JOINTS AND CONNECTIONS 



167 



Designing Joints 



In Fig. 98 is shown one method for making the joint LO. The 

 computations, in order, are as follows: 



Depth of toe, = 45, therefore n - 1200 X 0.45 - 540 Ibs. 

 per sq. in. 



35,950 



Required area in bearing 



1200 



= 66.6 sq. ins. 



Required depth of face = g- = 8.33 ins. 



The above operations involved finding the fiber stress in com- 

 pression per sq. in., dividing the total load to find the required 

 area and then dividing the area by the width of the chord to find 

 the required depth of the end of the brace. This depth being 

 normal to the angle of the brace we divide it by the secant 

 of the angle and find that the vertical depth of cut in the chord 

 = 8.33 -s- 1.4141 = 5.9 ins. The depth of the cut should be such 

 that below the point there will be enough area left in the chord 

 to carry the tension. Neglecting the middle filler, the width of 



25 000 

 the chord is 6 ins., so the depth = 6x ' 160 Q = 2.6 ins. Practically, 



the depth of the cut should not be more than one-half the depth 

 of the chord, so another detail should be selected. 



We can, at this point, assuming the computed depth of cut is 

 correct, proceed to find the length of chord projection for shear 

 and find the center line 

 of support; merely to 

 show in detail the nec- 

 essary computations. 

 For this purpose the 

 depth of the vertical 

 cut in the chord will 

 be assumed to be four 

 inches. 



Forces are assumed 

 to be concentrated, or 

 to act along the center 

 lines of stressed mem- 

 bers. In the end piece the compression is all acting on the square 

 end face, 4 ins. deep x 8 ins. wide and the center lines of the 



