## 6 Shear Deformation of the Connection Panel of the Specimens  
An important deformation parameter that reflects the level of the damage of the part of the column that connects the column with the beam (joint panel) is its maximum shear deformation during the seismic loading. Therefore, the calculation of the shear deformation of the joint panel at each loading cycle is very important for the assessment of the effectiveness of the applied strengthening technique.  
The shear deformations of the joint panel of the tested specimens versus the drift were calculated at each loading step. The comparison of the values of the joint panel shear deformations of the two tested specimens during the testing is an indication for the damage level of the joint panel of each specimen and consequently for the effectiveness of the strengthening technique.  
For the calculation of the shear deformations of the joint panel at a loading point of the testing procedure, the values of the diagonal shortening and the diagonal elongation of the panel at the specific moment have to be measured [41, 42]. These values were continuously measured and recorded during the testing procedure for both the tested specimens of the presented study. For these measurements, two string displacement transducers (String  
Figure 14: Comparative presentation of the maximum absolute values of the steel bars strain as recorded from the strain gauges mounted on the tested specimens. (**a**) Strain gauge SG1 records the strain of the flexural reinforcement of the column at the edge of the connection with the beam; (**b**) strain gauge SG2 records the strain of the flexural reinforcement of the beam at the edge of the connection with the column.  
LVDTs) were used and diagonally mounted on the connection panel of each specimen. In particular, using the two string-LVDTs, the diagonal shortening (Figure 15a) and the diagonal elongation (Figure 15b) of the panel were continuously measured and recorded.  
An estimation of the average shear deformation \(\gamma_{\mathrm{avg}}\) of the connection panel can be calculated based on the following relationship [41]:  
\[\gamma_{\mathrm{avg}}=(\Delta I_{1}+\Delta I_{2})/(\mathrm{L}\cdot\sin 2\phi) \tag{1}\]  
where \(\Delta I_{1}\) is the elongation of the diagonal string-LVDT, \(\Delta I_{2}\) is the shortening of the other diagonal string-LVDT, \(\mathrm{L}\) is the initial length of the strings of the string-LVDTs, and \(\phi\) is the inclination angle of the diagonals of the joint panel (Figure 15).  
Thus, the diagonal elongations and diagonal shortenings of the joint panel of the tested specimens were measured by the two string LVDTs at each step of the loading procedure. Subsequently, the maximum values of the shear deformations of the joint panel of the two tested specimens were calculated based on Relationship 1. The shear deformations of the specimens are presented per story drift in Figure 16. In this figure, the absolute values of the maximum shear deformations of the joint panel of the strengthened specimen JCV2X2c are compared with the corresponding values of the shear deformations of the specimen JCV per loading step and drift. It is apparent that the maximum shear deformations of the connection panel of the strengthened specimen JCVF2X2c are lower than the corresponding ones of the pilot unstrengthened specimen JCV. It is a strong indication that the strengthening technique increases the strength and the stiffness capacity of the column and decreases the deformations and the damages in comparison with the ones of the specimen JCV.  
Figure 15: Shear deformations of the connection body of the column with the beam. Instrumentation and measurement procedure. (**a**) Diagonally mounted string-LVDT for the measurement of the shortening and (**b**) diagonally mounted string-LVDT for the measurement of the elongation of the joint panel.