## 4 Discussion
### Deflection under Sustained Loading
The beams then experienced sudden shear failure at deflections 227%, 262%, and 202% greater than BC1. The application of sustained load increased the deflection at sudden shear failure for beam series I by 28.49 mm (1.122 in.) or about 230% greater than BC1. All beams in series II experienced a sudden shear failure at the peak load. The failure deflections for series II (B10-SL excluded) increased by 230%, 108%, and 122% or by an average of 8.60 mm (0.339 in.) or 150% more than that of BC5. The effect of creep in the concrete under compression during sustained load and possible bond-slip of the tension reinforcement may have allowed for additional deformations to occur before the final shear failure. The increase in deflection at shear failure for both series was significant (190%). In addition, the control experienced sudden shear failure, whereas the sustained specimens experienced significant flexural cracking, which allowed for additional deformation before the shear failure. This may be an indicator of possible structural issues in actual structures. Figure 16: Percent increase in deflection with time beams series I.  
Figure 15: Deflection increases vs. sustained load intensity after 24 days of sustained load. For beam series II, after the sustained load period, the beam's load was increased by 2.5 to 6% and held constant for a time period of 2-3 days. The purpose of the stepped loading was to evaluate the near failure behavior of the beams. However, testing time constraints did not allow for a long period of sustained loading. During these stepped loadings, the beam's deflection increased due to the increase in load and over time during the sustained loading. The rate of deflection increase with time was comparable to the rate at the first stage of sustained loading. B6-SL reached a sustained load of 19.92 kN (4479 lb) (14 th stage) for two days without failure. The beam was then loaded to failure and failed at a load of 21.13 kN (4750 lb). The load level was 8% greater than the BC5's peak load (18.35 kN) (4216 lb) and only 6% greater than the previous loading stage that did not cause failure. B7-SL was subjected to a sustained load (third stage) of 18.16 kN (4084 lb) for two days without failure, which is 3% less than the peak load of the BC5. B7-SL failed during loading the next stage at a load of 18.70 kN (4205 lb) which is only 3% greater that the load level it held for two days in the previous stage. B9-SL was able to resist a sustained load of 18.82 kN (4230 lb) (fourth stage) for two days without failure, which is 0.3% greater than the BC5's peak load. B9-SL failed in the fifth stage of sustained load after 15.83 min at a load of 19.26 kN (4330 lb), which is 5% greater than the peak load of the BC5 but only 2% greater than the previous  
Figure 17: Percent increase in deflection with time beams series II. Figure 18: Percent increase in deflection with time for specimen B10-SL. loading stage. These results indicate that RC shear-controlled beams may have a much greater ability to withstand sustained loads than plain concrete. The rise in peak load in sustained specimens was attributable to random scatter and continuing time curing.