Cold Drawn Prestressing Wire

In reinforced concrete design it is generally assumed that the strain in the steel reinforcement is equal to the strain in the concrete immediately surrounding it. This is substantially true in zones of compression but, in the parts subject to tension, the working stress in the steel is usually high enough for the strain to be more than the surrounding concrete can withstand without cracking. The size of the cracks formed in this way and their spacing along the reinforcement depends primarily on the bond but is also affected by the strain in the steel, the tensile strength of the concrete and its modulus of elasticity.

Sir-The writer found this paper of the greatest value and would be glad if the author could amplify some points.

The presence of the slab on the compression side of a T-beam permits the use of a large amount of tensile, steel in the rib. In continuous spans, however, the reverse moment at the support is usually comparable in magnitude with the span moment, and so also calls for a considerable amount of tensile steel; but as the slab is now not on the compression side the rib concrete often requires the assistance of compression reinforcement (Fig. 1). F.H. Blake