PSI - Issue 75

Bruno Depale et al. / Procedia Structural Integrity 75 (2025) 254–261 Bruno Depale/ Structural Integrity Procedia (2025)

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3.2. Railway traffic and train line-ups after the French domination (1955-2024)

From 1955, the French car fleet was completed by locomotives, train carriages and freight cars fabricated in Czech Republic, Romania or China. The traffic data collection of this 1955-2024 period comes from the archives of Vietnam Railways (Đườ ng s ắ t Vi ệ t Nam, DSVN) located at Hanoi. Keeping the same previous four types of train, data collection shows a global decrease of traffic and a decrease in the number of carriages/cars for each type, average loading remaining similar. The total number of trains circulating on LBB during the 1955-2024 period can be reliably estimated evaluated at 594,000. 4. Our Finite Element Model of LBB Our CAD of the model file of the first six spans of LBB has been created with AUTOCAD and SolidWorks software, using the geometrical dimensions and thicknesses from the original drawings of Daydé & Pillé. This data has been completed by measurements on site and loss of thickness due to corrosion considered. Then, based on this 3D CAD, the model file has been built with Abaqus software where the characteristics of the cross-sections have been included (see Fig. 4. (a)). The model file is mainly composed of beam elements (Abaqus B31).

Fig. 4. (a) Model file of the first four spans of LBB, (b) specific cross-sections (selection)

Many LBB ’s beams are assembled from multiple L-shaped steel plates using riveted connections, so their cross sections are not available in Abaqus' profile library. It was therefore necessary to carry out manual operations to create these specific sections, calculate the moments of inertia of each section, and then assign them to the corresponding beams (See examples of such specific cross-sections in Fig. 4. (b)). The modelling of the connection between two spans, at the extremity of a cantilever, required modelling with shell elements (S4R and S3R Abaqus elements) because stresses and loads in these local areas cannot be correctly calculated with beam elements (see Fig. 5.). Subparts in shell and beam elements are connected by the TIE function. The relevant boundary conditions are applied for the modeling of the support provided by fixed bearings and expansion bearings, between girders and pillars. The steel structure is made of puddle iron with following modulus of elasticity: E = 170 000 MPa. The global Abaqus model file represents 9,717 nodes and 7,774 elements.