الفهرس | Only 14 pages are availabe for public view |
Abstract The strengthening of existing concrete structures using FRP composites had spread worldwide due to the advantages offered by these composites in comparison with other traditional materials. Basalt fiber reinforced polymer (BFRP) is a newly developed material in this field that is expected to compete strongly among other types of FRP composites. This research aimed at studying the flexural behavior of RC columns strengthened with different techniques using BFRP bars to assess their efficiency for strengthening RC columns in order to be introduced as an alternative to other types of FRP bars. Moreover, this study investigates a new type of strengthening technique named the “hybrid” technique, which is expected to offer lots of advantages owing to combining two well-known techniques, FRP jacketing and NSM techniques. Basalt fibers are inorganic fibers, similar to glass fibers, that are created by melting basalt rocks. The manufacturing process of basalt fibers consumes less energy and does not need any other additives in the single production process, consequently, leading to a low cost of fibers. The initial studies showed that the basalt fibers have high tensile strength and modulus, better chemical resistance, extended operating temperature range, and are considered to be more eco-friendly when compared to E-glass. Furthermore, basalt-FRP has been proven to have advantages in attaining the goal of improving the safety and reliability of structural systems when compared to traditional glass FRP composites. These advantages make basalt fibers a promising alternative to glass fibers as a reinforcing and strengthening material. This study consists of two phases, phase I was aimed at studying the mechanical properties of the basalt FRP bars. In this phase, several tests were conducted on the FRP bars to investigate their mechanical properties to be used later in phase II. Phase II was aimed at investigating the structural performance of RC columns strengthened with different techniques using BFRP bars. The variables considered in this phase are the strengthening effect (unstrengthened and strengthened), the type of the FRP bars (BFRP and GFRP), the strengthening technique (NSM and hybrid), and the diameter of the used FRP bars (10 mm and 12 mm). The test results are discussed and analyzed in terms of cracking, yielding, and ultimate behavior, in addition to the crack pattern and failure modes. The test results showed the efficiency of strengthening RC columns with different techniques using BFRP bars in enhancing the overall flexural behavior. Moreover, the test results demonstrated the significance of using BFRP bars compared to the more traditional GFRP bars for strengthening RC columns. Using the NSM technique in strengthening RC columns can increase improve the ultimate load capacity and the ductility of the columns by 30% and 169%, respectively. Using the hybrid technique can significantly enhance the ultimate load capacity and the ductility of the columns by 95% and 241%, respectively. |