Ultra-high performance concrete (UHPC) is a newly emerging cementitious composite with superior mechanical performance. Compared with reinforced concrete (RC), UHPC has high compressive strength, toughness and durability, which is gradually promoted for application in the superstructure of bridges such as girders to reduce weight and increase the span length. However, it still lacks an in-depth study regarding the use of UHPC in bridge piers to improve structure performance and the assembly property of the piers.
In this paper, four types of piers with the same dimensions are designed to investigate the optimization design of UHPC-RC composite piers: a common RC column pier, a hollow UHPC pier with the core RC concrete at the top and bottom of the column, a solid UHPC-RC composite pier with the asperity contact, and a solid UHPC-RC composite pier with short connecting steels. Four column models with a reduced-scale 1:10 were adopted to study the performance and load transfer mechanism of the RC and UHPC composited structures.
According to the finite element analysis in Abaqus, the UHPC-RC composite piers with short connecting steels realized the largest axial carrying capacity, which is double that of the RC pier, and the capacity of the hollow UHPC-RC pier was also superior to the RC pier. The results are consistent with the results of the axial compression tests, in which the UHPC-RC shows a larger axial carrying capacity and the failure modes of each case are different. The hysteretic behavior of the UHPC-RC case with short connecting steels is better than the one without connecting steels according to simulation results. Therefore, the hollow UHPC-RC composite piers can achieve good mechanical performance and reduce the amount of concrete as well as the weight of the piers, which is beneficial for the transport and assembly of precast piers in engineering applications.