depth is merely 3 inches. The top reinforcement, therefore, is placed in practice actually at, if 

 not below, the neutral axis, where it could not possibly take any tension, if such existed. 

 In lieu of the fact that the reinforcement is ineffective to take tension at this point, and where- 

 as it is known that the concrete alone is negligible as regards taking tensile stresses, it is rea- 

 sonable to suppose in the absence of any but very fine cracks that very little, if any, such ten- 

 sion exists. 



r 



T 



Fig. (6) The dash lines indicate the theoretical location of the tensile stresses in a contin- 

 uous beam construction. 



Fig. (7) The dash line indicates the theoretical location of the tensile stresses in flat arch 

 construction. 



(3) In a series of tests to determine the efficiency of "Steelcrete" mesh in flat arch con- 

 struction, conducted during the spring of 1911 by the Materials Testing Laboratory of the Car- 

 negie Technical Schools, Pittsburgh, Pa., these slabs were carefully observed. The above-men- 

 tioned points were every one confirmed. In addition tie rods had been placed connecting the I- 

 beams supporting the slabs, these rods serving as the only connection between the beams and 

 located immediately outside the arch. It was impractical to gauge the tension in the tie rods due 

 to the enormous thrust of the arches, but that they behaved as if under high tensile stress was 

 admitted by all bystanders. A sharp metallic ring would be noted when the tie rods were struck 

 with anything solid. 



16 



