Structural Strengthening with Prestressed CFRP Strips with Gradient Anchorage

Julien Michels, Jose Sena-Cruz, Christoph Czaderski, Masoud Motavalli
2013 Journal of composites for construction  
5 This paper presents the principle and the application of an innovative anchorage 6 technique for prestressed carbon-fiber reinforced polymer (CFRP) strips in struc-7 tural strengthening. Additionally, large-scale static loading tests of retrofitted con-8 crete beams are shown. The gradient anchorage, based on the adhesive's ability 9 to undergo accelerated curing at high temperatures, consists of a purely concrete-10 adhesive-strip connection without any mechanical devices such as bolts or
more » ... tes. In 11 a first step, this study summarizes anchorage techniques presented in the literature 12 Manuscript and introduces the basic principles of the new method as well as the necessary com-13 ponents. In a second step, an application on a full-scale RC beam is explained in 14 detail. A commercially available CFRP strip is prestressed up to 0.6 % prestrain and 15 subsequently anchored by sequential epoxy-curing and force-releasing steps at both 16 strip ends. Furthermore, uniaxial tensile tests on the epoxy adhesive and the CFRP 17 strip are used for material characterization and to demonstrate the reinforcing mate-18 rials' integrity after the heating process. It appeared that prestress losses during the 19 anchoring phase are negligible. Furthermore, the method allows a much faster instal-20 lation compared to conventional mechanical techniques and increases durability as 21 no permanent steel elements are necessary. The material tests indicate no damage in 22 the reinforcing CFRP strip as well as a sufficiently fast strength development of the 23 adhesive after accelerated curing. Static loading tests on strengthened large-scale RC 24 beams are presented and show the efficiency of a prestressed CFRP strip with gradi-25 ent anchorage as a retrofitting technique. Finally, first long-term measurements over 26 13 years on a prestressed strip bonded to a concrete plate revealed small prestrain 27 losses. 28
doi:10.1061/(asce)cc.1943-5614.0000372 fatcat:jzchz4gbfvbcxbvqfaysahhjoe