# Experimental Study on the Seismic Performance of Recycled Concrete Hollow Block Masonry Walls
## 4 Test Analysis
### Energy Dissipation Capacity  
Energy dissipation performance refers to the energy dissipation capacity of the wall under the action of the earthquake load, which is obtained by calculating the area enclosed by the overall hysteresis loop of the first loading cycle. It is an important indicator to measure the seismic performance of the structure. The curves of energy dissipation per cycle are presented in Figure 12.  
As shown in Figure 12a, the energy dissipation increases with the increasing lateral displacement, and the energy dissipation of W2 was the best, then the next was W1, and the worst was W3. Comparing of W1 and W2, the energy dissipation capacity of W2 was higher, indicating that, within a certain range, the vertical compression had a positive influence on the energy dissipation capacity of the specimens. The energy dissipation of W3 was lower compared with W2, indicating that increasing the aspect ratio could decrease the energy dissipation capacity of specimens.  
The energy dissipation curves of the specimens W4 and W5 are shown in Figure 12b. The specimens W4 and W5 were found to have a higher energy dissipation in comparison with the bare walls, indicating that the structural columns could significantly increase the energy dissipation capacity of walls.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Specimen**} & \multicolumn{3}{c}{**Secant Stiffness (kN\(\cdot\)mm\({}^{-1}\))**} \\ \cline{2-4}  & **Initial Point** & **Cracking Point** & **Ultimate Point** \\ \hline W1 & 79.38 & 52.53 & 21.95 \\ W2 & 60.67 & 44.51 & 14.12 \\ W3 & 35.95 & 24.76 & 6.04 \\ W4 & 1017.44 & 234.25 & 25.26 \\ W5 & 611.59 & 251.24 & 22.53 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Secant stiffness of all the specimens at characteristic points.  
Figure 12: Energy dissipation per cycle for all test specimens: (**a**) W1, W2, and W3; (**b**) W4 and W5.  
To further quantify the hysteretic energy dissipation performance of the specimens, the equivalent viscous damping coefficient is used to measure the energy dissipation capacity of the structure under earthquake resistance. \(h_{e,u}\) and \(h_{e,f}\) are the equivalent viscous damping coefficients corresponding to the maximum load and the ultimate load, respectively. The equivalent viscous damping can be calculated as follows:  
\[h_{e}=\frac{1}{2\pi}.\frac{S_{ABC}}{S_{AOBD}}\]  
where \(S_{ABCD}\) and \(S_{ABC}\) are the areas enclosed by the shaded hysteresis loop in Figure 13, respectively.  
The value of the equivalent viscous damping coefficient and energy dissipation per cycle can be observed from Table 7 and Figure 13, respectively. In comparison with W1, the value of \(h_{e,u}\) of W2 was 18.6% higher than that of W1, which indicated that the vertical compression could increase the energy dissipation performance of specimens. In terms of W2 and W3, the value of \(h_{e,u}\) of W3 was 54.8% lower than that of W2, which illustrated that increasing the aspect ratio had a negative influence on the energy dissipation performance of specimens. It should be noted that W1 and W3 were almost destroyed after reaching the ultimate load, and the hysteresis curve of W2 was not closed when the specimens were destroyed. Therefore, the value of \(h_{e,f}\) of W1, W2, and W3 was ignored.  
It can be easily found that the value of equivalent viscous damping ratio of W4 and W5 were more significant than that of bare walls, which illustrated that, whether each of the specimens were constrained by ordinary concrete structural columns or RAC structural columns, the equivalent viscous damping ratio and the energy dissipation of the walls were improved. Compared to W4, the energy dissipation viscous damping ratio of W5 exhibited a 12.5% and 8.9% increase at maximum load and ultimate load, which illustrated that the energy dissipation capacity of ordinary concrete structural columns was close to that of RAC structural columns.