HYBRID-TREFFTZ PARA-METHOD ELEMENTS FOR ANALYSIS OF FLAT SLABS WITH DROPS

A simple method is presented by which various types of internal displacement fields involved in the Hybrid-Trefftz (HT) element formulation for flat slabs with drops can be generated in a unified way. Apart from a standard set of displacement functions for an isotropic plate element, such fields involve, in particular, a special purpose set of functions representing the local solution in the vicinity of a column. The elastic properties of the column and the effect of the sharp radial variation of the plate thickness in the drop area are properly accounted for. The presented functions extend the library of optional internal displacement fields with which an advanced HT element subroutine is typically provided. Its use along with the p-extension of the HT elements enables the local effects in flat slabs with or without drops to be efficiently handled through crude unrefined finite element meshes by using just a single element for each column head as well as a large portion of the surrounding slab. The accuracy and the practical efficiency of the approach are assessed on a series of numerical examples involving a comparison with a three-dimensional analysis.