| Title |
Behavior and Acoustic Emission (AE) Activities Characteristics of Reinforced Concrete Beams Strengthened in Shear with Carbon Fiber-Reinforced Polymer(CFRP) Plate Exposed to Freezing and Thawing Cycles |
| Authors |
Yun Hyun-Do ; Kim Sun-Woo ; Lee Young-Oh ; Jeon Soo-Man ; Seo Soo-Yeon ; Choi Ki-Bong |
| Keywords |
Freezing-and-thawing ; Carbon Fiber-reinforced Polymer ; Reinforced Concrete Beams ; Shear Strengthening ; Durability |
| Abstract |
External plating of reinforced concrete (RC) structures with carbon fiber-reinforced polymer (CFRP) plate, sheets, or both, is now a widely recognized as repair and retrofit technique. CFRP sheets and plates are being used to strengthen outside concrete structures. The CFRP reinforcements are bonded to beams and slabs using structural adhesives. Adhesive strength can be affected by environmental exposure. During freezing-and-thawing cycling, temperature-induced stresses in the adhesive layer, due to differential thermal expansion between the CFRP and the substrate concrete, may lead to bond damage and contribute to or cause premature CFRP composite separation. This paper presents the results of experimental program undertaken to investigate the effects of freeze-thaw cycling (from -18 to 4℃) on the behavior and failure characteristics of RC beams strengthened in shear with CFRP plate using acoustic emission (AE) technique. The beams were plated with CFRP plate (S system, thickness of 1.2 mm, tensile strength of 2,800 MPa) then were subjected to between 0 and 400 freezing-and-thawing cycles. Based on the results presented, freezing-and-thawing cycling between 0 and 120 cycles does not appear to significantly affect the overall load deflection behavior, the crack development, and strain distributions of RC beams strengthened in shear with CFRP plate. But CFRP-strengthened concrete beams exposed to more than 240 freezing-and-thawing cycles exhibited 10% reduction in strength compared to CFRP-strengthened RC beam without being exposed to freezing-and-thawing. The AE-b value derived from the frequency-amplitude distribution of AE signals, was compared with the development of fracture process of CFRP-strengthened RC beams. |