched or drilled holes aro 
preferable, the general conclusion being that drilled 1101 es weaken the plates less, 
and, when slightly countersunk do not iuevease the shear upon the rivets ; but that 
punched holes tu.e so much more economical as regards shop work that, when properly 
made, they aro pi.efei.able to drilled ones. Tlio improvements made of late years ia 
ri vetting machines have increased the efficiency of work with punched rivet holes. 
Should for any reason it ever be necessary in bridge designiug to put a rivet 
through a plate whose thickness is greater than the diameter of the rivet, the rivet 
liole should bo drilled. Machiuo rivettiug is preferable to hand rivettiug, but there 
are cases when tlie latter lias to be employed. Field rivettiug is always inferior to 
shop rivettiug, so should l)e avoided as much as possible in making designs. "Wlien 
a stress is transmitted from one plate through one or more plates to another plate, 
the number of rivets must be increased. The rule given by Dr. Weyrauch is that 
“for every single shear connection the indirect force transferred ce requires for m 
intermediate plates m +1 times as many rivets as for direct transferrence f, . 
Keeping this in view tlio designer ’will avoid using more than one flange plate in 
floor beams or more than on。 plate for covering the channels of top chords. • 
