Assessment of the seismic overpressure in flat bottom steel silos based on advanced FE modelling approach

The paper presents a study dealing with the assessment of the dynamic overpressure induced by earthquakes in flat bottom steel silos. Silos are integral components of industrial plants, as part of a complex network of mechanical and structural components. Ensuring the safety of silos is critical in industrial processes, especially when the action of hazardous events (e.g., earthquakes) can mine their structural stability and, subsequently, the stored material. In this view, a robust and reliable design approach is crucial for civil engineering professionals, which need to properly understand and predict the dynamic conditions to which silos are subjected, especially under seismic excitations. The current European standard, EN 1998-4-2006, employs a static approach using equivalent loads to simulate the additional hydrodynamic seismic pressure. However, a more realistic estimation of additional seismic overpressure could yield a more rational steel wall analysis and design for new structures and assessment for existing structures. To this end, this paper presents detailed numerical analyses to estimate the dynamic overpressure experienced by silos wall under seismic excitation. In detail, finite element models were created for two geometries of silos, i.e., slender and squat, and nonlinear time history analyses were carried out. The detailed models accounted for geometrical and mechanical nonlinearity of steel silos and of stored granularlike solid material. This latter was simulated by employing hypoplasticity as constitutive model. The output of the analyses allowed to quantify the additional dynamic pressure, which was compared to the one provided by the European standards (i.e., equivalent static approach). The comparison highlighted significant differences, underscoring the need to revise the current code-based approach.