Impact of fiber-induced tensile strain hardening on the bearing performance of ECC and UHPC pipes: Experimental study and strength modeling

The mechanical and durability performance of concrete pipes is critical in modern infrastructure, particularly in regions with high load demands and stringent maintenance requirements. This study addresses these challenges by exploring the use of tensile strain-hardening cementitious materials—namely, Engineered Cementitious Composites (ECC) and Ultra-High-Performance Concrete (UHPC)—as advanced alternatives to conventional concrete. A total of seven specimens were evaluated under three-edge bearing tests in accordance with ASTM C497 to assess their damage pattern, cracking strength, ultimate strength, stiffness, and energy dissipation capacity. The effects of fiber type, fiber volume fraction, and the presence of a steel cage reinforcement were systematically explored. Experimental results demonstrated that both ECC and UHPC pipes offered significantly enhanced cracking and ultimate strengths. The inclusion of steel fibers in UHPC was particularly effective, allowing pipes with just 0.5% fiber volume to achieve comparable or even superior stiffness and energy dissipation capacities compared to steel-reinforced conventional concrete counterparts. These findings suggest the feasibility of either reducing or completely replacing traditional steel reinforcement with high-performance fiber reinforcement. Furthermore, the study developed and validated analytical models that reasonably predict the cracking and ultimate strengths of the pipes, with an average underestimation of 5% and 7%, respectively.