On the other hand, the shell concrete in specimen 0-1-2 cracked though the column and suffered buckling and loading. Due to the absence of the inner tube from this configuration, the crushed and collapse of the concrete occurred atin the regions where the outer tube had yielded, as illustrated in Fig. 13-b. Continuously, micro-cracksMicro-cracks are developedcontinuing to develop in the concrete as there are increases in the expansion rate of concrete onin parity with steel tubes.