Externally Bonded Reinforcement On Grooves Research Articles

Externally bonded reinforcement in grooves (EBRIG) technique to postpone debonding of FRP sheets in strengthened concrete beams

Recently a new method for flexural strengthening of concrete beams with FRP sheets, named as grooving method (GM) with the special technique of externally bonded reinforcement on grooves (EBROG), has been introduced as alternative to conventional externally bonded reinforcement (EBR). Based on some experimental investigations, the EBROG method can considerably postpone the debonding phenomenon and in some cases may completely eliminate it. The aim of the current study is to introduce and to examine another improved strengthening procedure by using the GM method when the FRP sheets are in direct contact with the internal surfaces of the grooves on the tension face of concrete beam in a wet-lay-up application. This technique is named externally bonded reinforcement in grooves (EBRIG). For this purpose, 32 beam specimens with dimensions of 120×140×1000mm were cast, strengthened with one, two or three layers of FRP sheets and then subjected to four-point flexural loading. Results showed considerable increase in ultimate limits for beams strengthened with EBROG and EBRIG techniques compared to those strengthened with EBR method. The EBRIG technique performed as good as EBROG for one layer of strengthening FRP sheet; however, it permitted for higher failure loads and displacements compared to EBROG method when multiple-layer FRP sheets were used.

Performance of EBROG Method under Multilayer FRP Sheets for Flexural Strengthening of Concrete Beams

Externally Bonded Reinforcement (EBR) is known as a conventional method for flexural strengthening of concrete beams with Fiber Reinforced Polymer (FRP) composites. However, concrete beams strengthened with this method are often associated with premature debonding mechanisms. Recently, a new promising method has been introduced at Isfahan University of Technology (IUT) to postpone or eliminate debonding of FRP sheets from concrete surface in concrete beams strengthened for flexure, named Externally Bonded Reinforcement On Grooves (EBROG). Experiments have shown that the probability of debonding when attached to concrete substrate using EBROG method is much lower than the EBR method; and in some cases debonding is completely eliminated. The aim of the current study is to examine the efficacy of grooving method when used under multilayer FRP sheets. For this purpose, beam specimens with dimension of 120×140×1000mm were cast and strengthened with both conventional surface preparation and EBROG method with different number of layers of FRP composite. Then, the strengthened beams were subjected to a four point flexural loading. The results showed that the EBROG method provides higher failure loads in the beams strengthened with multi FRP layers compare to those with conventional surface preparation.