236 



FIRE-BOX GIRDER STAYS. 



D = the distance between the girders from centre to centre, 

 WP = the working pressure, 

 then w;=(Tr-P)xDxTFP, 



and by substituting these factors for iv, in the above equation 

 we get 



(Tf-P) X Z> X J^P = , 



V 



which is the Board of Trade equation, 



500 X c?- X ^ 



{W-P)^D^WP^L 



in which the constant factor c= 500 for girders with one 

 supporting bolt. 



Next take the case of the 



GIRDER WITH TWO SUPPORTING BOLTS. 



^ ^ 



Then assuming that the length of the girder and the total 

 weight on the supporting bolts remain the same as m the 

 first case, then the " Moment of Rupture " at the centre will 

 'be equal to 



I I 



I I 



