6. As can be seen
in these figures, the rupture of FRP jackets occurred at themid-height region of the specimens for all cases. Fig. 3(a) and (b)
illustrates that the failure of the unreinforced HSCFFT specimens
resulted from formation of a few major macro-cracks in the concrete.
On the other hand, as shown in Fig. 4(a)–(g), smaller crack
formations were observed in the concretes of SFRHSCFFT and
SIFCONFFT specimens. These observed differences in the failure
modes suggest that the cracking mechanism of the core concrete
was influenced by the presence of steel fibers, which is discussed
in detail later in the paper.