234 



FIRE-BOX GIRDER STAYS. 



the " Shearing Forces," because, provided there is sufficient 

 material to resist the '' Bending Moment," there will always 

 be an excess of material to resist the " Shearing Force." 



Now let us consider the four cases for which the Constant 

 c is given in the formulse, for girders having one, two, three 

 or four supporting bolts respectively. And if we take 

 I = the length of the girder, and 

 IV = the total weight supported by the girder, 

 we shall see how the " Moment of E-vipture " is affected by 

 the method of distributing the weight, and first take the 

 case of the 



GIRDEE, WITH ONE SUPPORTING BOLT. 



Then if we take leverages about the abutments, the 

 '' Moment of Rapture " at the centre will be equal to 



I 



I 

 M= icxil 



2" _ 



The stability of a loaded girder depends upon the equality 

 that must always exist between the " Moment of Rupture " 

 = M, and the "Moment of Resistance" of the material =R. 

 So that 31 =^ R. 



Now for a solid rectangular girder the " Moment c\i 



