Experimentally based parameters applied to concrete damage plasticity model for strain hardening cementitious composite in sandwich pipes

Sandwich pipes (SPs) composed of two concentrically steel tubes with a strain hardening cementitious composite (SHCC) filling core is a new concept designed for oil and gas transportation in deep waters. In this concept, the SHCC core is the most critical component that should withstand the combined loading of high hydrostatic pressure and bending moment. This paper proposes a particular concrete damage plasticity (CDP) model for the SHCC core based both on experimental data and on the continuum damage mechanics theory. The basic fundamentals of the CDP model can be divided into three major issues, namely, damage evolution, yield criterion, and plastic flow rule. For the damage evolution, two models of damage variables, under tension and compression, respectively, were built based on uniaxial experimental data available and the fracture energy theory. For the yield criterion, the parameters for the Lubliner model were fitted according to available experimental data from uniaxial and biaxial compressive tests. For the plastic flow rule, the dilation angle was deduced from the results of triaxial compressive tests combined with the Drucker-Prager type plastic flow rule. Finally, four-point bending tests were carried out on SHCC specimens and collapse tests were conducted on SP models to allow a correlation study between experimental data and results obtained from numerical simulations incorporating the proposed CDP model. The correlation between numerical and experimental results showed good agreement, demonstrating that the proposed CDP model can accurately reproduce the mechanical behavior and damage distribution experienced by an SHCC material.