Continue to Site

Eng-Tips is the largest engineering community on the Internet

Intelligent Work Forums for Engineering Professionals

  • Congratulations The Obturator on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

Modelling a simple flat footing in Abaqus

Status
Not open for further replies.

ac82

Civil/Environmental
Mar 9, 2012
1
I am a naivete in Abaqus. I am trying to do my thesis on Behaviour of Shell foundations by modelling it in abaqus. Since its an isolated footing it is a 3D analysis. I haven't yet succeeded in getting a successful run yet even after a lot of trials.
I am trying to validate the results from a paper bt Abdel rahman(1997).I started with a flat footing(concrete) of size 0.16m x0.16 m x 0.04m on soil medium (loose sand) of size (2.4m x 2.4m x 0.64m). The analysis using just elasticity parameter worked fine. But when plasticity parameters were added it aborted with these warnings and errors.

All of my analysis have aborted so far with warnings and errors like the following:

***WARNING: THERE IS ZERO FORCE EVERYWHERE IN THE MODEL BASED ON THE DEFAULT
CRITERION. PLEASE CHECK THE VALUE OF THE AVERAGE FORCE DURING THE
CURRENT ITERATION TO VERIFY THAT THE FORCE IS SMALL ENOUGH TO BE
TREATED AS ZERO. IF NOT, PLEASE USE THE SOLUTION CONTROLS TO RESET
THE CRITERION FOR ZERO FORCE.

***WARNING: SOLVER PROBLEM. NUMERICAL SINGULARITY WHEN PROCESSING NODE
FOOTING-1.46 D.O.F. 1 RATIO = 2.87808E+12.


***WARNING: SOLVER PROBLEM. NUMERICAL SINGULARITY WHEN PROCESSING NODE
FOOTING-1.11 D.O.F. 1 RATIO = 39.3923E+12 .


***WARNING: SOLVER PROBLEM. NUMERICAL SINGULARITY WHEN PROCESSING NODE
FOOTING-1.11 D.O.F. 2 RATIO = 16.3919E+12 .

MAX. PENETRATION ERROR 3.08631E-09 AT NODE SOIL-1.4915 OF CONTACT PAIR
(ASSEMBLY_SURF-2,ASSEMBLY_SURF-1)
MAX. CONTACT FORCE ERROR 28.4554E-06 AT NODE SOIL-1.4213 OF CONTACT PAIR
(ASSEMBLY_SURF-2,ASSEMBLY_SURF-1)
PENETRATION ERROR TOO LARGE COMPARED TO DISPLACEMENT INCREMENT

***WARNING: THE SYSTEM MATRIX HAS 3 NEGATIVE EIGENVALUES.

IN AN EIGENVALUE EXTRACTION STEP THE NUMBER OF NEGATIVE EIGENVALUES IS
EQUAL TO THE NUMBER OF EIGENVALUES BELOW THE CURRENT SHIFT POINT.
THIS MAY BE USED TO CHECK THAT EIGENVALUES HAVE NOT BEEN MISSED.
NOTE: THE LANCZOS EIGENSOLVER APPLIES AN INTERNAL SHIFT WHICH WILL
RESULT IN NEGATIVE EIGENVALUES.

IN A DIRECT-SOLUTION STEADY-STATE DYNAMIC ANALYSIS, NEGATIVE
EIGENVALUES ARE EXPECTED. A STATIC ANALYSIS CAN BE USED TO VERIFY THAT THE SYSTEM IS STABLE.

IN OTHER CASES, NEGATIVE EIGENVALUES MEAN THAT THE SYSTEM MATRIX IS NOT
POSITIVE DEFINITE:
FOR EXAMPLE, A BIFURCATION (BUCKLING) LOAD MAY HAVE BEEN EXCEEDED.

NEGATIVE EIGENVALUES MAY ALSO OCCUR IF QUADRATIC ELEMENTS ARE
USED TO DEFINE CONTACT SURFACES.


29 SEVERE DISCONTINUITIES OCCURRED DURING THIS ITERATION.
10 POINTS CHANGED FROM OPEN TO CLOSED
9 POINTS CHANGED FROM CLOSED TO OPEN
10 POINTS CHANGED FROM STICKING TO SLIPPING


And finally with this error the analysis aborted

Too many attempts made for this increment

Abaqus/Standard Analysis exited with an error - Please see the message file for possible error messages if the file exists.

Any help is most welcome and eagerly awaited!!

Thanks in advance!!

 
Replies continue below

Recommended for you

Don't worry about Abaqus; focus on the FEM. Numerical singularity means that some thing is free to fly away and it needs to be properly constrained.

*********************************************************
Are you new to this forum? If so, please read these FAQs:

 
Status
Not open for further replies.

Part and Inventory Search

Sponsor