The behaviour of prestressed concrete sections near the maximum moment

Abstract

Summary Tests are described in which prestressed concrete sections were tested in pure bending in such a way that the complete moment-curvature curves could be obtained. The special requirements of the testing equipment are discussed and it is shown that there are descending branches to the moment-curvature curves of both underand over-reinforced sections. A theoretical discussion is given of the conditions of maximum moment of underand over-reinforced sections, including the cases of combinations of bending moment and axia load. The analysis is based on the stress-strain curve of concrete and it is shown that the conventional curves are not the true stress-strain curves of concrete. Attempts to obtain the actual curves are described; the parameters thus obtained are used in the analysis and give close agreement with measurements of maximum bending moments and curvatures in actual tests.