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).
