In this method of treating the rectangular slab, the concrete in tension is not considered to be of any value, as is the case in all accepted methods.

Some years ago the writer tested a number of slabs in a building, with a load of 250 lb. per sq. ft.  These slabs were 3 in. thick and had a clear span of 44 in. between beams.  They were totally without reinforcement.  Some had cracked from shrinkage, the cracks running through them and practically the full length of the beams.  They all carried this load without any apparent distress.  If these slabs had been reinforced with some special reinforcement of very small cross-section, the strength which was manifestly in the concrete itself, might have been made to appear to be in the reinforcement.  Magic properties could be thus conjured up for some special brand of reinforcement.  An energetic proprietor could capitalize tension in concrete in this way and “prove” by tests his claims to the magic properties of his reinforcement.

To say that Poisson’s ratio has anything to do with the reinforcement of a slab is to consider the tensile strength of concrete as having a positive value in the bottom of that slab.  It means to reinforce for the stretch in the concrete and not for the tensile stress.  If the tensile strength of concrete is not accepted as an element in the strength of a slab having one-way reinforcement, why should it be accepted in one having reinforcement in two or more directions?  The tensile strength of concrete in a slab of any kind is of course real, when the slab is without cracks; it has a large influence in the deflection; but what about a slab that is cracked from shrinkage or otherwise?

Mr. Turner dodges the issue in the matter of stirrups by stating that they were not correctly placed in the tests made at the University of Illinois.  He cites the Hennebique system as a correct sample.  This system, as the writer finds it, has some rods bent up toward the support and anchored over it to some extent, or run into the next span.  Then stirrups are added.  There could be no objection to stirrups if, apart from them, the construction were made adequate, except that expense is added thereby.  Mr. Turner cannot deny that stirrups are very commonly used just as they were placed in the tests made at the University of Illinois.  It is the common practice and the prevailing logic in the literature of the subject which the writer condemns.

Mr. Thacher says of the first point: 

“At the point where the first rod is bent up, the stress in this rod runs out.  The other rods are sufficient to take the horizontal stress, and the bent-up portion provides only for the vertical and diagonal shearing stresses in the concrete.”

If the stress runs out, by what does that rod, in the bent portion, take shear?  Could it be severed at the bend, and still perform its office?  The writer can conceive of an inclined rod taking the shear