A series of compression tests were conducted on 3 × 6 in (76·2 × 152·4 mm) cylindrical specimens using a modified testing method that gave the complete stress–strain behaviour for high-strength concrete with or without tie confinements. Empirical equations are proposed to represent the complete stress–strain relationships of unconfined and confined high-strength concretes with compressive strength exceeding 10 kip/in2 (69 MPa). Various parameters were studied and their relationships were experimentally determined. me proposed empirical stress–strain equations are compared with actual cylinder tests under axial compression, and are found to agree well.

This paper explores the load-deformation behaviour of plain andjbrous high-strength reinforced concrete slender columns from zero load until failure. The proposed empirical stress-strain equations given here for high-strength and high-strength steel fibre concretes were used as material properties to modify the computer programs of biaxially loaded slender columns previously developed. The new computer program can evaluate the complete biaxial load-deflection and moment-curvature relation-ships of slender columns. A total of nine high-strength and five high-strength steel fibre reinforced concrete columns were tested to compare their experimental load-deformation results with the analytical values derived from theoretical studies. Agreement was satisfactory for both ascending and descending branches of the load- deformation curves.

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