Flexural behavior of RC continuous beams strengthened with strain hardening cementitious composites

This study investigates the behavior of reinforced concrete (RC) continuous beams externally strengthened with strain-hardening cementitious composites (SHCC) layers. Although other techniques for strengthening continuous RC beams have been studied, limited attention has been given to the use of SHCC in these applications, particularly with discontinuities at the mid- support due to column heads. By addressing these gaps, this research advances the understanding of SHCC applications for retrofitting and provides a more realistic structural solution for strengthening such beams. The experimental program involved flexural testing of five RC continuous beams: one un-strengthened control beam and four strengthened with SHCC layers at the mid-support negative moment region. The strengthening configurations included two beams strengthened with L-shaped SHCC layers and two beams strengthened with U-shaped SHCC layers, extending to either half or full beam height. To overcome discontinuity at the column head, CFRP laminates were added to the L-shaped SHCC configurations. The control beam exhibited an ultimate load of 392 kN, while the strengthened beams exhibited failure loads that ranged from 418 to 496 kN, with the U-shaped configuration showing the highest load capacity of 496 kN, a 27 % increase. Debonding occurred in the L-shaped strengthened beams, while no debonding was observed in the U-shaped beams. A finite-element-based numerical model was developed using ABAQUS and was validated using experimental data. The Concrete Damage Plasticity (CDP) model was used for both concrete and SHCC, and cohesive surface-to-surface interaction was used to model the bond between the concrete and SHCC layers. The model showed good agreement with the experimental results and can be used for further parametric studies. This study concludes that SHCC strengthening is a viable solution for enhancing the flexural capacity of RC continuous beams.