Efficient beam-column finite element including application to thermoelastic deformation

Abstract

During the study of the structural design of the core of the Gas Cooled Fast Reactor (GCFR), there is evidence of undue frictional interaction between fuel rod claddings and their spacer grids. In cases for which thermal bowing of the rods is sufficient to cause two-sided contact between the rods and their supporting grids (and thus a tendency to lock up), subsequent rod deformation caused by the axial thermal expansion would result in excessive buckling of the rods between locked supports. The numerical solution is best served by the finite element method. Yet there is a large number of fuel rods in the reactor, of which each is multiply-supported by spacers. Hence, an efficient finite element is needed that would model each section between supports with not more than three elements. The new efficient finite element is developed, beginning with the principle of virtual work.