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Stability of Block Structures

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cfporst

Structural
May 28, 2014
7
I've been modeling structures made of discrete blocks (parts) in 2D such as arches, a Roman aquaduct, and a flying buttress and then applying gravity loads on the whole models. I've been "tilting" the models by using trigonometry and applying the appropriate portion of gravity load in the X and Y directions in order to simulate levels of tilt until the model can't run (becomes unstable).

The problem I'm having is with the flying buttress I can't make the model run with any level of friction 'Penalty' in the contact between the blocks so I used the 'Rough' tangential interaction property. With this I am able to run the model with purely vertical load (no tilt) but when I apply any gravity load in the X direction, no matter how small, the job aborts. Can anyone help tell me why this is?

Attached is a picture of the results of the vertical gravity load with the 'Rough' contact definition. As you can see there is an acute stress concentration between the bottom of the top most arch block and the adjacent column block. I think this is why I can't run it with any level of friction 'Penalty'.

Thanks.
 
 http://files.engineering.com/getfile.aspx?folder=daf1184a-48cc-41eb-a8db-4cc859287b71&file=Discrete_Vertical.JPG
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I see, it is a Static Analysis with a Linear Direct Sparse Equation solver.
 
Could the problem be that you do not have sufficient compression in the buttress (strut) which causes tensile stresses in the section. With no-tension conditions between the blocks and your 'column' on the right hand side bending (is there no symmetry or constraints for it not to bend to the right) it is not clear how can you achieve equilibrium.
 
Also, it is Abaqus/Standard. Therefore it is Implicit
 
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