Seismic site instability is driven by two primary mechanisms: increased shear stress caused by wave propagation, which can result in slope failure or landslides; and a reduction in effective stress caused by excess pore-water pressure, which can result in liquefaction and/or settlement. Both processes severely reduce the shear modulus and shear strength of soils. Rigorous seismic analysis requires sophisticated computational frameworks incorporating advanced constitutive models that simulate soil failure using elasto-plasticity and volumetric-distortional coupling. In practice, however, the effectiveness of these models is limited by the difficulty of calibrating their extensive parameter sets reliability. A practical middle ground between scientific exactitude and applied utility can be found in simplified analytical procedures. Many of these approaches operate in a decoupled domain, separating the initial calculation of seismic ground motion (typically solved under free-field boundary conditions) from the subsequent estimation of response metrics (e.g., permanent displacement or Cyclic Stress Ratio (CSR)) via empirical or semi-empirical correlations. While these methodologies are valuable for preliminary hazard screening, they often fail to adequately replicate the highly nonlinear soil response observed as failure conditions are approached. Specifically targeting liquefaction potential, the SCOSSA 2.0 numerical code integrates a simplified stress-based pore pressure generation model within a cyclic response analysis framework, coupled with one-dimensional consolidation theory. This next-generation code performs a loosely-coupled effective stress analysis under both fully drained and partially drained conditions. This note summarises the main calculation strategies adopted for numerical solutions within the SCOSSA code, focusing on the technical developments that necessitated an update to the software.
Performance-Based Assessment of the Seismic Soil Instabilities in the Framework of the Ri-SCOSSA 2.0 Project
Tropeano G.
Primo
Writing – Original Draft Preparation
;Soccodato F. M.Penultimo
Writing – Review & Editing
;
2026-01-01
Abstract
Seismic site instability is driven by two primary mechanisms: increased shear stress caused by wave propagation, which can result in slope failure or landslides; and a reduction in effective stress caused by excess pore-water pressure, which can result in liquefaction and/or settlement. Both processes severely reduce the shear modulus and shear strength of soils. Rigorous seismic analysis requires sophisticated computational frameworks incorporating advanced constitutive models that simulate soil failure using elasto-plasticity and volumetric-distortional coupling. In practice, however, the effectiveness of these models is limited by the difficulty of calibrating their extensive parameter sets reliability. A practical middle ground between scientific exactitude and applied utility can be found in simplified analytical procedures. Many of these approaches operate in a decoupled domain, separating the initial calculation of seismic ground motion (typically solved under free-field boundary conditions) from the subsequent estimation of response metrics (e.g., permanent displacement or Cyclic Stress Ratio (CSR)) via empirical or semi-empirical correlations. While these methodologies are valuable for preliminary hazard screening, they often fail to adequately replicate the highly nonlinear soil response observed as failure conditions are approached. Specifically targeting liquefaction potential, the SCOSSA 2.0 numerical code integrates a simplified stress-based pore pressure generation model within a cyclic response analysis framework, coupled with one-dimensional consolidation theory. This next-generation code performs a loosely-coupled effective stress analysis under both fully drained and partially drained conditions. This note summarises the main calculation strategies adopted for numerical solutions within the SCOSSA code, focusing on the technical developments that necessitated an update to the software.
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