Mechanistic Evaluation of Axial Load Transfer and Bearing Capacity in Small-Scale Steel Sheet Piles for Short-Span Bridge Abutments

Abstract Steel sheet piles are widely used in bridge abutments to retain backfill and mitigate scour; recent applications and case histories also suggest that sheet piles may contribute to axial load resistance for short-span or low-traffic bridges. In this study, modified static axial pile loading tests were performed at a field test site using an instrumented half-scale (50%) model sheet pile to provide experimental evidence and mechanistic insight into axial load transfer under the tested configuration. The test pile was installed by placement in an excavated pit followed by sand backfilling and light compaction to protect instrumentation, and three axial loading tests were conducted. Ultimate capacity was interpreted using Davisson’s criterion, yielding a consistent ultimate axial capacity of approximately 35–37 kN across repeated tests. Load-transfer interpretation based on strain measurements indicates that side friction mobilized the majority of resistance (approximately 70–75%), with the remaining portion carried by end bearing. Analytical, SPT-based, and CPT-based prediction methods were then evaluated against the measured components; overall, analytical and CPT-based approaches provided closer agreement with measured side resistance than the SPT-based methods, which showed greater variability. Measured end-bearing resistance exceeded values predicted by methods using steel-only tip area, suggesting that partial soil plugging may have contributed to the effective end-bearing area; however, plugging was not directly observed and is treated as a bounding assumption. Because the tests employed a downsized pile and a placed/backfilled installation method, the results are best interpreted as mechanistic insight and comparative evaluation of prediction approaches for the tested configuration rather than direct full-scale design calibration.