PSI - Issue 62

Adalgisa Zirpoli et al. / Procedia Structural Integrity 62 (2024) 492–498 Adalgisa Zirpoli/ Structural Integrity Procedia 00 (2019) 000 – 000

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1. Introduction and state of the art In recent years, there has been a notable upsurge in the engineering community's interest in the realm of soil structure interaction. This challenge is, undoubtedly, one of the most intricate in the field. Despite the substantial advancements in computational capabilities over the past two decades, coupled with ongoing progress in numerical methods, the integration of structural analysis software with geotechnical concerns remains fairly limited. Specialized structural engineering analysis codes and geotechnical applications continue to exist in isolation from one another. This division primarily stems from the highly specialized demands placed on a solver designed to address geotechnical issues. For instance, consider the intricate issues surrounding water management, particularly in the case of fine-grained soils. Furthermore, there is a necessity to establish an initial stress state with zero deformation to simulate the geostatic phase accurately. Finally, the complexity of the constitutive relationships for soils must be addressed to capture the multifaceted nature of this natural material, which is not man-made and poses substantial challenges for investigation. Nonetheless, it is crucial to incorporate structural works within their geotechnical context, particularly in the case of structures wholly or partially submerged in the ground (e.g., tunnels, retaining structures, bridge abutments, etc.). There is a mutual and reciprocal influence of the stress-deformation state: the stiffness and strength of the foundation determine the response of the structure, which in turn affects the foundation's response. Structural analysis programs often resort to using elastic or elasto-plastic springs, but this approach is insufficient to capture typical soil behaviors, such as stiffness variations due to overconsolidation, variations under virgin or unloading-reloading conditions, boundary effects, and interaction between adjacent structures through the soil. Many projects increasingly demand the need for advanced analyses that harness the full potential on both the structural and geotechnical sides. This underscores the clear necessity of establishing a connection between these two computational domains. Recent regulatory developments and market demands are pushing designers towards complex geotechnical modeling and analysis. On the other hand, structural assessment software for civil works, such as buildings or bridges, must have specific features to ensure a proper safety evaluation of the structure. Typically, the software should be able to perform checks in accordance with current regulations. This entails a range of advanced functionalities that cannot be a mere byproduct of general-purpose geotechnical software. These include features for inserting reinforced concrete rebars, visualizing steel nodes in 3D (which is essential for understanding the design), and defining and applying various types of structural reinforcements. Without delving into complex matters, consider the modeling capabilities of these software tools. Only specialized structural engineering software allows for easy modeling of elements such as beams, walls, and plates (properly connected) to simulate elevated slabs, columns, beams, shear walls, and generate wind loads, floor loads, snow loads automatically. This is typical of structural analysis software and is not as straightforward or applicable in a geotechnical analysis code. In essence, structural analysis software offers a whole realm that is not considered by geotechnical software but can be complementary. In general, establishing a link between these two realms (structural and geotechnical analysis) could help account for: • The actual stratigraphy in accordance with geological-geotechnical surveys • The effect of overconsolidation due to preliminary excavation before foundation pouring • The initial stress state (known as "geostatic") in the absence of subsequent deformation • The confinement provided by the soil above the foundation level outside the excavation area Besides, advanced and specific constitutive relationships for geotechnical materials can be taken into account, which can, for instance: • Simulate strain hardening responses both in shear and volumetric terms • Provide different elastic responses in virgin conditions or during unloading-reloading cycles • Implement a failure criterion • Depict a non-linear stiffness variation even at low deformations or under unloading-reloading conditions