Performance-Based Seismic Resistance Assessment of Reinforced Slopes Using the Force-Equilibrium Finite Displacement Method

Performance‑based evaluation of reinforced soil retaining structures often depends on numerical analyses that require substantial time and expert judgment because of the complex interactions among soils, reinforcements, facings, and seismic loading. This study presents an efficient approach for developing seismic resisting capacity curves for reinforced slopes, using a computer program based on the Force‑Equilibrium‑based Finite Displacement Method (FFDM). The resulting seismic‑resisting curves closely resemble the monotonic pushover curves widely used in structural engineering, underscoring that this framework is conceptually aligned with established performance‑based methodologies rather than standing alone. The method is demonstrated through a re‑examination of the Tanada Wall, a geosynthetic reinforced soil retaining wall with a full‑height rigid panel facing that experienced strong shaking during the 1995 Hyogoken‑Nambu earthquake (ML =7.2). Using parameters available in published databases, the FFDM generates realistic seismic resistance curves and directly computes seismic displacements. Three advantages distinguish the FFDM from LEM‑based Newmark approaches: (1) explicit incorporation of peak soil strength and post‑peak degradation along the slip surface, eliminating empirical strength adjustments; (2) direct use of peak ground acceleration (HPGA/g) as input, avoiding uncertainties in selecting representative seismographs; and (3) capability for back‑analysis, allowing soil strength and deformation parameters calibrated from small observed displacements to be used for predicting performance under stronger shaking.