FAILURE MECHANISM IN NUMERICAL ANALYSIS


Dear Friends, 1) What is the exact meaning of failure in Numerical analysis? 2) In elastic analysis we look for overstressed zones is that means that the zone has failed and how to confirm it? If it has not failed how can I confirm what state of stress is existing there? 3) In plastic analysis we look for yielded zones is that means that the zone has failed and how to confirm it? If it has not failed how can I confirm what state of stress is existing there? 4) If failure exists in certain zones of the model how to confirm that the model is overall stable or not and how to confirm it? 5) What are the general procedures to check stability of models in numerical analysis? 6) In tunneling we find there are certain zones yielded around the tunnel periphery, how to check that in these zones high gradient stresses are occuring? Best Regards, Debasis

Software Deep Foundations Soil Mechanics / Geotechnical Computational Geomechanics Soil Mechanics / Geotechnical

Asked 30/06/2005 12:41, updated: 14/03/2017 14:07
Debasisbarman

1 Answer

Votes: 0

Johnjohn

Having a limited experience working with Abaqus/Nastran and open source programs: 1)Failure is when the program is not working 2)Always perform an elastic analysis before using a more complicated inelastic one. At the bottom line, your program is probably using the modified Newton Raphson method, which is a sequence of elastic analyses. The material cannot fail in an elastic analysis. You can confirm the state of stress simply by reading it from the program. 3)A yielding zone of material does not mean that your foundation/dam etc has failed. You can again confirm the state of stress simply by reading it from the program. 4)If the model is unstable, and you 're using the FE method, than you will see a mechanism appearing and the program will stop (with error messages), because the method cannot deal with it. Be careful because it may be the program's and not the method's fault! 5)Be careful: a foundation may be stable, but it may have settled a meter. To check the failure load of a foundation, you (may) perform multiple analyses, inreasing the foundation load. 6)Ask the program to give you the gradients. If it can do it graphically it is better.