PSI - Issue 62

Adalgisa Zirpoli et al. / Procedia Structural Integrity 62 (2024) 217–224 Adalgisa Zirpoli/ Structural Integrity Procedia 00 (2019) 000 – 000

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In cases where the structural BIM environment cannot directly interface with the calculation software, we can utilize the IFC format, specifically the 'IFC Analysis Domain' class for analysis-related information. This class contains data necessary for performing static analysis, including loads, constraints, and internal releases. If this specific format is unavailable, the more widely used 'IFC Model View Definition (MVD)' can be employed. Many calculation software packages use IFC MVD as a foundational support to generate the finite element scheme. In such cases, all additional information required for analysis and design must be input manually through the calculation software's graphical interface. Completing the geometric model, particularly in terms of node continuity, might also be necessary. For our proof of concept, we selected ModeSt as our FEM software. ModeSt supports both IFC Analysis Domain and IFC MVD for import. We effectively leveraged a smart synergy between these two formats. The import process occurred in two stages: first using IFC MVD (excluding the tapered sections, which were not manageable) to transfer the set of sections. Subsequently, we imported the model using IFC Analysis Domain, automatically creating a coherent finite element framework. While this framework was sufficient for the analysis itself, post processing operations, such as inputting steel reinforcement, necessitated the use of real 3D sections. Following the automatic generation of a coherent framework, we assigned the sections previously imported via IFC MVD to the elements, providing them with more than just their inertial properties. The slab was then modeled by applying an automatic mesher to the closed areas identified by the longitudinal beams and transoms. We manually assigned sectional offsets within the calculation tool. Given the intricate nature of the geometries involved, several simplifications were necessary before transferring the model. Primarily, the inclined struts, which exhibit variations in section along both their minor and major sides, were modeled with a variable section only along the major side. Furthermore, the connection section to the deck was excluded from the analysis model due to its extremely squat nature, making it unsuitable for modeling as a 1D finite element. Instead, it was treated as a rigid element with the sole purpose of load distribution. Additionally, for the variable-section inclined struts, we performed the analysis as if they had a constant section, choosing the smallest available size. This approach serves as a valid workaround when the employed calculation software lacks tapered finite element sections in its library. This choice ensures a more conservative assessment for sections closer to the deck.

Fig. 4. FEM model.

Another simplification pertains to the Gerber saddle supports. These supports handle loads through complex nonlinear frictional interactions. To facilitate a simpler linear analysis, we substituted the Gerber saddles with beams. The axial and cross stiffness of these beams was assumed with the consideration of no relative sliding between the longitudinal beams. The axial and cross stiffness values were determined based on the shear and normal stiffness of the interface between the beams. Subsequently, reinforcement bars were incorporated. Once the verification results were obtained, we were able to export reports for each load combination or result type (such as shear or bending moment capacity rates or Risk Index) in .pdf format. These reports were then linked to the respective components in the collaborative model. This approach allowed structural engineers to access