###### Abstract  
Concrete-filled steel tubes (CFTs) offer significant structural advantages in terms of stiffness, strength, and ductility. The concrete core enhances the stiffness and compressive strength of columns, whereas the steel tube serves as a reinforcement to resist tension and bending by confining the concrete. Moreover, CFT columns offer exceptional resistance, such as high strength, ductility, and energy absorption capacity. This study presents experiments focused on prefabricated bridge piers featuring multiple CFT columns. Commercial circular steel tubes were utilized to streamline fabrication efforts, with bracings employed to enhance structural performance by connecting the CFT columns. Component tests were conducted for different connection details to prevent premature failure owing to cyclic loading. A full-scale modular pier was designed to explore its cyclic behavior using the bracing connection details derived from the component test. The plastification location in a modular pier can be designed using the connection details, as validated experimentally. The results of this study indicate that CFT columns, as the main component of the bridge pier, can be protected by designing connection details to induce stress concentration in the braces, thereby achieving ductile behavior. C 2024 14 11810 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11  
the moment capacity of the section, whereas a higher ratio may result in brittle fracture [9]. According to research on the effect of the L/D ratio on CFT members [10], a ratio below 18 provides sufficient plastic moment capacity, whereas higher ratios lead to decreased moment and axial load-bearing capacities. There have been studies addressing considerations for using CFT columns as bridge columns. [PERSON] et al. [11] conducted experimental and numerical analysis on thin-walled CFT priors to quantify the effects of axial compression ratio, concrete filling rate, and seismic load direction on residual displacement. [PERSON] et al. [12] investigated temperature rise due to solar radiation in steel-box CFT towers applied to suspension bridges through laboratory experiments and thermal simulations. Their findings revealed that a 0.11 mm void could form internally due to the thermal expansion difference between steel and concrete, and they emphasized the need for caution regarding the repetitive void formation caused by daily temperature variations. [PERSON] et al. [13] evaluated the seismic performance of post-tensioned precast segmental CFT double-column piers using cyclic loading experiments and parametric analysis through numerical models. Their study found that the number of segments had minimal impact on energy dissipation and strength but did influence the initial stiffness. Additionally, they confirmed that increasing the prestress of PT bars enhanced both the strength and energy dissipation capacity of specimens under constant axial load. Further studies, such as research on the increase in ductility of CFT columns with higher steel strength [14] and behavior evaluation and code comparison of CFT columns with varying concrete strengths [15], have been conducted. However, research on modular multi-column CFT piers remains insufficient. Modularized CFT frames offer a cost-effective solution for designing bridge substructures using commercial steel tubes. In mountainous regions where transportation of equipment and materials is challenging, lightweight and efficient construction methods are essential. CFT columns are ideal for modular structures as they can be easily connected through welds or bolts. Modular structures inherently involve numerous connection points, making high-strength bolted connections a preferred method due to their constructability. To ensure redundancy and structural safety under unpredictable external loads, such as seismic excitations, it is essential to design a structure where multiple CFT columns form a single bridge pier. Consequently, bracing connections are critical for achieving integrity among the columns.