PSI - Issue 81

Dhanies Wahyu Ardyrizky et al. / Procedia Structural Integrity 81 (2026) 458–464

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effects as shown in Fig. 4. The temperature load was defined using a temperature amplitude curve (Fig. 3) that represents the entire fire event from ignition, peak temperature, and subsequent cooling back to the initial temperature. Boundary conditions were applied by pinning both ends of the model, restraining all translational motions while allowing rotation about the Z-axis, as shown in Fig. 4. For the fire-condition simulation, the sandwich panel was modeled using Thermal Coupled Displacement analysis in Abaqus. The simulation was designed to represent realistic fire exposure that may occur in the structure.

Fig. 4. Boundary conditions of the model.

During the meshing process (Fig. 5), quadrilateral S4RT elements with a 50 mm element size were used, consistent with the reference by Klanac et al. (2005). The S4RT element can receive temperature variables from transient thermal analysis and simultaneously compute mechanical response. In the mesh convergence study, the mesh size was varied from 30 mm to 75 mm in 5 mm increments. Quadrilateral elements were selected due to their numerical stability and ability to represent stress and strain distributions more evenly than triangular elements (Mahran et al., 2017). The element size was refined and consistently maintained to accurately capture stress and strain distribution across the face sheets and core layers (Manet, 1998). This study aims to observe and compare both the computational performance and the resulting accuracy.

Fig. 5. Mesh configuration on the sandwich plates.

4. Results and Discussion After all numerical simulations were completed, this section explores the structural reaction to fire, including the displacement and axial force response of the structure. Fig. 6 illustrates the distribution of Von Mises stress on the sandwich panel throughout one complete fire cycle, encompassing both the heating and subsequent cooling phases. During heating to 800°C, the stress decreases as the steel softens, reducing its structural stiffness. Most of the stress is concentrated in the support regions, indicating restraint against thermal expansion. During the cooling process back to the initial condition of 27°C, residual stresses form due to nonuniform recovery of material stiffness between layers, leading to thermal contraction. Temperature variations induce stress reversals and residual stress, which significantly affect post-fire structural integrity.