Seismic Performance Analysis of Precast Segmental Assembled Piers Based on Axial–Shear–Flexure Interaction Model: Calculation Program Design and Experimental Verification

To investigate the Axial–Shear–Flexure Interaction (ASFI) of precast segmental assembled bridge piers, this study proposes a connection system using tapered-sleeve locking steel bar joints and fiber-reinforced concrete (FRC). Four 1:2.5-scaled pier specimens—including single- and double-column configurations, with both cast-in-place and precast segmental designs—were tested under quasi-static cyclic loading. The experimental results show that the precast components exhibited comparable or superior seismic performance, with peak loads in single/double columns being 4% and 5% higher than those in cast-in-place components, respectively; the equivalent viscous damping ratio was 2–4% higher, and residual displacement was reduced by approximately 20%. In addition, an ASFI-based calculation program is developed in Python 3.9 to predict the load–displacement response under combined axial, shear, and flexural actions. The program predicts the peak load of all specimens with errors within 10% but systematically underestimates the peak displacement. Deformation decomposition reveals that shear deformation accounts for 2–7% of the total deformation in single-column piers but increases to 10–17% in double-column piers, confirming the necessity of ASFI modeling for shear-critical configurations. This connection system meets the performance requirement of being “equivalent to cast-in-place,” but the program is only applicable to bearing capacity estimation, and its universality requires further parameter verification.