Analyzing Mat Foundations using STAAD.Pro

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It is best to use the PLATE MAT command if the surface is modeled using plates. The PLATE MAT command is superior to the ELASTIC MAT command in terms of its ability to accurately determine the influence area of nodes for the support generation process. The ELASTIC MAT command is very sensitive to tolerances, and minor distortions in terms of precision of coordinates of the nodes which are supposed to make an edge straight.

However, please note that the PLATE MAT command can be used only if the mat surface is modelled using plates. If it is modelled using beams or solids, you will have to use the ELASTIC MAT command, because, without plates, the PLATE MAT facility won't be able to determine the influence area of the nodes. You ought to strictly adhere to the rules explained under the "Notes" heading in Section 5.27.3 of the Technical Reference Manual when using the ELASTIC MAT.

What is the difference between using a plate mat vs an elastic mat? Is one better that the other? I have a 90'h x 28'w x 85'l fully-enclosed building, with a 3' deep mat foundation.

This document has been created by Kris Sathia of the Bentley Technical Support Group. It provides answers to questions on the aspects one must consider when analyzing mat foundations for different types of load cases.