Structural characterization of UHPC pipes under transverse compression using digital image correlation

Ultra-High Performance Concrete (UHPC) has the potential for thin-walled structural applications, including pipelines subjected to external overburden loads. This pioneering study focused on performance evaluation of UHPC pipes under transverse compression load using digital image correlation (DIC). The parallel plate test method was used in accordance with ASTM Standard D2412–21. The parameters investigated were type of fibers (Polyoxymethylene (POM) and Steel), fiber content by volume (0 %, 1 % and 2.5 %) and internal circumferential steel reinforcement ratio (0 % and 1.07 %). The results showed that steel fibers significantly increased load capacity and stiffness compared to POM fibers. A pipe with 1.5 % steel fibers and no steel mesh reinforcement has an equivalent strength to that reinforced by 1.07 % steel mesh with no fibers. A simple design equation is developed for the strength of UHPC pipes based on a nonlinear finite element model and a parametric study. Half of the UHPC pipes analyzed met the requirements of ASTM C1765 ultimate load classes IV and V as well as AS/NZ 4058 classes 6 and 8. The parametric study demonstrated the effectiveness of UHPC pipes relative to conventional reinforced concrete (RC) pipes. For example, a UHPC pipe with only 1 % steel fibers achieved the same ASTM C76 Class IV rating as an RC pipe of the same inner diameter but with a range of wall thicknesses 63–156 % larger than that of the UHPC pipe. • First study on UHPC application in thin-wall pipes tested using parallel plate test setup and DIC. • Varied fiber dosage (0–2.5 %), type (steel or POM) and internal steel mesh ratio (0 or 1.07 %). • Pipe with 1.5 % steel fibers and no mesh has equivalent strength to one with 1.07 % mesh and no fibers. • Developed a simple design equation for strength based on nonlinear FE model and parametric study. • UHPC pipe with 1 % steel fibers had same ASTM C76 Class IV rating as RC pipes with 63–156 % thicker walls.