Development Of Tensioning And Self-locking System For Pre-stressed Straps Of CFRP

Abstract:As an innovative and prospective scheme, strengthening the reinforced concrete (RC) beam with pre-stressed Carbon Fiber-Reinforced Polymer (CFRP) straps can distinctly increase the strengthening efficiency of the CFRP fabric, which is famous for its high strength-to-weight ratio, excellent corrosion resistance. It can effectively decrease the stress and deformation of the RC members, delay the initial cracking and restrain the development of cracks, thus the resistance and durability of the RC members is able to be enhanced. However, few schemes about tensioning and anchoring pre-stressed CFRP sheets have been reported so far. The existed schemes are generally in need of unhandy device, large working place, and always lacking in introduction of detailed process.In order to improve the reliability and conveniences of the strengthening scheme with pre-stressed CFRP straps, a tensioning and self-locking system has been invented, with theoretical, numerical analysis and experimental study having been conducted. Completed research jobs are mentioned below.1) Theoretical description of the self-lock the CFRP straps achieving at tensioning end and anchoring end in the system and selection of detailed dimensions of the device according to the design requirements.2) The pre-stress is exerted by tightening the nuts on the tensioning screws and the pre-stress level is controlled by the readings of the strain gauges on the screws.3) A complete description of the strengthening process with the mentioned system.4) Selection of the taper angle for the wedge-shaped fixture in accordance with the mechanical performance under design load which is analyzed with the help of finite element method.5) Experimental research. The ultimate load for4layers of CFRP straps fitted in the system was acquired in the tensile test; the non-uniformity of the tensile strain along the horizontal axis in CFRP strap was discovered and defined according to3arch tests of steel beam which is aimed at simulating the practical application and evaluating the efficiency of the designed system.