Analysis of vessels' supporting skirts for shear transmitted by bearing

Vertical vessels are sometimes supported by means of suitable structure resting on a reinforced concrete foundation (pedestal). This support structure between the vessel and the foundation may consist of an integral (or welded to the vessel) cylindrical shell termed a 'skirt'. Reactor pressure vessels or Steam Generators can be subjected to very high lateral external loads during a seismic event or due to a loss of coolant (LOCA). These loads have to be transmitted to the foundation via the skirt. One way of transmitting the applied shear load is by direct bearing between the skirt bearing flange and a ring bumper around and in contact with the skirt flange and securely attached to the concrete foundation. Due to this mode of shear load transfer the skirt bearing flange and part of the shell in its vicinity will be subjected to stresses which need to be evaluated. A model has been devised in which the bumper was idealized as a set of linear springs which can take only compressive loads. The problem was solved by iteration, where convergence was quick and uniform. (Auth.)