Vessels in high seismic zones are subjected to lateral forces during earthquakes that cause large stresses in the vessel wall. Section 100 of the Civil and Structural Manual also presents methods and examples for calculating the magnitude of seismic loads and their effect in vessel design.
The following information is required to consider the effect of earthquakes on the design of the vessel:
• Seismic zone at the facility
• Height or length and wall thicknesses of the wall
• Weight distribution along length of vessel
• Type of support system
• Site coefficient, which is a function of soil type
• Operating weights of vessel (both pre-service and in-service)
• Weight of attachments and their location.
The seismic zone and description of site coefficients for typical Company facilities are given in Section 100 of the Civil and Structural Manual. Using this information and following the procedure and examples, the forces of earthquake loads on the vessel and its supports can be calculated. The critical moment is the larger of the two moments for wind or seismic loadings.
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