Procedure 4-2 Seismic Design - General

Pressure vessels and their supports must be designed to resist the forees and loadings anticipated during a seismic event... an earthquake. The seismic design is not defined by the ASME Code but by building codes (previously NBC, SBC, and UBC, but now IBC) that reference technical standards such as ASCE/SEI 7, ACI 318, and AISC 360. Many countries have their own seismic standards and there are international standards as well. The ASME Code states in UG-22 that the vessel and support structure must be designed to withstand the forces from a seismic event. 

A seismic event causes the vessel to sway as a result of the ground motion. How much loading the vessel experiences is dependent on the type of foundation and supports, the size and proportions of the vessel, the geographic location of the vessel, and the 

Additionally, the site class has an effect on the design loadings. In general, site classes comprised of hard rock will have less intense shaking than site classes composed of soft soils. 

Seismic design procedures can be accomplished for most vessels by one of the two methods as follows  

Seismic design criteria may provide linear and nonlinear seismic response history procedures, but these are not as commonly used for vessels. 

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The decision to install monitoring instrumentation and to safety classify it is usually taken on the basis of the relevance of the external event hazard for system design and, in general, on the basis of the instrumentation s significance for the plant s emergency procedures. Seismic monitoring and automatic scram systems, when installed, need to be properly classified for safety and adequate redundancy according to their objectives. 

Based on limited observations made above, it appears that approximate Incremental Response Spectrum Analysis (IRSA) procedure, which is the natural extension of the traditional Response Spectrum Analysis (RSA), proves to be a reliable analysis tool for deformation-based seismic assessment and design of bridges in the general framework of performance-based design. 

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