## 1 Introduction  
Concrete bridges are expected to present excellent seismic performance to assure serviceability and safety [1]. The collapse of concrete bridges is mainly attributed to insufficient lateral deformability, ductility, toughness, and energy dissipation of bridge piers [2]. There are several methods to enhance the deformability and ductility without a significant reduction in the strength of bridge piers. The plastic hinge region of bridge beams and piers have been noted as the weak points and more likely damage locations under impact or earthquake loadings. This is because of the damage accumulation during seismic loadings, eventually leading to the collapse of the whole structure. Increasing the amount of reinforcement stirrups and modifying the form of stirrups in the plastic hinge region are possible approaches, however, the performance enhancement is limited [3, 4]. The confinement at the plastic hinge region is one effective way to strengthen and repair bridge piers. Many confinement materials such as steel tube [5], fiber-reinforced polymer (FRP, [6]), engineered cementitious composites (ECC, [7]) and ultra-high-performance concrete (UHPC, [8]) have been explored to provide external constraints. However, it is difficult to repair the reinforced concrete bridges if containing buckled and fractured reinforcement after earthquake exposure [9]. Many other efforts have been made to utilize the superior tensile strength and ductility advanced concretes for segmentally constructed bridge piers. Concretes such as ECC and UHPC are chosen for the plastic hinge region to provide better seismic resistance [10; 11; 12]. Besides, the design and installment of reinforcement bars can be simplified with these advanced materials. A combination of two or more of the above technologies can better improve the seismic performance of bridge columns [13; 14; 15; 16]. ECC features remarkable higher uniaxial tensile strength as well as tensile strain capacity in the range of 3-5%, compared to 0.01% for ordinary concrete. The excellent tensile characteristics of ECC are attributable to the unique multi-cracking mechanism. With the well-dispersed microfibers in ECC, many evenly spaced microcracks are created under uniaxial tension, rather than a few large macroracks for ordinary concrete [17]. The composition of ECC is custom-tailored through micromechanics design; only fine particles are used in the mixture to achieve a very dense microstructure. At early developments, polyethylene (PE) and oiled polyvinyl alcohol (PVA) fibers were the two most commonly used polymer fibers for ECC. The initially used high-modulus PE fiber used by [PERSON] [18] was very expensive, so that greatly increases the cost. The oiled PVA fiber was approximately 1/8 that of high-modulus PE fiber, but the cost was still very high, compared to ordinary concrete [19]. Later on, many other types of polymer fibers, such as polypropylene (PP) and hydrophilic PVA (HPVA) fibers, were used to make ECC more cost-effective [20]. In this study, domestic PP fiber was used to produce cost-effective ECC. Such a product is called a polypropylene fiber-reinforced engineered cementitious composite (PP-ECC). PP-ECC has been a competent construction material in seismic regions. Previous studies have demonstrated that PP-ECC for beam-column joint connections, columns, beams, and shear walls have significant enhancements of the mechanical performance [21; 22; 23; 24]. [PERSON] et al. [25] observed that PP-ECC concrete cylinders exhibited greater compressive strength and better deformability than pure concrete ones. [PERSON] et al. [21; 26] found that PP-ECC was effective in replacing transverse reinforcements, providing sufficient shear strength, and dissipating more seismic energy. [PERSON] and [PERSON] [27] concluded that PP-ECC exhibited enhanced strength and energy dissipation capacity when subjected to reverse cyclic loading.