Seismic vulnerability of horizontal cylindrical tanks in industrial facilities

The purpose of this study is the development of vulnerability curves for a generic industrial facility steel frame, considering the presence of a non-structural element (horizontal cylindrical tank). A simplified procedure to model a generic tank as single degree of freedom systems is illustrated and the calculation of the seismic shear force at the base of the tank is made. In order to evaluate the seismic behaviour of the tank-structure system two different seismic analyses have been conducted and the results compared. Then, the methodology for the development of the fragility curve is illustrated. Specifically, for the study case, a series of nonlinear dynamic analyses are carried out assuming as variable parameters the level of the intensity measure, in terms of Peak Ground Acceleration, and two different properties for the material of the primary structure. The shear force for the tank and the interstorey drift for the structure are assumed as damage measure for the construction of the fragility functions. At the end, a brief overview of the concept of resilience is presented, with the focus on the process to obtain the vulnerability curves in terms of direct economic losses from the fragility curves, once different limit states are defined