240 



FIEE-BOX GIRDER STAYS. 



Then by substitution we get 



750 X rf2 X « 



{W-P)xDx WP 



I 



and this is the Board of Trade equation 



750 xcPxt 



(W-P)xDxWPxL 



in which the constant factor c = 750 for girders with three 

 supporting bolts and subject to the foregoing conditions 

 remains the same whether two or three supporting bolts are 

 used. 



And lastly we have the case of the 



GIRDER WITH FOUR SUPPORTINa BOLTS. 



K -- 5 



-->. 



f i --if— J ^ —X- J t -— ^— -^ L—-^ 



Then assuming that the length of the girder and the total 

 weight supported by the bolts remains the same as in the 

 previous cases, then the " Moment of Rupture " at the centre 

 of the girder will be equal to 



^r -^t;x^ZxAZ lie X II X \l \ic x llx\l ^^ox^lxll 



1\1 — r + :: + I + 



I 



I 



I 



I 



I I I I 



wxl wxl IV X I wxl 



M = + -H -H 



40 20 20 40 



