A series of compression tests are conducted on 3 in. by 6 in. cylindrical specimens using a modified testing method that give the complete stress-strain behavior for both plain and fibrous high strength concretes with or without tie confinements. The volume fractions of fiber in the concrete are 0%, 0.5%, 0.75%, and 1.0%, respectively. Empirical equations are proposed herein to represent the complete stress-strain relationships of high strength and high strength fibrous concretes with compressive strength exceeding 10,000 psi. Various parameters are studied and their relationships are experimentally determined. The comparison between the experimental and analytical results shows to have good agreement.

The proposed empirical stress-strain equations for high strength and high strength steel fiber concretes are used as material properties to modify the existing computer program of biaxially loaded slender reinforced concrete columns. This computer program evaluates the complete biaxial load-deflection and moment-curvature relationships of slender columns from zero load until failure. A total of nine high strength and five high strength steel fiber slender reinforced concrete columns are tested to compare their experimental load-deformation results with the analytical values derived from the present theoretical studies. A satisfactory agreement is attained for both ascending and descending branches of the load-deformation curves.