1 



LXXIV. W. H. WARREN AND g. H. BARRACLOUGH. 



= the portion of the entire weight of the wall which is 



self-supporting, and: — 



1 - — = the portion which requires support. 

 Hi 



The total height to be supported is: — 



1 ' x ; h 



h I 

 This is a maximum when h! = — or the expression 



h) 4 



The maximum load in the beam equals the weight of a quarter of 

 the height of a self-supporting wall. 



I 2 , h I 2 



Since h = -— and h' = — . • . h' = — 

 2/ 2 4/ 



This gives the height of the wall producing the maximum load on 



the girder. 



Referring to the example it appears that since 20 feet is the 

 height of a wall which would support itself, assuming that the 

 value of the modulus of rupture is 10 lbs. per square inch; the 

 height of the wall producing the maximum load upon the beam 

 is 10 feet. 



It is clear that the practice of assuming that the whole height 

 of brickwork above the girder over an opening is actually carried 

 by the girder is incorrect; moreover the girder should be designed 

 to carry whatever load is actually brought upon it depending on 

 the transverse strength of the brickwork, not as a beam supported 

 at each end and loaded uniformly along its length, but as a beam 

 fixed at the ends, having its maximum bending moment at the 

 points of support. 



