نسرین بخشایش اقبالی

Reinforced concrete structures tend to deteriorate over time for various reasons, including design errors in buildings and additional loads that were not taken into account when designing the building. Therefore, it is necessary to strengthen the structural elements to increase their endurance for overloads, which is the main purpose of this research. This research includes experimental studies to enhance the flexural and shear strength using jacket with SCC and hybrid reinforcement (Steel and GFRP) bars. The experimental program includes casting and testing nine specimens. It is divided into two steps: the first step includes casting nine specimens of beams using NSC with cross-sectional dimensions of 150 x 250 (width x height) and a total length of 1750 mm. The second step includes strengthening eight specimens by adding a reinforcement layer using Steel, GFRP, and hybrid (Steel and GFRP)bars, then 8 specimens were fixed using U-shape Steel bars on the sides of the control beam by using sikadur-30LP as an adhesive with jacketing and Self-compacting Concrete. These strengthened groups are divided into secondary groups that differ by the thickness as (∆= 50mm, ∆= 75mm). Concrete cover is 25mm and the total depth is (325 and 350mm). One control beam is tested for comparison purposes that is not strengthened and eight strengthened beam are tested, which have different thicknesses. The significant variables examined in the trials are the effect of increasing the value of ∆, which leads to an increase in the effective depth and the GFRP replacement ratio from (0% to 100%). All RC beam specimens are designed according to the ACI Committee (318-2019), and are subject to two-point loads until failure. By increasing the thickness of the strengthened beams by steel, GFRP, and hybrid reinforcement (Steel and GFRP) bars to ∆= 50mm , significant improvements were obtained in the load-carrying capacity of the RC beams from 73.2 to 88.4% relative to control specimens. On the other hand, the load-carrying capacity of the strengthened beams was improved by increasing the thickness (∆= 75mm) using Steel , GFRP, and hybrid reinforcement (steel and GFRP) bars. The experimental results showed significant improvements in the load-carrying capacity of the RC beams from about 80.4 to 102.9% compared to the control specimens.