Compressive behaviour of RC walls strengthened horizontally with near-surface-mounted closed stirrups and externally bonded stainless steel strips

Traditionally, reinforced concrete (RC) walls are often designed as shear walls to provide lateral resistance. However, RC walls can be designed as load-carrying members to replace closely spaced edge columns in low- to mid-rise buildings. Often, in order to facilitate utilisation of services, openings are made in these walls, which may significantly impact their load-bearing capacity and thus will require strengthening. In this study, RC walls with and without openings were strengthened using near-surface-mounted (NSM) steel bars and confined with stainless steel (SS) strips as externally bonded reinforcement (EBR) in an attempt to enhance their vertical load-bearing capacity. A series of tests was carried out to study the effects of the presence of openings, strengthening technique (NSM reinforcement and EBR), the materials used for strengthening (steel bars and SS strips) and the ratio of additional reinforcement. The results showed that the proposed strengthening method can enhance the ultimate load of RC walls without openings, by 18–35%. In addition, although introducing an opening in RC walls reduces their ultimate load significantly, the proposed strengthening method was found to enhance their ultimate load. Linear and non-linear three-dimensional finite-element models (FEMs) were developed to simulate the performance of the tested specimens and the models were validated by comparing their results with the experimental observations. The validated FEMs were then employed to carry out a parametric study.