PSI - Issue 62

6

Adalgisa Zirpoli/ Structural Integrity Procedia 00 (2019) 000 – 000

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

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As an example, Fig. 4 shows the prescribed displacements in Midas Civil, resulting from the analysis of the first stage in Flac3D.

Fig. 4. Prescribed displacement back from Flac3D to Midas Civil in stage 1.

For every stage the user can perform the structural checking in Midas Civil, based on more realistic internal forces arising from the interaction with a continuous modeled soil, characterized by elasto-plastic properties in accordance with specialized constitutive relationships for geotechnical materials. 4. Advantages of the interoperable approach and conclusions This article has presented an alternative methodology to the commonly used interoperable approach of importing the support reactions of the superstructure into the geotechnical analysis environment, obtained from the structural software. This technique has the limitation that the foundation response is independent of the superstructure's stiffness. Moreover, this approach implicitly assumes that the exact load distribution of the superstructure does not impact the soil response. While these assumptions might be acceptable for small structures or based on the analysis's ultimate purpose, in scenarios like bridges this approach appears at least restrictive, if not inapplicable. Let’s, fo r example, think about the landslide risk as a critical parameter influencing the overall structural integrity. It signifies that possessing an advanced structural software, which facilitates the modeling of tapered beams, composite sections, pre- and post-tensioned cables, phase analysis, and even long-term effects like creep and shrinkage, proves to be of limited utility when the structure is imperilled by a foundation failure caused by ground movement on a hillside. In such a scenario, there arises a demand for specialized geotechnical software capable of forecasting the comportment of the abutment, while simultaneously delineating how this instability impacts the structural elements. The most precise method for achieving this objective lies in the execution of an exhaustive soil-structure interaction analysis and the verification of structural constituents through the utilization of the actions derived from the comprehensive system analysis. This necessitates a dual iterative process, wherein the structural rigidity of the bridge is incorporated into the geotechnical analysis, and structural assessments are conducted using the forces and stresses acquired from the comprehensive system calculations. Given our engagement with existing structures, the consideration of pushover analyses also becomes imperative. These analyses constitute a highly preferred approach for evaluating structural vulnerability. They facilitate the maximization of material properties to obtain risk indicators that cannot be ascertained through linear analysis methods. In reference to pushover analyses, it is a common knowledge, whether acquired through formal training, scholarly literature, or general discourse, that anchoring the structure to the ground is an essential practice. It is essential to underline that this recommendation does not stem from a desire to represent reality faithfully (which it does not) or emerge from an academic source, but rather, it arises from the fact that, when conducting a refined analysis (though not as complex as dynamic integration), it becomes illogical to model the soil using a simplistic elastic bed approach. Moreover, such elastic constraints only serve to enhance the structural rotation capacity, which inadvertently affects the outcomes of the pushover analysis, where the primary objective is to gauge the displacement capacity. Representing the soil in a simplified manner, like by springs, would artificially inflate this capacity. Naturally, the situation would be different if a refined non-linear relationship were ascribed to the springs simulating the soil. However, deriving such a relationship poses a formidable challenge, given the inherent