32 



KANSAS UNIVERSITY QUARTERLY. 



the temporary supports, or on the lintel in case of masonry, increases 

 as the beam or masonry is built up to a height H^ and then decreases 

 from H,i to some height Hg where it is zero, and for this latter 

 height the temporary supports or the lintel may be taken away without 

 affecting the stability of the wall. 



Let the figure represent a brick wall spanning an opening. 



H— any height in feet of wall over opening. 



Hn=height in feet of wall producing maximum load on or stress 

 in lintel. 



Hs ^height in feet of wall which is self- supporting. 



S=span in f^et. 



t=^thickness of wall in feet. 



q=:vv€ight in lbs. per cub. ft. of masonry. 



W=total weight of wall over opening. 



R=modulus of rupture in lbs. per sq. inch. 



The weight of the wall over the opening, 



W-rq S t H (i). 



and the moment of this weight about any point of the beam varys 

 directly with H for a given wall. This latter is represented by the 

 line OB in the figure. 



When the wall is self-supporting we have from resistance of mate- 

 rial one-twelfth of the weighth of the wall over the opening multiplied 

 by the span equals one-sixth of the tensile strength multiplied by the' 

 thickness and by the square of the height of the wall or 

 -^\ (q S t H,) S=.i (144 R) t H,-^ (2). 



