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The Kentucky Transportation Center’s (KTC) research team, in cooperation with the Kentucky Transportation Cabinet and the Federal Highway Administration, recently determined that a product originally intended for aerospace technologies could be used to successfully repair damaged concrete bridges.
The product, QISOTM Braided Triaxial Fabric, is a single layer quasi-isotropic carbon fabric that was developed by A & P Technology (Cincinnati, Ohio). QISOTM drastically improves damage tolerance and energy absorption, and has been applied to jet engine fan cases, aircraft control surfaces, and radio dishes.
Dr. Issam Harik, Manager of the KTC Structures Program at the University of Kentucky, decided to use QISOTM to restore the capacity of a bridge pier in Louisville, Kentucky. The steel reinforcement of the pier was severely rusted in the vertical and transverse directions. The concrete cover also had multiple pieces that had deteriorated and fallen off, which exposed the pier core.
“A single layer of QISOTM Triaxial Fabric can be applied to the bridge pier in place of two orthogonal layers of fabric having unidirectional fibers. This fabric has cut the application time in half, which reduces the repair costs,” said Harik. In October 2012, the QISOTM fabric was also used to repair a concrete bridge located in Simpson County, Kentucky (see picture nearby). This bridge had multiple cracks on several beams near the abutments and at the center pier. Most of the cracks were diagonal, but vertical and horizontal cracks were also identified during inspection. The retrofit required a fabric having multidirectional fibers. Dr. Abheetha Peiris, a research engineer in the Structures Program at KTC, supervised the project that involved KTC staff members completing the repairs. “The QISOTM Braided Triaxial Fabric provided us the unique opportunity to strengthen the deteriorating beams and halt the crack growth in multiple directions by using a single layer of fabric. This carbon fiber fabric is light weight and can be easily applied to the concrete surface,” said Peiris.
KTC was the first to use QISOTM for civil engineering infrastructure purposes. To date, four bridges in Kentucky have been repaired using this technology.
More information: www.ktc.uky.edu