Axial-flexural interaction in square RC columns confined by intermittent CFRP wraps

External reinforcing of concrete elements by CFRP composites is a well-accepted method adopted for strengthening all structural load-bearing members including reinforced concrete (RC) columns. Previous studies have been mostly focused on strengthening RC columns for pure axial-loads, while most RC columns practically function as beam-columns; that is, they are subjected to both axial loads and bending moments simultaneously.It is the objective of the current study to carry out an experimental assessment of the load bearing capacity and ductility of columns externally strengthened with intermittent CFRP wraps when subjected to simultaneous axial loading and bending moment. The assessment is accomplished by comparing intermittently wrapped columns with unconfined ones in terms of their strength and ductility. For this purpose, 10 square RC columns, 133 × 133 mm across and 500 mm in height, were subjected to zero, 30, 60, 90, and 120 mm loading eccentricities. The results of the study showed that, compared to unconfined RC columns, intermittent wrapping of square RC columns with CFRP improved their performance through enhanced load carrying capacity and ductility under eccentric loading.Finally, the P–M (axial loading-bending moment) interaction diagrams were drawn for the strengthened columns. Comparison of the experimental results with those obtained from the expressions suggested in different codes such as ACI 440.2R and fib bulletin 14 showed the conservative estimates of these codes in comparison to experimental measurements.