Constitutive relationship of ultrahigh performance concrete under uni-axial compression

To investigate the constitutive relationship of ultrahigh performance concrete (UHPC) under uni-axial compression, the similarity and the difference of different constitutive equations of UHPC proposed by available literatures are analyzed and compared. The unified constitutive equation of UHPC under uni-axial compression is suggested. The empirical formulas for calculating the peak compressive strain and the elasticity modulus are obtained by fitting the experimental data of UHPC under uni-axial compression. Finally, the calculation formula for the parameters of the stress-strain curve in the ascending phase of UHPC under uni-axial compression is proposed. The research results show that the constitutive equation provided by the Code for Design of Concrete Structures (GB 50010-2010) can be used to calculate the stress-strain relationship of UHPC. When the axial compressive strength is 80 to 150 MPa, the peak compressive strains of the cylinder specimens are 5.0×10-4 to 7.5×10-4 larger than those of the prism specimens with the same axial compressive strengths. The higher the axial compressive strength is, the larger the difference of the peak compressive strains between the cylinder and the prism specimens. The proposed empirical formulas for the peak compressive strain, the elasticity modulus and the parameter of stress-strain curve in the ascending phase of UHPC have high accuracy and reliability, and can be used for engineering design of UHPC structures. © 2017, Editorial Department of Journal of Southeast University. All right reserved.