Finite element analysis of prestressed concrete spun pile strengthened with circular thin steel sheet under lateral static pushover load

Prestressed concrete spun piles provide excellent axial capacity but exhibit limited seismic resistance due to an inherently low transverse reinforcement ratio, leading to brittle failure. This study proposes a novel retrofitting technique using discrete, bolted thin steel sheets to enhance flexural performance effectively. The innovation lies in the material efficiency and constructability of discrete sheets compared to continuous jacketing, while simultaneously mitigating global buckling risks. A 3D nonlinear finite element model was developed and validated against experimental cyclic tests of spun piles with and without concrete infill. The validated model was then employed in a monotonic pushover analysis of a soil-structure interaction case study. Results demonstrate that the proposed technique significantly improves displacement ductility (by 34.4%) and provides a modest increase in lateral load capacity (by 4.6%) compared to non-retrofitted piles. Stress–strain analysis confirmed effective concrete confinement by the steel sheets. A parametric study established 3.2 mm as the optimal sheet thickness, a finding consistent with ATC-32 design equations. This retrofitting method presents a cost-effective and constructible solution for enhancing the deformation capacity of existing spun pile foundations, with promising implications for seismic performance improvement.