Püskürtme bazalt tekstil takviyeli gfrc ile düşük dayanımlı kolonların güçlendirmesi

Many existing reinforced concrete structures suffer from effects of earthquakes due to low strength concrete and inadequate transverse reinforcement, which affect strength and ductility characteristics of structural elements adversely during earthquakes. One method to improve these characteristics is the external confinement of these elements. Different materials can be used for the purpose of external confinement. Nowadays FRPs (fiber-reinforced polymers) are popular for external confinement due to their advantages such as corrosion resistance, high strength to weight ratio, easy and prompt application and minimal geometry change after retrofitting. On the other hand, using FRPs have some drawbacks as well such as poor behavior of epoxy resins at temperatures above the glass transition temperature, high initial investment cost, difficulty of application of FRP on wet surfaces or low temperatures, incompatibility of epoxy resins and substrate materials, and emission of harmful gases during application. The main objective of this study is to investigate the effectiveness of two external jacketing materials, GFRC (glass fiber reinforced concrete) and textile-reinforced GFRC. Into best knowledge of authors, GFRC have not been used for the external confinement of concrete before. Furthermore, another originality of investigation is the use of spraying technique during application of external jacketing this technique allows application of retrofitting in difficult and narrow areas as well as being much more rapid with respected to other techniques of jacketing. In this study, effects of several parameters, which are effective on the behavior, such as type of jacket material (GFRC or textile-reinforced GFRC), cross-section shape (circular, square or rectangular), and number of basalt layers in textile reinforced jackets (varies from one to three layers) are examined with focus on failure mechanisms of different jackets. The contribution of this retrofitting technique is investigated on short columns experimentally under axial loads while member level theoretical analysis are carried out for the cases of axial loads as well as combined actions of axial loads and flexural moments. In this experimental study totally 26 low-strength (concrete compression strength less than 10 MPa) short columns with four different cross-section type were tested. Spans with circular section with 200 mm diameter, with square cross-section of 200x200 mm, with rectangular cross-section of 200x300 mm and with 200x400 mm, are included in testing program. The heights of all specimens were 500 mm. All specimens were tested under concentric monotonic compression load using Amsler universal testing machine with the capacity of 5000 kN. Additionally, 24 tensile test specimens representing each external jacketing type were also constructed and tested. The data from tensile tests were used in analytical study, and the investigation of tensile behavior for external jacketing. Experimental results showed that external confinement with glass fiber concrete provided a significant increase in axial compressive strength, while basalt textile was effective on enhancement of deformation capability in particular. In the analytical part of the study; firstly, a method was established for estimation of ultimate strength and deformation capacity of concrete members retrofitted with the proposed method. Then, the prediction of the analytical approach possessed are compared with the result of similar tests in the literature. In the second part of the analytical study, the nonlinear flexural behavior of reinforced concrete columns retrofitted with the proposed retrofitting technique are studied by relying use of moment-curvature analysis through fiber analysis approach and relying use of proposed strength and deformation characteristics of reinforced concrete members retrofitted with the proposed method. Finally, in the third part of the analytical study, other models originally proposed for the concrete members externally jacketed with textile-reinforced mortar are used for prediction of tested specimens and obtained analytical results are compared with experimental founding.