THE IMPROVEMENT OF THE SEISMIC VULNERABILITY OF STEEL STORAGE TANKS WITH SLIDING ISOLATORS

The improvement of the seismic performance of industrial plants represents a fundamental need to guarantee the environmental and life safety of the area surrounding the plant. The industrial facilities that are working, for example, in the chemical or the petrochemical fields, usually have large steel storage tanks, which recent post-seismic surveys have observed can suffer several damages such as the elephant-foot-buckling, the uplift or the complete instability with the overturning of the structure. Such structural damage can cause the plant's shutdown, reducing the local infrastructure's resilience, or even large dispersions of the content in the environment, with adverse effects on human safety and the ecosystem. Due to the uncertainties related to the estimation of the mechanical properties of filled tanks and related seismic loads (i.e., dynamic overpressures generated by the content), conventional design approaches may lead to unsafe or, on the contrary, oversized solutions. The base isolation through Curved Surface Sliders isolators (CSSs) has been adopted in different structures, and the use of such a system for steel storage tank applications is not wide to the difficulties in the design process. The present paper discusses a study on the influence of base isolation with CSSs to highlight the valuable advantages in terms of the improvement of the seismic vulnerability of steel storage tanks. Furthermore, the initial peak of friction force at CSSs' motions breakaway modifies the overall response of the isolated system. Within this framework in this study, a parametric investigation through a numerical model developed in OpenSees FEM code is carried out to compare the effect of the breakaway and different materials in the CSSs on isolated tanks providing useful insights for the selection of the most suitable device.