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Version 2.5.4 (Released at 07/14/2019)
- Vietnamese language has been added to the program.


Shallow foundation problem(Read 196 times)
Shallow foundation problem on: August 03, 2019, 04:35:30 am
Hi:

I am new to ADONIS... and also new to finite element method :-[.

I try to make a very simple model for the analysis of a shallow foundation (strip footing). Everything works correctly when I establish an elastic linear model, but things get twisted when I use an elasto-plastic model (Mohr-Coulomb).

I attach a script to generate the geometry, boundary conditions, load and material definition, solve the model and plot y-displacements. One using linear elastic (shallow_le.ajs), another using mohr-coulomb (shallow_mc.ajs).

Can someone give me a hand? I'm sure I'm doing something wrong.

Thank you.



Re: Shallow foundation problem Reply #1 on: August 03, 2019, 10:51:21 am
MC is a nonlinear constitutive model (i.e. elasto-plastic). so if the applied load to the system is greater than the strength of material, model is going to fail (or go plastic) and consequently equilibrium is not going to be reached. it seems like your model has similar situation. if you increase the shear strength you will see that eventually model is going to converge but still in elasto-plastic zone. for example I increased cohesion to 10 kpa and as a result model converged as you can see in attached script file.

I highly recommend you to read famous book titled "Geotechnical Modelling" by "David Muir Wood" to understand the concept behind the constitutive models.

one more thing, since gravity is not activated the amount of "density" has no effect in your model but for the future reference you have to make sure you use kg/m3 as unit of density for "stress-pa" and 10e3 x kg/m3 for "stress-pa". for instant if you have 1900 kg/m3 density for "stress-pa" you should use 1.9 for "stress-kpa". by the way it's "density" not "unit weight" detail system of units are given in the manual.

-Roozbeh



Re: Shallow foundation problem Reply #2 on: August 04, 2019, 11:10:39 pm
Thank you very much for your reply.

I will continue working with the script you attach and the book you recommend.

A greeting.