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

U.S. Transportation Collection2020PDFTech ReportAslan, KShokouhian, MAdegoke, MUpton, GMorgan State University. College of EngineeringPennsylvania State University. Thomas D. Larson Transportation InstituteUnited States. Department of Transportation. Research and Innovative Technology AdministrationUnited States. Department of Transportation. University Transportation Centers (UTC) ProgramPennsylvania State UniversityUnited StatesCarbon fibersColumnsCompressive strengthDeformation curveFiber reinforced polymersFinite element methodRetrofittingBridge designEngineering educationCIAM-COR-R1769A3551847103Final Report 03/01/2019 \u2013 03/01/2020External confinement of concrete columns by means of carbon fiber reinforced polymer (CFRP) wraps has proven to be an efficient technique for structural retrofitting and strengthening. This report presents an experimental investigation that was conducted 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 was carried out to evaluate the remaining strength and stress-strain behavior of partially damaged concrete columns externally retrofitted with CFRP strips. Fourteen cylinder specimens were 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-inch diameter and 16-inch height. The same concrete mix and curing conditions were used throughout the study to achieve 4,000 psi compressive strength in 28 days. All of the test specimens were 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 was achieved.105