STRESS-STRAIN RELATIONSHIP OF CONFINED HIGH-STRENGTH PLAIN AND FIBER CONCRETE

The complete stress-strain curves generated experimentally for high-st rength plain and fiber concretes confined by transverse ties are repor ted in this paper. The test parameters include tie diameter, tie spaci ng, concrete core area, and casting direction of specimens. Test resul ts indicate that the initial tangent modulus and initial Poisson's rat io of the concrete are not affected by confinement. However, confineme nt enhances both the peak stress and strain at peak stress. Vertically cast confined fiber concrete exhibits larger strain at peak stress an d has higher postpeak ductility compared to the corresponding horizont ally cast specimen. Vertically cast confined nonfiber concrete also ha s larger strain at peak stress, but ductility is hardly improved over horizontally cast specimens. Based on test data, an analytical model i s proposed to generate the complete stress-strain curves of high-stren gth concrete confined by lateral ties. The proposed model has been fou nd to agree well with the stress-strain curves generated experimentall y.