The aim of this study is to develop some practical method of calculations as regard to the structural behaviour of prestressed concrete structures in plastic range.

In part 1, fundamental relations among bending moment, curvature, stress and strain of prestressed concrete member are shown. The above relating have been deduced using so-called the e-function method.

In part 2, a numerical calculation, which has been performed for a rectangular prestressed concrete beam with single arrangement of prestressing bar, is shown. The results of the calculation indicate that: (i) the value of yielding moment varies in accordance with the quality of steel, and ductility of member is influenced by the shape of stress-strain curve of steel. (ii) the values of curvature, stress and strain of materials corresponding to the yielding moment are sometimes too high from the practical point of view.

* Manuscript received on May 29, 1965.
** Research Member of B.R.I , Ministry of Construction