FRAGILITY CURVES FOR STEEL INDUSTRIAL SILOS ACCOUNTING FOR FILLING LEVEL OF GRANULAR-LIKE MATERIAL

This study presents an assessment on the seismic fragility of ground-supported steel silos storing solids. As key units in the different industrial sites, storage systems are crucial for the proper and continuous functionality of the relevant industrial operations that can be intended for vital activities such as the food supply. Nevertheless, it is undeniable that storage systems are more vulnerable to seismic events than other units as evidenced in the past. In this context, this work aims to estimate the seismic fragility of ground-supported steel silos, which represent a very common form of storage systems containing granular material. The effect of key factors, such as the silo geometry and the absence/existence of the filling material, which significantly affect the seismic behavior of silos was addressed. In addition, the governing damage patterns is determined. To achieve these goals, two different silos with different distinctive geometries (slender and squat) were investigated considering the empty case and the 90%-filled case. First, a detailed numerical model was built for the investigated cases by using finite element software ABAQUS. After a phase of model validation, the dynamic properties of the silos under investigation were assessed through eigenvalue analysis, while the seismic buckling capacity of the different silos were evaluated through nonlinear static and time-history analysis. Finally, fragility curves of silos were derived by identifying the most critical buckling capacity corresponding to the specific damage patterns, showing the influence of each parameter on the seismic vulnerability and behavior of these kinds of structures.