I have to perform an analysis of a cube with the 20_8_BrickUP elements and the PressureDependMultiYield02 material.
The cube is divided by 335 element, the lateral surfaces are pinned and the only x displacements are free.
The top surface is fixed in water pressure only (put equal to 1 the IV dim.). The bottom is fixed with the only x displacements free.
Basically I'm following the developement steps of the openseespy doc in the GeoExample paragraph referring to the SiteResponse3D analysis case.
The particularity of my case is that I have some good results in pore pressure and displacements until the last but one step, in the very last plastic step the results go crazy instead.
Both elastic and plastic analysis converge.
I didn't find an openseespy visualizer for the 20 8 BrickUP element, so I used the GidConverter flaviaWriter.m file considering 8 nodes only.
Why in the very last step the results plotted go crazy ?
The analysis step for the gravity loading stage is composed in this way:
ops.model("basicBuilder","-ndm",3,"-ndf",4)
# update materials to ensure elastic behavior
ops.updateMaterialStage('-material', 1, '-stage', 0)
ops.updateMaterialStage('-material', 2, '-stage', 0)
ops.constraints('Penalty', 1.0E14, 1.0E14)
ops.test('NormDispIncr', 1e-6, 100, 1)
ops.algorithm('Newton')
ops.numberer('Plain')
ops.system('ProfileSPD')
ops.integrator('Newmark', gamma, beta)
ops.analysis('Transient')
startT = tt.time()
ops.analyze(20, 500)
# update material to consider elastoplastic behavior
ops.updateMaterialStage('-material', 1, '-stage', 1)
ops.updateMaterialStage('-material', 2, '-stage', 1)
ops.analyze(80, 0.001)
The last but one displacement results:
The very last step displacement results:
(the images represent the pore pressure results in deformed mesh)
thank you for your attention.