584 THE DESIGN OF STEEL DETAILS. CHAP. XVIL 



Flange Splice. Flanges should never be spliced unless it is impossible to get material of 

 the required length. Flange splices should always be located at points where there is an excess 

 of flange section, no two parts of the flange should be spliced within two feet of each other. Rivets 

 in splice plates and angles should be located as close together as possible in order that the transfer 

 may take place in a short distance. No allowance should be made for abutting edges of spliced 

 members of the compression flange. 



Flange angles should be spliced with a splice angle of equal section riveted to both legs of 

 the angle spliced. Where this is impossible the largest possible splice angle should be used and the 

 difference made up by a plate riveted to the vertical leg of the opposite angle. The number of 

 rivets required in the splice angle on each side of the joint in the angle is given by the formula, 



= /J r (17) 



where / = the allowable unit stress in the flange, A = area of spliced angle, and r = the allow- 

 able stress on one rivet. Rivets which are already considered as transferring the shear may be 

 considered as splice rivets if they are included in the splice angle. 



Cover plates should be spliced with a splice plate of equal section. The number of rivets 

 required in the splice plate on each side of the joint is determined by the above formula if the plates 

 are in direct contact in the same way as for splice angles. Where one or more plates intervene 

 between the splice plate and cover plate which it splices, rivets should be used on each side of the 

 joint in excess of the number required in case of direct contact, to an extent of one-third that 

 number for each intervening plate (see 79, p. 144, and 57, p. 211). 



The above methods for flange splicing apply only when methods (i) and (2) of proportioning 

 sections are used, but may be used with sufficient accuracy when methods (3) and (4) are used. 

 Strictly speaking for methods (3) and (4) splice angles and plates should have moments of inertia 

 about the neutral axis, equal to the moments of inertia of the members they splice, about the 

 neutral axis. An exact analysis for the number of rivets required in splices would give a less 

 number than obtained from above formula. 



Stiff eners. For method of designing stiff eners see 43, p. 58; 52, p. 142; 79, p. 207; 

 79, p. 212; p. 221. 



Pins and Pin Packing. A pin under ordinary conditions is a short beam and must be designed 

 (i) for bending, (2) for shear, and (3) for bearing. If a pin becomes bent the distribution of the 

 loads and the calculation of the stresses are very uncertain. 



The cross-bending stress, /, is found by means of the fundamental formula for flexure, 

 f = M-c/I, where the maximum bending moment, M, is found as explained later; / is the moment 

 of inertia; and c is one- half the radius of a solid or hollow pin. 



The safe shearing stresses given in standard specifications are for a uniform distribution of 

 the shear over the entire cross-section, and the actual unit shearing stress to be used in designing 

 will be equal to the maximum shear divided by the area of the cross-section of the pin. 



The bearing stress is found by dividing the stress in the member by the bearing area of the 

 pin, found by multiplying the thickness of the bearing plates by the diameter of the pin. 



References. 41, p. 58; 90, p. 61; 99, p. 61; 107, p. 62; 39, p. 141; 40 and 41, 

 p. 141; 74, p. 143; 75, p. 143; 76, p. 143; 92, p. 144; 141, p. 145; 142, p. 145; 144, 

 p. 146; 17, p. 209; 18, p. 209; 19, p. 209; 28, p. 210; 52, p. 21 1 ; 54, p. 21 1 ; 136, p. 

 216; p. 219; p. 220; p. 402. 



Details of Pins. Details of bridge pins are given in Table 95, Part II. 



Stresses in Pins. The method of calculation will be illustrated by calculating the stresses in 

 the pin at U\ in (a) Fig. 10. In the complete investigation of the pin U\, it would be necessary 

 to calculate the stresses when the stress in UiUz was a maximum, and when the stress in U\Lz 

 was a maximum. Only the case where the stress in U\ Uz is a maximum will be considered. How- 

 ever, maximum stresses in pins sometimes occur when the stress in UiLz is a maximum, and this 

 case should be considered in practice. 



