INVESTIGATION OF NOVEL ANCHORING DEVICES FOR OPEN HOOP CFRP STRIPS BONDED ON R/C ELEMENTS UNDER MONOTONIC AND CYCLIC LOADING-UNLOADING CONDITIONS

Abstract eng:
Results obtained from research conducted in the framework of an initiative introduced by the Hellenic Earthquake Planning and Protection Organization aiming to support relevant provisions of the Greek Code for the repair and strengthening of R/C structures are presented and discussed. When trying to utilize fiber polymer sheets, as external reinforcement attached on R/C elements, their potential of high tensile strength is prevented by the FRP sheets’ debonding mode of failure thus limiting the exploitation of the material. In order to confront this limitation the effectiveness of two novel types of anchoring devices that can be incorporated together with such FRP strips was studied. For this purpose special unit beam concrete specimens were fabricated and were used to attach the open hoop carbon strips (CFRP). The novel loading arrangement developed at Laboratory of Strength of Materials and Structures was utilized to apply the necessary forces to these unit beam specimens together with instrumentation capable of capturing the behavior of these specimens up to failure. Studying in this way the transfer of forces from the open hoop FRP strips it could be demonstrated that when this type of retrofitting was accompanied with a properly designed anchoring device, a significant increase in the bearing capacity of the tested specimens was observed. The present investigation incorporates also the influence of number of cycles, in a loading-unloading way, on the overall behavior of the strengthening scheme, in terms of ultimate strength and observed mode of failure. Finally, this paper includes the most important findings of a supplementary numerical investigation, using the FEA software ABAQUS, aimed to study the behaviour of the novel anchoring device which is patented in Europe under the patent number WO2011073696.

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