الفهرس 
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Abstract
In this research work, T-sectioned, bonded, post-tensioned (PT) concrete girders which are deficient in shear were strengthened with CFRP sheets using an externally bonded strengthening technique.
Using nonlinear Finite-Element-Method (FEM), three-dimensional models of shear strengthened reinforced concrete beam and PT concrete girder were built for validation of the used software tool Abaqus CAE outputs, and results were verified with the experimental work that found in literature. (Chapter III)
A parametric study was carried out to investigate and analyze: 1) the efficiency of using EB CFRP strengthening system on shear capacity; 2) the effect of CFRP’ orientation angle configuration on shear contribution; 3) the effect of laminates’ different configuration scheme on shear contribution; 4) the effect of CFRP strip width; 5) the continuity of CFRP laminates (either strips or sheets); 6) number of plies; 7) CFRP rigidity (strip-width to strip-spacing ratio); 8) validation of codes’ analytical models. (Chapter IV)
5.2 Conclusion
Based on the analysis results, several conclusions were obtained as follows:
1) The different CFRP shear strengthened girders have exhibited an improvement in ultimate shear capacity with respect to the control girder ranging from 7% up to 18%.
2) The efficiency of the used strengthening systems ranged from 7% for the test specimen (PT-(C)0.45R) with the highest rigidity used (0.45 GPa) up to 21% for the test specimen (PT-(IU)0.14R) with the inclined U-jacket configuration scheme.
3) Using inclined strips with 45⁰ configuration angle, showed a better performance in ultimate shear force combined with a ductile manner than straight strips with 90⁰ configuration angle.
4) Using laminates with U-jacket configuration scheme exhibited a higher contribution in ultimate shear force than externally bonded sided strips only, although using same rigidity and (Wf/Sf) of CFRP strengthening material led to a rapprochement in the ultimate shear force.
5) The test specimen that had the narrowest width exhibited the highest strain value which had led to an obvious increase in the ultimate shear force.
6) Despite the higher CFRP strain induced by the discontinuous laminates, the continuous sheets exhibited a higher contribution in ultimate shear force.
7) The test specimen with the double CFRP plies exhibited a huge decrease in the induced CFRP strain by almost 46% compared with the single ply test specimen showing the lowest CFRP efficiency of all test specimens.
8) The relation between the axial rigidity of CFRP and its contribution of shear capacity is positively proportional with each other up to 0.35 GPa axial rigidity, after that rigidity value the relation tends to be negative.
9) The analytical model presented by the ACI440-2R code agreed with the findings, except for the technique of using no. of plies. On the other hand, the TR55 code was very conservative while the fib code was unsafe to use.
5.3 Suggestions for future work
The research work presented in this thesis dealt with the three-dimensional models using nonlinear FEM, but there is a need for a scaled experimental work to expand knowledge for shear strengthening the bonded PT concrete girders using externally bonded techniques, and set proper hypotheses to be used as a base for new accurate guidelines.