Experimental Investigation of Residual Compressive Strength of Partially Confined Concrete Column Retrofitted Using CFRP Wrap

External confinement of concrete columns by means of carbon fiber reinforced polymer (CFRP) wraps have proven to be an efficient technique for structural retrofitting and strengthening. This paper presents experimental investigation to assess the residual compressive strength of CFRP wrapped 1/6-scale concrete columns using strips to enhance confinement while still enabling visual column inspection. The experimental work is carried out to evaluate the remaining strength and stress-strain behavior of partially damaged concrete columns externally retrofitted with CFRP strips. Fourteen (14) cylinder specimens are constructed, instrumented, and tested in seven groups, including fully double-layer vertically and horizontally wrapped, partially wrapped with 2-strip, partially wrapped with 3-strip, fully single-layer vertically and horizontally wrapped, and unwrapped concrete column specimens with 4 in. diameter and 16 in. height. The same concrete mix and curing conditions are used throughout the study to achieve 4,000 psi compressive strength in 28 days. All test specimens are subjected to monotonic uniaxial compression loads in two steps: (1) before retrofitting and loading up to 70% of failure point, and (2) after retrofitting and loading up to failure. Several parameters that influence confinement effectiveness of CFRP and increase the residual compressive strength of retrofitted column were evaluated including the number of CFRP composite layers and fiber orientations with respect to the circumferential direction. A finite element model was developed using ANSYS 19.2 to compare with the test results, and a close agreement achieved.