## 3 Test Results and Analysis
### Mechanical Properties
#### 3.4.3 Ductility  
The ductility is expressed by the displacement ductility coefficient. The ductility coefficient (\(\mu=u_{\text{u}}/u_{\text{y}}\)) is calculated according to the load-deformation curve. \(u_{\text{u}}\) is the displacement value of the corresponding point when the peak stress drops to 85% (When the load does not decrease to 85% \(N_{\text{u}}\), the maximum displacement is taken). \(u_{\text{y}}\) is the initial yield displacement, which is determined by energy equivalence method, as shown in Figure 15, where the dimension of \(OAB\) is equal to the dimension of \(YUB\).  
It can be observed from Figure 16 that, the variation of the displacement ductility coefficient of each member after experiencing different high temperatures. From Figure 16a-h, it can be seen that the displacement ductility coefficients of each member fluctuate up and down with the maximum temperature. In general, the displacement ductility coefficient of various members decreases with the increase of maximum temperature in the range of 200-400 \({}^{\circ}\)C. For the maximum temperature of 400 \({}^{\circ}\)C, the displacement ductility coefficients of prism specimens decrease by 10%, the displacement ductility coefficients of SRRAC columns, SRRAC bending beams, and SRRAC shear beams decrease by 28%, 44%, and 31%, respectively. The displacement ductility coefficients of RRAC columns increase by 2%, while the displacement ductility coefficients of RRAC bending beams and RRAC shear beams decreased by 11% and 51%, respectively. When the maximum temperature is larger than 400 \({}^{\circ}\)C, the displacement ductility coefficient of each member increases, and the displacement ductility coefficients of SRRAC members and RRAC members vary by -25%-4% and -54%-27%, respectively.  
It can be observed from Figure 16i that, the replacement percentage has different effects on the displacement ductility coefficients of different members. The displacement ductility coefficient of prism specimens is less affected by the replacement percentage, and the variation range is -5%-2%. For SRRAC members, the displacement ductility coefficient of bending beams increases first and then decreases, it increases by 63% when the replacement percentage is 70%, and it decreases by 24% when the replacement percentage is 100%. The displacement ductility coefficient of columns and shear beams varies slightly with the replacement percentage, ranging from -5% to 10%. For RRAC members, with the increase of replacement percentage, the displacement ductility coefficient of columns increases first and then decreases, it increases by 10% when the replacement percentage is 50%, and it decreases by 17% when the replacement percentage is 100%. The displacement ductility coefficient of bending beams and shear beams is greatly affected by the replacement percentage, which varies from 24% to 34% and -9% to 41%, respectively. When the replacement percentage is 30%, shear beams decreased by 9%, and the other replacement percentage increased, indicating that the increase of RCA increased the ductility of the beam to some extent.  
In summary, compared with SRRAC members, the ductility of RRAC columns and RRAC bending beams is slightly better, but the ductility of RRAC shear beams is worse. The replacement percentage has a greater influence on the displacement ductility coefficient of RRAC shear beams than SRRAC members, and the displacement ductility coefficients of columns and flexural beams are approximately the same with the increase of replacement percentage.