Assessment On External Post Tensioning To Strengthen Reinforced Concrete T-Beam

Abstract

External posttensioning was become one of the most attractive techniques for strengthening reinforced concrete structures and the technique is widely used in the construction of various engineering structures and also as one of the most efficient approaches for strengthening of both new and existing structures. In an external prestressing system, the prestressing tendons are placed outside the concrete section and the prestressing force is transferred to concrete through end anchorages. This research is carried out to investigate the externally post-tensioning technique for strengthening RC T-beams. In this research, ten identical T-section RC beams having the same dimensions and material properties were modeled and analyzed based on nonlinear finite element method applying two mid-third concentrated loads by using Abaqus software was investigated by varying the independent variables up to failure. Nine of these beams are strengthened by using external tendons, while the remaining beam is kept without strengthening as a control beam. Two external strands of 12mm diameter were fixed at each side of the web of the strengthened beams and located at depth of 200mm, 225mm and 243mm from top fiber of the section (dps). So that the depth of strands to overall depth of the section ratio (dps /h=0.8), (dps /h=0.9) and (dps /h=0.972) were used in this research thesis. Eccentricity and strengthened length has significant effect on external post tensioning to strengthen of reinforced concrete beam, as depth of tendons increases and the distance of tendons from beam face decreases, the ultimate load carrying capacity of the beam increases. The load carrying capacity of beam increases as the depth of strand increases. It is concluded that the load carrying capacity for depth of strand 0.8h, 0.9h and 0.972h and strengthened length ratio of 0.83L,0.667L and 0.5L are 40.75%, 51.12% and 62.44% respectively compared to the control beam. The parameter studied was carried out by considering concrete compressive strength, span to strengthened length ratio, depth of strand (eccentricity) and distance of strand from the face of the concrete beam(horizontal eccentricity).