## 4 Conclusions  
In this study, the moment-curvature behavior of RC and PP-ECC bridge piers under reversed cyclic loading were experimentally investigated. The affecting factors involved are stirrups ratio, axial compression ratio, and the height of PP-ECC regions. Based on the observations and experimental results, the responses of moment-curvature and reinforcement bars were analyzed accordingly, the following conclusions were drawn:  
(1) The use of PP-ECC at potential plastic hinge regions can effectively improve the damage tolerance of bridge piers, owing to its superior ductility and crack development control. Compared to the PP-ECC bridges piers, RC ones presents lower deformation capacity and obvious concrete crushed after failure;  
(2) The curvature at the plastic hinge region gradually increases with the increase of cyclic lateral loading/displacement level, regardless of the concrete type for the pier. The maximum curvature usually locates at the bottom of the pier. The curvature distribution along with the height has some linear feature under a certain region above the bottom. The curvature distribution is consistent with the failure pattern of the pier under seismic loadings. Based on the curvature distribution along with the height of the pier, it is found that the axial loading ratio has a negative effect on enhancing the rotation capacity and plastic deformability, while the height of the PP-ECC portion and the amount of transverse reinforcement display the opposite trend;  
(3) The moment-curvature hysteretic curves have similar shapes for all piers. With the increase in curvature, the moment increases linearly at first, and is followed by a strong moment-hardening behavior. The maximum moment is observed to locate at the 15 cm from the bottom of pier, so piers most-likely fail near the bottom under seismic activities. It can be obviously seen that PP-ECC is beneficial to the seismic resistance of bridges piers, as greater peak moments and larger areas of hysteretic curves are observed. Based on the moment-curvature analysis, it is observed that PP-ECC piers exhibit better seismic resistance with higher the stirrup ratio or higher axial loading ratio.  
(4) Based on the reinforcement strain measurement, the performances of longitudinal bars and transverse bars are analyzed. The maximum longitudinal strain usually presents the bottom. After reaching the ultimate load, the longitudinal reinforcement bars yield, but the stirrups in the pier do not. The stirrups can effectively constrain the lateral deformation of concrete that improves the lateral deformability of the plastic hinge region. When the pier is loaded to the ultimate load, the longitudinal reinforcement strain of RC piers is much larger than those of PP-ECC ones. In addition, the contribution of stirrups in PP-ECC piers is more obvious than that of RC ones.  
Writing--original draft preparation, Y.J., H.S., F.L., and Y.B.; writing--review, revision and editing, Z.L., and Z.Z. All authors have read and agreed to the published version of the manuscript.  
The National Natural Science Foundation of China with Grant No. 53168027, and the Science Research Foundation of Yunnan Education Bureau with Grant No. 2020J0061.  
The authors declare no conflict of interest.  
All testing raw data, calculation results and more plots not included in the study are available from the corresponding authors by request (list items: 1. Lateral loading versus displacement history; 2. transducers' readings \(h_{1}\), \(h_{2}\); 3. moment-curvature calculation details; 4. lateral loading versus reinforcement strains).