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## Autodesk Simulation Mechanical and Multiphysics

Contributor
Posts: 16
Registered: ‎12-08-2011

# Problem with simulating concrete !!

284 Views, 11 Replies
12-24-2011 05:43 PM

hello to all of you

when i hit "run simulation", the analysis dialoge open up, after a while, it disapears suddenly, the log report tells me the following:

[ STOP: Perfect plasticity or compressive softening is not currently supported for concrete material ]

what does it means ?! ive got the concrete parameters defined well, and ready to go, what is the problem ?!

regards

Employee
Posts: 162
Registered: ‎10-04-2010

# Re: Problem with simulating concrete !!

12-24-2011 07:03 PM in reply to: 80DAVE

In the hardening curve, there are two neighboring points (for example, i and i+1), stress (i+1) is too close to or equal to stress (i) or smaller than stress (i).

Shoubing

Contributor
Posts: 16
Registered: ‎12-08-2011

# Re: Problem with simulating concrete !!

12-24-2011 11:18 PM in reply to: zhuangs

sadly, i've done what it takes to run the simulation, still getting this idiotic message !!

where can i get default values or something like that ?! i'm deseperetly need to run the simulation .!

Employee
Posts: 162
Registered: ‎10-04-2010

# Re: Problem with simulating concrete !!

12-25-2011 07:55 AM in reply to: 80DAVE

Did you check the hardening curve set up (see the attachment)?

Note that in the curve,  for each neighboring points i and i+1, [ stress(i+1)-stress(i) ] / [strain(i+1)-strain(i)] should not be too small (close to zero) or negative.

Shoubing

Contributor
Posts: 16
Registered: ‎12-08-2011

# Re: Problem with simulating concrete !!

12-27-2011 03:37 PM in reply to: zhuangs

i've used the following parameter:

mass desity (kg/cm3) = 0.0025

Young's modulus = 1.93466889634974E-03

Possion's ratio = 0.2

unaxial tensile strength (KN/cm2) = 2.54554439248869E-04

unaxial compression strength (KN/cm2) = 1.67059969203686E-03

biaxial compressive strength (KN?cm2) = 1.93789564276276E-03

shear retention is constant and the parameter is 0.2

Strain Vs. Stress curve

 0 0 -0.00026 -0.0005 -0.0006 -0.00104 -0.00095 -0.00141 -0.0013 -0.00161 -0.00173 -0.00167

i keep getting the following message

** STOP: Unable to determine concrete material constants (A4,K0) from specified concrete strengthes Check input or specify material constants directly Element group number = 1

please, what am i doing wrong ?! :'(

it's frustrating

Employee
Posts: 398
Registered: ‎05-06-2010

# Re: Problem with simulating concrete !!

12-27-2011 05:38 PM in reply to: 80DAVE

The following is from Help. Not sure if it's helpful or not.

Hardening Tab

The input on the Hardening tab are for the plain concrete. This input describes the stress-strain curve of the concrete in compression after the elastic region (points 2 to 1 in Figure 1).

Enter the Strain and Stress values as negative values, starting at the yield point (point 2). Using the Sort button will sort the values in descending order (yield point to failure point). A minimum of two data points are required.

The entries on the first row (Index 1) is the yield point and are linked to the Young's modulus entered on the General tab. Therefore, the strain for the first row cannot be entered; it will be calculated by the processor as (Stress row 1)/(Young's modulus). The interface will calculate and enter the strain for the first row if you try to select that cell; the processor will calculate the initial strain regardless of the value entered.

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Employee
Posts: 162
Registered: ‎10-04-2010

# Re: Problem with simulating concrete !!

12-27-2011 07:16 PM in reply to: 80DAVE

You might check whether the "Strength Tab" is well defined: Uniaxial Tensile Strength, Uniaxial Compressive Strength, Biaxial Compressive Strength, etc.  In the "Help", search "Reinforced Concrete Material Properties" and there is a figure "Figure 1: Idealized Uniaxial Behavior of Plain Concrete", which shows the different parameters.

Shoubing

Contributor
Posts: 16
Registered: ‎12-08-2011

# Re: Problem with simulating concrete !!

12-28-2011 12:51 AM in reply to: 80DAVE

dear Shoubing

i'm well aware of the "Idealized Uniaxial Behavior of Plain Concrete", my parameters are true, yet, cant start the analysis .!

it's very frustrated me and i'm running out of time !!

all the notes you've include, i'm familiar with it, those from the HELP and other notes, my parameters coincide with other software parameters, which yield to a successful modeling

why cant it be done on autodesk simulation ?!

Employee
Posts: 162
Registered: ‎10-04-2010

# Re: Problem with simulating concrete !!

12-28-2011 07:04 AM in reply to: 80DAVE

Is it the model large?  If not, you might share the model for us to investigate.  If it is large, you can share the model via dropbox.

Shoubing