Strengthening of concrete beams with fasteners and composite material strips-scaling and anchorage issues
Bank, Lawrence C.; Borowicz, David T.; Arora, Dushyant.; Lamanna, Anthony J.; Velázquez, Gerardo I.; Ray, James C.
Technical ReportAbstract: A system to rapidly strengthen concrete beams and slabs, known as the Mechanically-Fastened Fiber-Reinforced Polymer (MF-FRP) system, has been developed. In the fourth year of research on the subject, the focus was on scaling and anchorage issues. The effect of increasing the number of strips, the fastener spacing, termination distances, and the use of expansion anchors at the strip ends were considered. The scaling study also investigated the use of the MF-FRP system on a full-scale highway bridge. A second series of tests was conducted on large-scale T-beams at the U S. Army Engineer Research and Development Center, Vicksburg, MS, in the summer of 2002. The results of this testing and of parametric design studies conducted were used to design the strengthening system for a flat-slab bridge built in 1930 in the city of Edgerton, WI, and slated for replacement in 2003. The bridge was strengthened with the MF-FRP system in the summer of 2002 and tested to failure in the summer of 2003. An investigation was also conducted into the properties of the FRP strips with different constituent material properties. An optimal strip design to produce the best ultimate longitudinal strength and stiffness, as well as bearing strength, bas been recommended to the manufacturer. The research conducted revealed a number of important scaling related issues with the MF-FRP system. It was found that multiple strips were not as effective as single strips, that a double row of fasteners at 2 in. on center is less effective than a single row of fasters at 3 in. on center, and that mechanical anchor bolts at the ends of the strip significantly improved performance and delayed the onset of end- delamination failures. The importance of a small termination distance from the support was confirmed in testing. Fatigue testing to 2 million cycles showed no degradation of the MF-FRP strengthening system. The full-scale bridge application proved the versatility of the system. Strips were easily and rapidly attached to a severely deteriorated concrete soffit that would not have permitted the use of an epoxy-bonded FRP (EB-FRP) strengthening system. Ten (10) months of environmental exposure did not appear to reduce the effectiveness of the system, and no degradation in material properties of the FRP strips was seen. The ultimate failure test on the bridge proved the ability of the MF-FRP system to increase the strength of a reinforced concrete bridge. Analytical models to predict the strengthening were shown to produce reasonable predictions. These models can be used for design purposes.
Geotechnical and Structures Laboratory (U.S.)Engineer Research and Development Center (U.S.)
Beam retrofit Bridge retrofit Beam upgrade Bridge upgrade Bridges Fiber reinforced polymeric FRP FRP plates Mechanical fasteners Concrete beams Fiber-reinforced concrete Fiber reinforced concrete Fatigue Performance Design
ERDC/GSL TR ; 04-5.
Approved for public release; distribution is unlimited.