154 



PRACTICAL STRUCTURAL DESIGN 



the wood to split along the center line of the bolts. The amount 

 of this tension is one-tenth the longitudinal tension, and the safe 

 allowable fiber stress is one-tenth the safe allowable longitudinal 

 stress. The resultant is a shearing stress and must be allowed for 

 in spacing the bolts. 



The shearing stress is assumed to act at each edge of each bolt 

 so that when a bolt passes through a 2-in. plank it exerts a shear- 

 ing stress on four inches, as shown at (c) Fig. 90. We are now ready 

 to space the bolts and determine the length of the splice pads. 



45,000 



120 



= 375 sq. ins. 



The total shearing area in direct pull = 



375 

 Spacing of bolts for shear = 2Q = 



. . , 45,000 x 0.1 



Spacing required for transverse tension = _ x on y 4 = 



2.34 ins. 



Adding diameter of bolts 



Required spacing of bolts 



1.00 



3.69 ins. 



Bolts will be spaced 3f in. staggered, with double this distance 

 from the ends of the splice pads. 



Top Vijew 

 16, li" Shear Pins 



10, 7 'g Bo/ts 



20, 3 / g "x 3 3 4 Washers Side Elevation. 



Fig. 92 



By using thicker splice pads there would be required a less 

 number of bolts and the spacing would have been closer. It is 

 not pretended that the details here worked out are the most 

 economical, for only the methods are shown. Each designer should 

 work out several details. The bill of material and labor must be 

 made out for each and unit prices applied in order to determine 

 the least expensive detail. 



