Shear strength of surrounding columns in URM-infilled RC frames retrofitted using the thick hybrid wall technique

This study investigated the shear strengthening effect of the thick hybrid wall (THW) technique as a seismic retrofit approach for unreinforced masonry (URM) wall-infilled reinforced concrete (RC) frames. The THW is a strength–ductility-type seismic retrofit technique developed for pilotis-type RC buildings. The shear strength and failure mechanisms of URM-infilled RC frames retrofitted using the THW technique (also referred as the intended frames) were investigated experimentally and theoretically. Cyclic loading tests were conducted under the influence of a constant axial force on four retrofitted specimens. A shear transition mechanism was developed to measure the shear strength . Moreover, the interaction of the axial force with shear and flexural strengths was defined to provide a comprehensive understanding of the influence of the axial force on the shear and flexural strengths. This interaction measures the shear and flexural strengths, and it simultaneously predicts the failure modes of the intended frames under the influence of axial-force variations. The accuracy of the developed models was examined experimentally. The results demonstrate that the THW technique improves the shear strength of the intended frames considerably. The defined interaction measures both the shear and flexural strengths, and it is able to predict the failure modes of the intended frames under the influence of axial-force variations. In addition, the experimental results confirm the accuracy of the proposed analytical models. The findings of this study are expected to facilitate the application of the THW technique on the intended frames. • An experimental investigation was carried out on four retrofitted specimens. • Shear strength and failure modes of retrofitted URM-infilled RC frames were investigated. • The shear resistance in the form of arch mechanism was developed. • The interaction of axial force with shear and flexural strengths was defined. • The accuracy of the developed analytical models was examined using the test results.