## 4 Conclusions  
In order to examine the effect of the tendon profile's layout on the flexural strength of unbonded prestress concrete bridge I-girders, an experimental investigation was conducted on ten unbonded prestress concrete bridge I-girders with different tendon profile layouts. The following conclusions were drawn from this study:  
1. The flexural destruction of unbonded prestressed concrete bridge I-girders experienced elastic, elastic-plastic, and ductility (plastic) stages similar to those of bonded prestressed concrete bridge I-girders. However, unbonded prestressed concrete bridge I-girders present superior ductility and deformation-recovery ability after unloading. 2. The tendon profile layout has a significant influence on the destruction process in unbonded prestress concrete bridge I-girders. 3. The experimental results showed that the flexural behavior of the tested specimens is divided into three stages: the elastic stage, the elastic-plastic stage, and the plastic (ductility) stage. All specimens exhibited flexural failure. 4. The ultimate load of the specimens using a trapezoidal tendon profile showed a maximum increase of 28.02 kN with an increasing rate of 7.81% for specimen GF-3 TR if we compare it to the control beam. 5. The ultimate load of the specimens using a parabolic tendon profile had a maximum increased load of 49.6 kN with an increasing rate of 13.83% for specimen GF-6 PR if we compare it to the control beam. 6. The ultimate load of the specimens using a harped tendon profile had a maximum increased load of 75.3 kN with an increasing rate of 20.99% for specimen GF-2 HA if we compare it to the control beam. 7. For the specimens using a trapezoidal tendon profile, specimen GF-3 TR had a minimum vertical deflection of 32.36 mm, which was less than the control beam by 4.44 mm, with a decreasing rate of 12.07% from the control beam. 8. For specimens with a parabolic tendon profile, specimen GF-5 PR had a minimum vertical deflection of 35.22 mm, which was lower than the control beam by 1.58 mm, with a decreasing rate of 4.29% from the control beam. 9. For the specimens with a harped tendon profile, specimen GF-2 HA had a minimum vertical deflection of 35 mm, which was less than the control beam by 1.80 mm, with a decreasing rate of 4.89% from the control beam. 10. Each tendon profile shape (trapezoidal, parabolic, harped) with eccentricity at the end (\(\mathbf{e_{e}}\)) = 0 had a maximum ultimate load capacity. It can be concluded that specimen GF-2 HA with a harped tendon profile had the maximum ultimate load capacity compared to all other specimens. Also, it can be concluded that specimen GF-3 TR with a trapezoidal tendon profile had minimum deflection compared to all other specimens, which agrees with the results of the finite element analysis by Ansys 14.0 and Sap2000 version 14 software, completed by [PERSON] and [PERSON] [27,28], and it has the highest (\(\mathrm{P_{cr}}\)/\(\mathrm{P_{u}}\)) ratio compared to all other specimens. These enhancements in specimen stiffness, ultimate load capacities, and deflections are because of the effect of the tendon profile layout on the flexural capacity of girders. 11. The experimental results of the tests on girders with optimized tendon profiles illustrated remarkable improvements in performance. These girders carried higher loads with less deflection than the control beam. The efficiency of prestressing forces throughout the girder length makes the girders with optimized tendon configurations more performant. These improvements allow for a more even distribution of the induced stresses to the concrete member, engaging with more of the cross-section for load carrying. This uniform stress distribution enhances the ductility of the girder and, hence, the service life of the structure. Finally, the research results demonstrate that optimized tendon arrangements achieve substantial improvements in load-carrying capacity, deflection control, and overall performance.