The response of reinforced concrete cross-sections to short-term and sustained loads

The paper reports a computer analysis of the characteristic surface for a symmetrical reinforced concrete section in terms of axial load, moment and curvature. The consideration starts from a statement of the surface under short-term load, and is extended in detail to include the effects of cracking, creep and stress redistribution under sustained load. The modes of failure are discussed for both short-term and sustained load, and the influence of the relevant parameters (mechanical proportion of steel ω, relative cover a/h, and ultimate creep coefficient φ_∞) are analysed. A simplified form of surface is demonstrated for short-term load, and modifications of the surface when the load is sustained are derived and assessed.