174 



PRACTICAL STRUCTURAL DESIGN 



In the diagram in the upper left-hand corner the tensile stress 

 in the bolt is 45,500 Ibs. This at the bottom of the chord is con- 

 verted into a horizontal and a vertical 

 component, shown in the lines AC and 

 CD. First taking the value given by 

 the line AD we find the depth of cut 

 necessary for the vertical component. 



Depth of cut = 



32,000 



Fig. 102. 

 = 3.34 ins. (make it 



ins.). 



8 X 1200 



The bottom of the plate must be large enough to allow a bearing 

 of 350 Ibs. per sq. in. against the side of the wood, the width of 

 the plate being 8 ins. 



32,000 



Length of plate = 



= 11. 4 ins. (make it 11| ins.). 



8 X350 



The thickness of this plate must be found by assuming the 

 edges projecting beyond the collar around the bolt, as cantilevers 

 uniformly loaded. The thickness of the sloping leg in the chord 

 must be figured in the same way. The plate on top of the bracer 

 at the upper end of the bolt must have enough area to keep the 

 bearing down to 350 Ibs. per sq. in. 



The plate must be set far enough from the end of the chord to 

 prevent shearing. 



32,000 



Length for shear = 



= 33.4 ins. (make it 33| ins.). 



8 X 120 



The center of the bolt should be as nearly as possible at the 

 center of the plate, which helps to fix the position of the bolt 

 through the chord and brace, taking into consideration the size of 

 washer at the upper end. Insert a hardwood block in the angle. 



In Fig. 102 (6) is a detail used to prevent the cutting of the 

 bottom chord for washers and to avoid the expense of the special 



