The post-tensioned (PT) reinforced beams can provide a fast construction advantage through precast and cast-in-situ structural elements. However, due to the excessive increase in load capacity, especially when it comes to girder of bridges, the strengthening using Fiber-reinforced polymer (FRP) might be a solution. Near-surface mounted (NSM) is one of the methods used in strengthening cases, especially in the case of non-degraded concrete cover. Furthermore, very few researchers visited this area experimentally, which consider cost-effective. In this paper, two finite element models using the Abaqus program validated experimental results for both Post-tension beam and strengthening of the beam using NSM separately as preliminary models for combining both systems. PT reinforced concrete beam subjected to four-point bending loading as well as reinforced concrete beam strengthened with NSM using FRP bars subjected to two-point bending loading examined and validated through a 3D non-linear finite element (FE) model to be compared by the experimental results. This FE model considered the non-linear constitutive properties of concrete, yielding of steel, and the bond between strand, concrete, and FRP bars at NSM. The models were targeting the strengthening of existing Post tension girder beams of existing bridges structures. These modeling results showed a reasonable agreement with the tested beam results in terms of failure modes, the load capacity, load-deflection curve, and cracking behavior.

The applications of post tensioned concrete have increased and have now been used in different regions of the world. There are only few studies which have studied the behavior of retrofitted prestressed concrete experimentally, with the major part of the studies focusing on retrofitted reinforced concrete. This research study is initiated by a desire to more fully investigate the response of it. This paper presents a parametric study established on a beam with T-sec with web width 700 mm and a height of 1800mm, the thickness of the flange is 150 mm, the width of beam flange is 1500mm with span 29.6m. The beam was simply supported and loaded uniformly. A total no. of 20 finite element 3D models was generated taking the all possible failure modes such as FRP rupture, concrete cover separation and concrete crushing in order to study percentage of prestressing steel (Wp) parameter. Finally, a comparison is done between ACI 440.2R-08 code and the finite element results for the ultimate failure load and the predicted failure mode 0