Warning Message 2

[mpirez]

Hi! Evertyime I run a model I get the following warning:
"***WARNING*** THE SOLUTION LOST 6.7 DIGITS OF ACCURACY FOR DOF UZ OF JOINT 11484 LOCATED AT X = 1414.000, Y = 698.444444, Z = 1056.000, STIFFNESS MATRIX DIAGONAL VALUE = 2.6116E+10"
Why does this happen? What can I do to prevent this error?
Thanks in advance,
Monica

 

[amadeus]

Normally, this warning messages dissapear when you mesh the shell elements into smaller pieces. Try reducing the size of the mesh elements and that error will probably go away.

Amadeus

 

[fafaf]

I would suggest that you check the displacements of the structure (on the display, and animating the displacement graph in 3d makes it easier finding the members making very large displacements) and find very large displacement.
The remedy is to introduce more restraints or connect the offending member.

I hope this helps,

 

[andiron]

amadeus:
just getting a hang of etabs 8.2.7..and was trying with various ways of modelling slab/shear wall/wind etc..

if one area is drawn for the whole floor (bldg has columns and c shaped shear walls ) and auto mesh area into structure is cliecked (with say 4'X4' meshing enforecd) and voila! etabs does it..as per mr habibulla you can enforce auto-line constrain and not worry about meshing not being compatible in the tradional sense..in fact as per habibulla the shell stress contour may jump across elements but largely ok..so far so good..but analysis will often yield some error due to, in my opinion, this "fudgy" meshing..

i tried inpputing random columns, with no walls, and did auto meshing and the program did not even acknowledge if some columns where there.. irritated, i did bay-by-bay auto meshing by manually drawing null lines connecting the columns and meshing looks much better..i merged all the areas to make one diaphragm..results seem much better on that..
so the auto meshing isn't really auto..and meshing by the progrem is still quite often not correct...

tell me what you think about it..

ths andiron

 

[andiron]

amadeus is WRONG!!!

 

[Murali27]

I think that when the stiffness value is in the order of +10e6 or more, no need to worry about this.

You can check gloabl force envelope to see the percentage of error in loading.

I can see this certainly meshing problem.