LXXII. W. H. WARREN AND S. H. BARRACLOUGH. 



the better results, but even after twelve months the lime mortar 

 was weaker than the bricks. 



In testing the beams built in cement mortar after about six 

 months hardening in air, the greater strength of the mortar enabled 

 them to resist the horizontal shearing stresses much better, and 

 with the stronger of the two cement mortars the bricks were the 

 weaker, whereas the weaker mortar appeared to be just about as 

 strong as the bricks. This is seen by the failure by rupture of the 

 bricks and shearing in tests Nos. 15 and 16, as well as the direct 

 tests for shearing and adhesion, giving about the same results as 

 the shearing stress developed in the beams. 



The two smaller beams built in cement mortar and tested after 

 about twelve months, gave results showing the mortar to be stronger 

 than the bricks. The modulus of rupture calculated from the 

 results obtained in testing the cement mortar beams has the 

 ordinary meaning, since in all cases failure occurred by rupture 

 of the bricks. The deflections observed with the various loads 

 applied in the cement mortar beams are plotted in Fig. 7, and the 

 curves are more or less parallel up to a total load of two tons, but 

 the coefficient of elasticity is irregular. 



It is necessary to know the transverse strength of brickwork in 

 order to determine the load which will be brought to bear upon 

 a beam spanning an opening and carrying a brick wall. The 

 brickwork as it is gradually built over the girder increases in weight 

 directly as the height, but its resistance as a beam increases as 

 the square of the height. The height at which it will just support 

 itself depends upon its transverse strength, thus 1 : — 

 Let I denote the span of an opening. 



„ h the height of brickwork which is self-supporting. 



,, t the thickness of the brick wall. 



„ w the weight of a cubic foot of brickwork. 



„ f the. modulus of rupture in pounds per square inch. 

 The bending moment occurs near the points of support of the beam, 



1 See Baker's Masonry Construction, and Engineering, Vol. xiv. 



