Stress-strain models for ultra-high performance concrete (UHPC) and ultra-high performance fiber-reinforced concrete (UHPFRC) under triaxial compression

The constitutive behavior of ultra-high performance concrete (UHPC) and ultra-high performance fiber reinforced concrete (UHPFRC) under multiaxial stresses, which has not been well understood, needs to be urgently investigated in order to meet an increasing demand for use of UHPC/UHPFRC in construction. This paper therefore presents an experimental study on the triaxial compressive behavior of UHPC and UHPFRC under triaxial compression. The compressive strengths of UHPC and UHPFRC in present study were up to 126.9 and 151.5 MPa, respectively. The test variables included the level of lateral hydraulic pressure, steel fiber volume fraction, and uniaxial compressive strength of UHPC and UHPFRC. The present experimental study provides the much-needed systematic test data on the triaxial compressive behavior of UHPC/UHPFRC. The test results showed that the lateral hydraulic pressure significantly enhanced both the strength and ductility of UHPC and UHPFRC. The presence of steel fibers had significant effects on the axial stress-axial strain behavior and the dilation behavior of UHPC and UHPFRC. Finally, new axial stress-axial strain models as well as a new equation for the axial strain-lateral strain relationship for UHPC and UHPFRC were first proposed.