Seismic performance improvement of low-strength RC shear wall strengthened using engineered cementitious composites with steel mesh

Engineered cementitious composites (ECC), with its high ductility and tensile strain-hardening behavior, provides an effective solution for seismic retrofitting. This study investigated the seismic performance and failure mode of full-scale low-strength reinforced concrete (RC) shear walls strengthened by ECC. Cyclic loading test was conducted to evaluate the structural performance in terms of failure modes, hysteretic behavior, skeleton curves, ductility, stiffness degradation, and energy dissipation capacity. The test results showed that two ECC strengthening schemes modified the failure mode and improved ductility of low-strength RC shear walls by forming more and finer distributed cracks, mitigating brittle failure. Compared to strengthening detail using 30 mm ECC alone, strengthening detail using 50 mm ECC with steel mesh reinforcement improved the load-carrying capacity and deformation capacity by 15% and 41%, respectively, addressing the delamination issue commonly observed in single ECC applications. Meanwhile, the further enhanced confinement effect improved the load resistance of the wall, which could maintain stable seismic performance even under large deformations. A parametric analysis demonstrated that the proposed strengthening method exhibited broad applicability for shear walls with concrete grades ranging from C20 to C40. Further, with a strengthening layer thickness of 30 mm, an aspect ratio of 2.5, and a longitudinal reinforcement ratio of approximately 0.346%, the strengthened wall achieved a recommended range that balances performance gains against diminishing marginal returns within the studied parameter space with the range of parameter study. Theoretical models for the flexural and shear strength of ECC strengthened shear walls were also derived and showed good agreement with the test results, verifying the reliability of the design method. This study provides experimental evidence and theoretical support for the engineering application of ECC in the seismic retrofitting of low-grade RC shear wall structures.