## 3 Results and Discussion  
### General Observations and Failure Modes  
#### 3.1.1 BMRC1, NEWRC 1-5 Columns  
The failure mode and crack pattern of all the column specimens are illustrated in Figure 5. As can be seen in these figures, the damage was concentrated at the base of the column (plastic hinge area) in the loading direction, as reported in [32]. In general, all the specimens experienced four stages of failure: cracking, yield, ultimate, and rebar buckling, despite varying material strengths, spacings, and axial load ratios. The six columns' failure process was similar; therefore, it can be concluded that NEWRC columns have a failure process similar to that of the BMRC column. No apparent cracks were observed on the specimen surfaces at the initial loading stage for all the specimens, as the deformation was in the elastic range. However, as the lateral load increased, flexural cracks began appearing at the base of the column. Longitudinal rebar was observed to yield around a 1.8-2.0% drift ratio for all specimens. BMRC1 achieved its peak load when the drift ratio was around 2-3%, whereas all the NEWRC columns achieved their peak load when it was approximately 2.5-4%. After the NEWRC column reached its peak load, extensive cover concrete cracks extended upwards from the column base, eventually leading to spalling of the cover. However, for BMRC1, less spalling was observed. Hence, the spalling of the cover concrete was more extensive in NEWRC columns at a lower drift ratio than BMRC1. NEWRC4 experienced more transverse cracking and damages during each drift ratio than NEWRC1, which indicates that the cracking load increased with an increase in axial load ratio. Figure 4: Loading protocol. Figure 5: Crack pattern of damage at the end of the test: (**a**) BMRC1; (**b**) NEWRC1; (**c**) NEWRC2; (**d**) NEWRC3; (**e**) NEWRC4; (**f**) NEWRC5. In specimens NEWRC2 and NEWRC3, due to the increase in transverse reinforcement spacing, longitudinal rebar buckling was observed at an earlier drift ratio of around 4-5%, compared to around 7% for NEWRC1. Furthermore, the longitudinal rebar buckling eventually led to shear strength degradation, with more flexural-shear cracks being observed in the specimens NEWRC2 and NEWRC3. Comparing the behavior of NEWRC1, NEWRC2, and NEWRC3, the transverse reinforcement ratio was identified as the main contributing factor in the failure of NEWRC columns, as less amount of transverse reinforcement ratio can lead to early failure of columns. The failure process of NEWRC5 was identical to that of NEWRC1; both failed due to longitudinal rebar buckling. Hence, it can be concluded that the use of HSR transverse reinforcement cannot avoid longitudinal rebar buckling, and its replacement with the NSR in NEWRC5 had no apparent effects on its failure process. Therefore, it can be concluded that the spacing of transverse reinforcement has more influence on the longitudinal rebar buckling than the strength of transverse reinforcement. In this section, specimens BMRC1 and NEWRC1 were selected to analyze the influence of material properties on the failure process. The cracking and failure process corresponding to each drift ratio level for the specimens BMRC1 and NEWRC1 is shown in Figure 6. In the early stages (around 0.5-2% drift ratio), BMRC1 had more cracks on its surface than NEWRC1. Both specimens achieved their peak load around a 2-3% drift ratio. However, there was a difference between their failure processes after reaching the peak load. In BMRC1, there was no sudden drop in the lateral load, and less cover concrete spalling was observed. However, NEWRC1 experienced a sudden drop in the lateral load, and more cover concrete spalling was observed. Even though more surface cracks and spalling were observed in NEWRC1, it maintained its core integrity and performed well. BMRC1 and NEWRC1 failed at 8% and 9% drift ratios, respectively, due to the longitudinal rebar buckling and concrete crushing.