Variable node plate bending element for mat foundation analysis

Abstract The variable node plate bending element, i.e. an element with one or two additional mid-side nodes is used effectively in the analysis of a mat foundation. The variable node elements can generate a nearly ideal grid for mat foundation analysis in which more nodes are defined near the column location where the steep stress gradient is expected. The plate bending element used in this study is based on Mindlin/Reissner plate theory with substitute shear strain field. The nodal stresses of that element are obtained by local smoothing. The interaction between the soil and the mat foundation is modelled with Winkler springs connected to nodal points in the mat model. The vertical stiffness of the soil material is represented in terms of a modulus of subgrade reaction and is computed in a similar way to the computation of consistent nodal force of uniform surface loading. Several mesh schemes were proposed and tested in order to find the most suitable scheme for mat foundation analysis.