# An Assessment of the Structural Performance of
## 3 Test Results and Discussion
### Test Results under Cyclic Load  
The structural capacity test results of the RC beam specimens under cyclic loading, according to the corrosion rate of the rebar, are shown in Figure 10. Similar to the test results under a monotonic load, as the corrosion rate of the rebar increased, the structural capacity of the beam specimens tended to decrease. In the case of the entire corrosion area, in specimens A-1-2 and A-2-2, Table 4 shows that the average weight loss was nearly identical--about 10.6%--while the yield load and maximum load were reduced to 14.7% and 5.7%, respectively. In specimen A-3-2, it was observed that the yield load and ultimate load reduction were significant, at 69.6% and 60.9%, respectively, with an average corrosion rate of 33.1%. Figure 9: Distribution of cracks for each specimen under monotonic load. For localized corrosion in the constant moment area, as the average weight loss increased from 10.5% (specimen B-1-2), 14.2% (specimen B-2-2), and 21.5% (specimen B-3-2), the reduction in the yield load and ultimate load was 7.6%, 17.9%, and 34.8%, and 0.0%, 8.1%, and 26.0%, respectively, as tabulated in Table 4. Over the average of a 20% weight loss, specimen B-3-2 exhibited a considerable deterioration in structural performance. For localized corrosion in the constant shear area, the reduction in the structural capacity was not as significant as with the other cases. Under a cyclic load, the yield load and maximum load of the RC beam specimens, considering the corrosion of the rebar, are presented in Figure 11. Compared to the test results under a monotonic loading condition, as shown in Figure 8, the structural capacity in terms of the yield strength and ultimate strength decreased with a more pronounced tendency for each corrosion case as the corrosion rate increased. Excluding the deviated  
Figure 10: Deflection of beam versus applied cyclic load. (**a**) corrosion in entire area; (**b**) partial corrosion in mid area; (**c**) partial corrosion in end area. data in Figure 11 (9.35 tons at an average of 14.75% corrosion weight loss, denoted as the solid rectangular symbol), the reduction in the load-carrying capacity due to the average corrosion rates of up to 10% shows a similar trend. However, beyond this corrosion rate, a significant deterioration in the load-carrying capacity was observed especially in the entire area and localized moment area. Over a certain threshold of corrosion, the capacity definitely drops, and cyclic loading worsens this condition. The relationship between the bond strength (shear stiffness) and the level of corrosion of the reinforcements was suggested in a previous paper [41]. The bond strength decreased considerably due to the slippage between the rebar and the concrete under the tensile region, over a certain threshold of corrosion. This may cause premature failures in the case of cyclic loading [72]. Figure 12 presents the localized average weight loss rates of the tensile reinforcement and stirrups in the cyclic loading conditions after corrosion. Similar to the monotonic load cases, it was observed that an increase in the average corrosion rate of the reinforcements resulted in a significant decrease in the load-carrying capacity of the beam specimens. In the case of the rebar corrosion of the entire area, similar corrosion loss results were obtained from specimens A-1-2 and A-2-2. At a corrosion rate of approximately 10.6% in those specimens, the average ultimate strength was decreased to 5.7%. It is clearly shown from the test values of specimen A-3-2 in Figure 12 that the average corrosion rate fluctuates based on the location. In addition, about 33% of the average corrosion rate caused a 69.6% drop in the yield strength and a 60.9% drop in the ultimate strength. In the case of localized corrosion in the constant moment area, a gradual increase in the average corrosion rate in the order of B-3-2 > B-2-2 > B-1-2 led to corresponding strength reductions.