Its tensile strength is higher than that of steel.
The safe tensile strength of Portland cement concrete would be something like one-tenth of its compressive strength, and might be far less.
Ewing has shown that it is diminished and may even be reversed by tensile stress.
Some experiments were next undertaken with the view of ascertaining how far magnetic changes of length in iron were dependent upon the hardness of the metal, and the unexpected result was arrived at that softening produces the same effect as tensile stress; it depresses the elongation curve, diminishing the maximum extension, and reducing the " critical value " of the magnetizing force.
To meet tensile stresses the steel is nearly always inserted in the form of bars running along the beam.
