180 PRACTICAL STRUCTURAL DESIGN 



49 000 



Depth of tables (assuming 3 used) = 5 ^77 = 1.275 ins. 



o X o X ItKX) 



Use 1 T 5 B x 3 ins. 

 Assuming three rivets in each table, stress in each rivet = 



49 000 



- = 5450 Ibs. Use three |-in. rivets in each table. 

 y 



Thickness of plate for bearing against rivets = f in. 

 Thickness of plate for shear = J^ - = 0.614 in. 



J.U,UvMJ X o 



49 000 



Thickness of plate for tension = . r = 0.59 



16,000 x (8 in. - 2.8 in.) 



in. Make plate f in. thick. 



,, , . . 1.3125 in. + 0.625 in. 49,000 



Moment of rotation of tables = - 5 - X k 



= 15,800 in. Ibs. 



Stress in bolts = ^^ = 4520 Ibs. 

 o.o 



Add stress due to pin in bolster = j x \ X 800 Ibs. x 8 ins. = 

 800 Ibs. 



Total stress in two bolts = 5320 Ibs. Use two f-in. bolts. 



Using two f-in. diagonal bolts, the horizontal component in 

 the bolster will be as in Fig. 104, requiring one pin. 



Distance required between tables for shear = ' - = 



3 x 8 x 150 



13.6 ins. Use 13f ins. 

 Fig. 106 illustrates a practically perfect joint, except that it 



is not cheap. The chord and batter post stresses are transmitted 



to the gusset plates by 

 means of lag screws acting 

 in shear. There is no ec- 

 centricity of stresses and 

 consequently no secondary 

 stresses. With good in- 

 spection the lag screws will 

 fit closely. The holes in the 

 steel plates for the lag 



Holes in plates for 'lag screws drilled to n'diam. SCreWS are drilled -fa in. 

 Black spots show tag screHsmnearpla*. forger diameter than the 

 ,0pen circles snow lag screws in far plafe. 



diameter of the screws. The 



T^ 1 Oft 



plates should be fitted to 

 the timber and the holes marked, after which they are bored 



