## 3 Discussion of Results
### Positive Bending Behavior Post-Repair  
One of the three repaired girders for each material was tested in positive bending identically to the crack-inducing loading regime to assess how the added repairs would improve performance. The load vs. deflection curves for each of the post-repair tests are shown in Figure 7 and the strain readings from the reinforcing in the deck and in the repair are shown in Figures 8-10.  
\begin{table}
\begin{tabular}{c c c} \hline \hline  & **Compressive Strength (MPa)** & **Coefficient of Variation** \\ \hline Class AA & 34.9 & 3.3\% \\ UHPC & 139.5 & 3.3\% \\ FRSCC & 48.7 & 15.0\% \\ MALP & 30.6 & 1.7\% \\ \hline \hline \end{tabular}
\end{table}
Table 2: Concrete compressive strengths at 28 days.  
Figure 6: Example crack patterns in the connected girder specimens when subjected to positive moment bending.  
Figure 8: 1-UHPC load vs. strain for each instrumented reinforcing bar.  
Figure 7: Load vs. deflection plots for all repairs subjected to positive bending.  
Figure 9: 1-FRSCC load vs. strain for each instrumented reinforcing bar.  
The girder joint repairs using the UHPC and FRSCC re-established load carrying capacity beyond the original failure load. Both repaired girders exhibited near-identical responses up to the point of the average pre-repair cracking load. This included a linear response up to a yielding load, where the stiffness was reduced (see Figure 7). The overall behavior appears to mimic the conventional reinforced beam bending response, except there is no low-load stiffness change caused by crack initiation in a pristine beam. This could be due to the pre-cracked nature of the repaired specimen and the fiber reinforcement of both repair materials precluding the formation of large, traditional flexural cracks. Conversely, the MALP repair exhibited a softening behavior and did not reach the pre-repair cracking load (see Figure 7). The better stiffness response appears to indicate load transfer to the UHPC and FRSCC repairs. However, the low strain values in the repair reinforcing bars implies that the additional load carrying capacity was mostly developed by the fibers in the repair materials. This would explain why the UHPC reached a higher peak load than the FRSCC, since the UHPC uses steel fibers, compared to polypropylene fibers in the FRSCC, providing both higher bending strength and ductility for the UHPC.  
Lack of load transfer to the MALP repair is also indicated in the strain readings. The deck reinforcing steel located in the top of the girder was in tension through the entire test of the MALP specimen. This indicates that there was little to no load transfer to the MALP repair. Conversely, the UHPC and FRSCC deck reinforcing steel was in compression up to near the failure load. For both UHPC and FRSCC, the deck reinforcing reached an apex compression strain at approximately the same load as when the load vs. deflection curve exhibited signs of softening behavior. This load indicates the point at which the repair material lost stiffness by either localized damage in the repair material or loss of bond to the damaged substrate. The fact that the UHPC had a higher peak load than the FRSCC appears to indicate that this softening was more a function of localized damage in the repair material due to the higher strength of the UHPC. In addition, no cracks were observed on the longitudinal face of either the UHPC or the FRSCC repairs. After the loss of stiffness and as the underlying flexural cracks formed higher up in the continuity joint, the neutral axis was gradually shifted up as the load increased until it was above the deck reinforcing, producing tensile strains in the steel.