What is GMNIA and why I like it so much?

GMNIA stands for Geometrically and Materially Nonlinear Analysis with Imperfections. It’s a fancy way of saying that this method looks at how structures behave under loads, considering both material and geometric changes. It also takes into account imperfections, which makes the analysis more realistic.

In simpler terms, GMNIA helps engineers figure out if a structure can handle the maximum loads without failing, by looking at both how the material might bend or break and how the shape of the structure might buckle.

And with same analysis, designer can off course plot the deformations regarding the nonlinear material model which produces much more realistic estimate compared to secant modulus approach.

Let’s see very simple structural member designed with hand calculation by Eurocode and SCI Design manual for structural stainless steel 4^th edition. This example is to illustrate the effects on sophisticated methods (nonlinear material model in this example) on service limit state deflections.

And how same thing looks through FEA with solid elements and nonlinear material model based on tested stress-strain data:

As we see from results, with even simple FE-analysis we can predict the structural behaviour much more accurately. In this case, the estimated deflection is almost 18% lower than with conservative hand calculations. There is very good chance that this may save you from unnecessary overdesign due to deflection limits!