## 3 Experiment Results and Discussion
### Energy Dissipation
#### 3.2.2 Comparative Analysis Based on Different Influencing Factors  
(1) Seismic strengthening effect of the IPCSAM  
As shown in Table 4, the comparison between UP-1 and RP-1, UP-2 and RP-4, and UP-3 and RP-5 with the same length-diameter ratio (i.e., 4, 6, and 8, respectively) indicated that the peak load \(F_{p}\) of RP-1, RP-4, and RP-5, which were strengthened using the IPCSAM, increased by 106.4%, 98.6%, and 83.5%, respectively. The initial stiffness \(K_{0}\) increased by 83.9%, 176.6%, and 177.3%, respectively, and the ductility coefficient \(\mu\) increased by 49.4%, 50.2%, and 16.3%, respectively. In addition, the secant stiffness \(K_{i}\), energy dissipation per cycle \(E_{hi}\), and equivalent viscous damping \(\xi_{qui}\) of RP-1, RP-4, and RP-5 at each loading stage were significantly higher than those of UP-1, UP-2, and UP-3 (Figures 14 and 16). Generally, the bearing capacity, ductility, stiffness, and energy dissipation capacity of the strengthened specimens were significantly improved compared with the unreinforced  
Figure 16: Energy dissipation curves. (**a**) Energy dissipation per cycle; (**b**) Equivalent viscous damping ratio. Figure 15: Calculation diagram for energy dissipation. specimens, indicating that the IPCSAM had a good seismic strengthening effect on pier columns with different length-diameter ratios. Influence of self-stress on the strengthening effect  
As shown in Table 4, the comparison between specimens RP-0 and RP-1 showed that an initial circumferential self-stress of 1.6 MPa increased the peak load \(F_{p}\), initial stiffness \(K_{0}\), and ductility coefficient \(\mu\) of the strengthened specimen by 17.3%, 8.3%, and 43.5%, respectively. Meanwhile, compared with RP-0, the secant stiffness \(K_{i}\), energy dissipation per cycle \(E_{hi}\), and equivalent viscous damping \(\xi_{api}\) of RP-1 improved to a certain extent, and the stiffness degradation rates of the two specimens were similar (Figures 14 and 16). We can conclude that the circumferential self-stress generated by the SSAWC provided active restraint to the core pier column, placing it in a triaxial compression state, which effectively delayed the internal cracking of the pier column and enhanced its bearing capacity, ductility, stiffness, and energy dissipation capacity. Thus, the self-stress produced by the SSAWC significantly improves the seismic performance of strengthened pier columns. Influence of the LCSS reinforcement ratio on the strengthening effect  
A comparison between RP-1 and RP-2 indicated that, with an increase in the reinforcement ratio of the LCSS from 0.25% to 0.5%, the peak load \(F_{p}\), initial stiffness \(K_{0}\), and ductility coefficient \(\mu\) of the strengthened specimens increased by 9.76%, 16.18%, and 22.24%, respectively (Table 4). The secant stiffness \(K_{i}\) also increased slightly during the entire loading process, while the stiffness degradation rates of the two specimens remained relatively constant (Figure 14). We inferred that the increased reinforcement ratio of the LCSS enhanced its tensile strength and stiffness, improving its circumferential constraint effect on the core pier column and ultimately increasing the strengthened pier columns' bearing capacity, ductility, and stiffness. Additionally, the energy dissipation per cycle \(E_{hi}\) of RP-1 was larger than that of RP-2 during the loading process, and the equivalent viscous damping \(\xi_{epi}\) of RP-1 was similar to that of RP-2 (Figure 16), indicating that the increased reinforcement ratio of the LCSS could improve the energy dissipation capacity of the strengthened pier columns to a certain extent. In summary, enhancing the reinforcement ratio of LCSS can effectively improve the seismic performance of strengthened pier columns.