Fig. 4

Strength ratio \( \left( {{{f^{\prime}_{cc} } \mathord{\left/ {\vphantom {{f^{\prime}_{cc} } {f^{\prime}_{c} }}} \right. \kern-0pt} {f^{\prime}_{c} }}} \right) \), strain ratio \( \left( {{{\varepsilon_{\text{ccu}} } \mathord{\left/ {\vphantom {{\varepsilon_{\text{ccu}} } {\varepsilon^{\prime}_{\text{c}} }}} \right. \kern-0pt} {\varepsilon^{\prime}_{\text{c}} }}} \right) \), and ductility factor (μ) vs number of strips \( (N_{f} ) \) for the columns in a Group 1, b Group 2, c Group 3, and d Group 4.