## 1 Introduction  
A prestressed segmental assembled pier can effectively reduce the residual displacement after an earthquake due to its self-centering ability. It can also greatly improve the construction efficiency because of the assembly property. However, the pier also has its disadvantages: the joint at the pier bottom section is seriously damaged under the action of an earthquake, and the energy dissipation capacity is low in earthquakes, so it is difficult to make popular in high-intensity areas. In recent years, a lot of relevant research has been conducted on these problems. With the improvement in segmental connection and assembly technology, some precast pier structures with high vertical bearing capacity and suitable for high-intensity areas have been proposed and studied. The segmental precast concrete-filled steel tubular pier is one of them. Due to the strong axial bearing capacity of concrete-filled steel tubular, scholars both domestic and foreign apply it to segmental assembled piers and a lot of research has been conducted [1], which has important guiding significance and great development potential for the popularization of segmental assembled piers in high-intensity areas. Concrete-filled steel tubular pier columns have reliable vertical and horizontal bearing capacity [2]. During the prefabrication, the steel pipe can become the side formwork of concrete, which has good economic benefits and constructability. The stress concentration of bonded prestress can be reduced by adopting unbonded prestress. At the same time, it can also avoid the local crushing of concrete caused by the penetration of prestress between segments [3]. At present, there are relatively many, mature studies on the performance of concrete-filled steel tubular structures, while the application of concrete-filled steel tubulars in segmental assembled piers and their performance need more thorough and detailed research [4]. [PERSON] [5] et al. conducted the test of wrapping the pier body with steel pipe in the plastic hinge area at the bottom of the pier, in order to give full play to the advantages of a concrete-filled steel tube and prevent the damage of the pier in the plastic hinge area. However, this practice leads to the plastic hinge moving up to the joint of the upper section, causing serious damage. [PERSON] and [PERSON] [6] replaced all reinforced concrete sections with concrete-filled steel tubular sections and added damping energy dissipation devices at the joint joints. The test shows that this kind of pier has good flexural performance and ductility, does not bring large residual displacement, and the energy dissipation is also improved. [PERSON] [7,8] took advantage of a series of advantages, such as high bearing capacity and good seismic performance of concrete-filled steel tubular piers, combined with the stress characteristics of medium and low piers of long-span short pier continuous rigid frame bridges, and takes Xi'an Weihe River Bridge as the engineering background, as the substructure adopts concrete-filled steel tubular piers. It is found that concrete-filled steel tubular piers can greatly reduce the seismic response of the structure, and have better ductility and energy dissipation capacity than concrete piers. Therefore, this kind of pier can be used as an ideal form of bridge pier column in a high-risk earthquake area. [PERSON] [9,10] introduced the design method of the main components of the prestressed segmental assembled concrete-filled steel tubular pier, and carried out the pseudo-static test of this kind of pier. It is found that this kind of pier has poor energy dissipation capacity without an additional energy dissipation device, and the addition of a connecting steel pipe at the segmental assembly joint can improve the energy dissipation effect, but increases the residual displacement of the pier top. In recent years, the development of seismic engineering research in China has shown a trend from earthquake resistance, vibration reduction and isolation to recoverable function [11].