Stress-Strain Relationship of Confined High-Strength Plain and Fiber Concrete

The complete stress-strain curves generated experimentally for high-strength plain and fiber concretes confined by transverse ties are reported in this paper. The test parameters include tie diameter, tie spacing, concrete core area, and casting direction of specimens. Test results indicate that the initial tangent modulus and initial Poisson's ratio of the concrete are not affected by confinement. However, confinement enhances both the peak stress and strain at peak stress. Vertically cast confined fiber concrete exhibits larger strain at peak stress and has higher postpeak ductility compared to the corresponding horizontally cast specimen. Vertically cast confined nonfiber concrete also has larger strain at peak stress, but ductility is hardly improved over horizontally cast specimens. Based on test data, an analytical model is proposed to generate the complete stress-strain curves of high-strength concrete confined by lateral ties. The proposed model has been found to agree well with the stress-strain curves generated experimentally.