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

Performance‑based evaluation of reinforced soil retaining structures often relies on numerical analyses that require substantial time and expert judgment due to 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 Finite Displacement Method (FFDM). The resulting curves resemble the monotonic pushover curves widely used in structural engineering, indicating that the framework is aligned with established performance‑based methodologies. The method is demonstrated by revisiting the Tanada Wall, a geosynthetic reinforced soil retaining wall with a full height rigid 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: explicit incorporation of peak soil strength and post peak degradation along the slip surface; direct use of peak ground acceleration (HPGA/g) as input, avoiding uncertainties in selecting representative seismographs; and capability for back analysis, enabling soil parameters calibrated from small observed displacements to be used for predicting performance under stronger shaking. A conceptual back analysis procedure is introduced to illustrate this potential.