Seismic Assessment of Horizontal Cylindrical Reservoirs

Abstract

Industrial facilities contain a large number of constructions and structural components. Both building and non-building structures typically can be found in an industrial/chemical plant. Above ground pressurised tanks are typical examples of non-building structures of such sites. These equipment are typically used for the storage of gas and liquid materials, e.g. chlorium, ammonia etc. The overall design of such structures, especially in low to moderate seismicity areas, has neglected any seismic loading in the past, basically due to the absence of relevant seismic requirements in previous codes. The seismic security of above ground pressurised tanks is of great importance, since failure of these structures can lead to negative impact for the environment and to economic losses. Recent codes for seismic design and construction of horizontal cylindrical reservoirs provide tools which can serve also to assess existing tanks. From experience, the seismic deficiencies of reservoirs of this type are in general concentrated in some strategic points. This paper describes the main deficiencies of such structures and the simplified methodology used for their assessment based on the guidelines presented in Eurocode 8. In addition, typical cost effective solutions for the retrofit of the tanks with these shortcomings are presented and critically discussed. The above assessment and retrofit methodology is illustrated for some examples of typical equipment.