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[SEAOC] MATS, etc. Software

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An important consideration when evaluating software for mat foundation
analysis is whether the finite element used is a THICK plate/shell element.
In other words, does it accurately model out of plane (transverse) shear. 

The MATS program actually uses a THIN plate element(!), which may cause
serious accuracy problems. Be sure that the program you're looking at does
use an element that accurately models transverse shear; otherwise your
results may be meaningless.

GTSTRUDL, SAP90, SAFE and RISA-3D are some examples of programs with THICK
plate/shell elements that accurately model transverse shear and thus are well
suited for mat foundation analysis. The VisualAnalysis program mentioned in a
prior posting uses a THIN plate formulation. I'm not familiar with the
AnalysisGroup product (from the same company as VisualAnalysis), so I don't
know what element they use in that product.

Here's a simple test problem you can use to test a plate element for
tranverse shear accuracy. Imagine a simply supported 10' beam with a 3'x3'
cross section. Model this using a 10x3 grid of plate elements. This gives you
a mesh of 1'x1' elements 3' thick (a very thick element). Apply a surface
load of 1k/ft**2 to the plates. Now check the total shear at a distance of 6"
from the support edge. This would be the center point for the three elements
at the end. This shear should sum to 13.5 K.

Bruce Bates

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