In the months of August and September, a study conducted at the University of Nevada, Reno (UNR) tested three circular columns based on three separate Caltrans designs to analyze the effectiveness of Carbon Fiber Reinforced Polymer (CFRP) wrapping for emergency repair. The main objective of the test was to achieve the highest repairable damage to the columns with no bar rupture and then to successfully conduct an emergency repair on the columns within 48 hours using CFRP. The columns were tested at UNR’s shake table, simulating the Sylmar Earthquake with gradually increasing peak ground accelerations. The extent of the damage to the columns before the repair included visible spiral bars as well as longitudinal bars, buckling in some of the longitudinal bars, cracks in the edge of concrete core and shear cracks at the base of the columns. No bars were ruptured but the columns did approach near failure. Following the earthquake simulation, the repairs began using the Tyfo® SCH-41 Fiberwrap® System. Concrete cracks were pressure-injected with epoxy one day, wrapped with CFRP the following day, and then allowed to cure for 48 hours. During the first 24 hours, the column was subjected to accelerated curing conditions, using heaters to raise the temperature to 110°F with 15% relative humidity. The columns were then allowed to cure at ambient temperature for the following 24 hours. Fibrwrap Construction personnel assisted the university with the required around-the-clock repairs.
After the 48-hour cure time, the repaired columns were re-tested with the Sylmar Earthquake simulation. The repaired columns experienced both increased ductility and strength, and were able to withstand higher peak ground accelerations while maintaining structural integrity. Overall, testing was very successful and results indicated that the Tyfo® Advanced Composite System was a reliable form of column repair for emergency situations.
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