## 4 Test Results and Discussion
### Envelope Curves  
A thorough consideration of the maximum loading observed at each loading step of the tested specimens and, consequently, of the efficacy of the proposed strengthening  
Figure 8: Seventh loading step. Comparisons of the response cycles of the 7 th loading step of the two specimens: (**a**) the first cycle of the loading step, (**b**) the second cycle of the loading step, (**c**) the third cycle of the loading step.  
Figure 7: Fifth loading step. Comparisons of the response cycles of the 5 th loading step of the two specimens: (**a**) the first cycle of the loading step, (**b**) the second cycle of the loading step, (**c**) the third cycle of the loading step.  
Figure 9: Comparison of the hysteretic response cycles of the two specimens. The values of the loading of the strengthened specimen JC0 VF2X2c appears to be higher than the corresponding ones of the other specimens in all loading cycles. The differences increase in the 6 th and 7 th loading steps.  
method in terms of the load capacity and ductility can be obtained through the obtained hysteretic responses. In order to succinctly determine the differences in the observed maximum loads per loading step between the pilot (JC0V) and the strengthened (JC0V2X2c) specimen, a comparative presentation of the envelope curves of the two specimens is shown in Figure 10.  
In particular, envelope curves of the maximum observed loads of the first cycles of each loading step are shown Figure 10a; further, envelope curves of the maximum loads of the second cycles of each step are shown in Figure 10b; similarly, envelope curves of the maximum loads of the third cycles of each step are shown in Figure 10c.  
The damages of the pilot specimen were located in the columns and especially in the joint panel. The developing damage in the joint panel is mainly attributed to an X-shaped shear cracking system that eventually led the specimen to shear failure. On the other hand, the damage of the strengthened column appeared and remained in the beam close to the column, whereas the character of the appeared cracks were purely flexural. Therefore, the observed differences in the cyclic response of the two specimens can mainly attributed to the character of the developing damages.  
Figure 10: Comparison of the envelope curves of the tested specimens: (**a**) envelope curves of the maximum loads at the 1 st cycles of each loading step, (**b**) envelope curves of the maximum loads at the 2 nd cycles of each loading step, (**c**) envelope curves of the maximum loads at the 3 rd cycles of each loading step.  
The observed maximum loads per loading cycle of all loading steps of the tested specimens JC0 VF2X2c and JC0V are shown in Table 1. Moreover, the ratios of the maximum loads per loading cycle are also shown in the same Table 1. The differences between the envelope curves of the tested specimens confirm the expected conclusion that the externally applied C-FRP ropes to the column of JC0V2X2c specimen significantly improved the cyclic response of the specimen compared to the response of the other specimen with the unstrengthened column (pilot specimen).  
It is also emphasized that sudden drops of the envelope curves of the tested specimens are observed in Figure 10. These drops are more intense in the unstrengthened specimen since its failure mechanism is mainly of shear character, whereas the final failure mechanism of the strengthened one has a clear flexure character. Further, as it can be noted for the unstrengthened specimens (Figure 10), the sudden drops begin at earlier steps compared to the strengthened one.