## 3 Results and Discussion
### Visual Observation and Failure Modes  
Figures 6-8 show the post-failure overview of the tested columns of CC, GC, and GCD groups, respectively. The key factors that affected the failure modes of tested columns are the existence of steel fibers and loading conditions. A sudden brittle failure was observed in all the columns subjected to concentric loading with lower residual loading capacity. The concentrically loaded specimens were failed abruptly by concrete crushing, whereas typical flexural failure mode was observed in columns subjected to eccentric loading. Firstly, longitudinal cracks were observed in eccentrically loaded columns. The initial cracks were formed in between a region of 100-200 mm from the mid-height section to the ends of columns. On increasing the load, these longitudinal cracks extended along the height of the column, followed by concrete crushing. The location of the failure zone in tested columns varies from the mid-height section to an extreme of 350 mm below or above mid-height. The failure mode and crack pattern of tested columns varied depending on the eccentricity. By comparing the failure modes of columns tested under different eccentricities, it was observed that the number of cracks increased with the increase in eccentricity. The spalling of concrete cover was observed in all plain CC, GC, and GCD tested columns. It was also observed that the cover concrete of all specimens (without fibers) spalled out in between a region of 200-300 mm from the ends of columns, while the core concrete was intact. On the contrary, no cover spalling was observed in all fiber-reinforced GC and GCD columns.  
All the fiber-reinforced columns of GC and GCD groups were failed in a similar manner. The columns tested under concentric loading (GC-0.75F-0E and GCD-0.75F-0E) experienced a brittle failure mode with localized concrete crushing at the top or bottom face of the column. Meanwhile, the columns tested under eccentric loading were failed with the development of longitudinal flexural cracks, followed by disintegration of the concrete cover. The failure modes of all fiber-reinforced columns of GC and GCD groups are shown in Figures 7 and 8, respectively. The axial load-displacement response of CC, GC and GCD group columns are presented in Figures 9-11. The cracking can be observed throughout the surface of all fiber-reinforced GC and GCD columns. Firstly, longitudinally, cracks were developed either at the top or bottom end of the fiber-reinforced columns. As the load was increased gradually, these longitudinal cracks were prolonged along the height of columns, followed by the disintegration of the concrete cover. All the fiber-reinforced specimens were characterized by the formation of surface cracks around one-third height from the support. The general behavior of the GC group columns is observed to be similar to that of GCD group columns, in which the peak axial load (P\({}_{\text{max}}\)) and axial displacement at peak axial load decreases with an increase in the load eccentricities (15 to 35 and 50 mm), as depicted in Figures 10 and 11, respectively. Meanwhile, the lateral displacement tends to increase with the increase of eccentricity due to the tendency of columns to buckle under eccentric loading, as shown in Figures 12 and 13.