JOINTS AND CONNECTIONS 



153 



to one-fourth the thickness of the middle piece, plus one-half the 

 thickness of the outer piece, or splice pad. The load was half the 

 total tension and each bolt carried its proportionate share. This 

 is the method found in the majority of text books. It called for 

 very large bolts and made a heavy, awkward-appearing connec- 

 tion. It is the proper method to use for pin connections (Fig. 86), 

 the size of the pins being also figured for direct shear and the 

 computations for end lengths and distances between bolts being 

 computed as in the examples following. 



The method for fish-plate joints used by the writer and shown 

 in Fig. 91 is the modified fish-plate joint proposed by Mr. Dewell, 



Top View 

 Fig. 91. 



and the strength of the bolts is based on the table on page 139. 

 45,000 



Net area required 



1000 



= 28.1 sq. ins. 



Assume the splice pads to be 2 ins. thick and 8 ins. wide, which 

 gives an area of 32 sq. ins. Two 1-in. bolts will occupy a space 

 2 ins. wide, with a bearing of 4 sq. ins., which will bring the splice 

 pads down to the proper net size. 



From the table on page 139 the strength of 1-in. bolts in double 

 shear with 2-in. fish-plates - 2460 Ibs. 



45,000 



Number of bolts required 



18.3. There should be an 



even number of bolts and we should not use a higher stress than has 

 been shown to be safe, so this points to the use of 20 bolts. This 

 means 20 bolts on each side of the joint, for the entire pull must 

 be carried into the fish-plates and then be carried by another set 

 of bolts back from the fish-plate into the main piece on the other 

 side of the joint. The total number of bolts therefore will be 40. 

 There is a transverse tension in every piece which tends to cause 



