Effects Of A Debonding Flaw Size And Location On The Flexural Performance Of CFRP Retrofitted Steel Sections

In US there are several thousand steel bridges at present. Out of them many bridges are at various level of advance deteriorations due to many years of service life and environmental factors. These bridges cannot be fully replaced so retrofitting is the best choice .Earlier steel plates were used. With introduction of FRP in 1960.It is replacing the steel plates as they are lighter in weight and can be made stronger than steel. While installation of these FRP some kinds of Flaws are encountered. The variation of strength of carbon fiber reinforced laminate used for structural repair or strengthening containing a flaw is a major concern due to the potential occurrence of strength reduction. This study investigates the variation in flexural strength, flexural stiffness and flexural deflections of carbon fiber laminate bonded to steel due to the presence of surface flaws in the laminate. To understand this behavior, a series of three point bending tests were performed on a steel I-section which was bonded on FRP laminate containing a flaw. The flaw was the percentage of the un-bonded area of laminate. Fifteen three point static tests were conducted on an American Standard (AISC) section S6X12.5 of 36 grade steel. The variables used in the study were two conditions of steel i.e. un-notched section, and a notched section, produced by cutting a 4inch (102mm) notch. The test setup consisted of the 36 grade S6X12.5 steel beam, 400kip (181.4mt) Tinius Olsen compression testing machine, carbon fiber laminate, epoxy, strain gauges and three strain indicators. Based on test results, it was shown that with 6% or lesser flaw for notched beam was critical flaw size.