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## Robot Structural Analysis

Mentor
Posts: 171
Registered: ‎01-24-2009

# Erratic values in RC design module with ICK ?

172 Views, 4 Replies
02-14-2012 09:52 AM

Hi All,

Using ICK with SP5 we are getting values that seem not coherent. As shown in the pictures we have tested values related to a beam in a model (I.e.. Beam ° 39)

Step 1: we have calculated the structure and verified the bending moments. The envelope of moments of RC module was getting two value of -443.40  for the moment of the beam n. 39 on the Left Node as shown in the picture.

after this we have checked the coherence of the stresses acting on the beam in the RC design module with the values in the model. From the confrontation the values is evident a big difference among values. In no case for the selected beam we have a moment bigger than the value used in the RC design module. The maximum value of the moment is for the beam is -305 !!!

We have then created the manual combination from the automatically generated one and then we have passed to RC module and ... The maximum moment changes !!! As shown in the picture. -251.86 versus -443.40

Finally we have checked the new values with the envelope and, in this case, the moment value seems coherent (the different value is due to the evaluation of the moment at net span.

I really hope I am wrong.

Thanks

Product Support
Posts: 5,046
Registered: ‎12-17-2010

# Re: Erratic values in RC design module with ICK ?

02-15-2012 02:37 AM in reply to: GabrieleNovembri1027

Gabriele,

My understanding is that in the first example you:

1. Defined the model and loads

2. Created either manual or automatic combinations

3. Calculated the model and checked results

4. Selected the beam and imported simple cases allowing the RC beam module to generate combinations

In the second example

1. Defined the model and loads

2. Created manual combinations

3. Calculated the model and checked results

4. Selected the beam and imported combinations so that they are used in RC beam module

My assumption is that the combinations generated inside the Rc Beam design module after importing of simple cases are generated in the different way than these in the model.

Assuming that you created in the model the load combinations you want to use in the design I would say import them. This is why the import of combination option has been created for

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

Artur Kosakowski
Mentor
Posts: 171
Registered: ‎01-24-2009

# Re: Erratic values in RC design module with ICK ?

02-15-2012 05:18 AM in reply to: Artur.Kosakowski

Hi Artur,

Unfortunately I cannot agree with you for the following reasons:

1. Regardless of the workflow I am using to design the reinforcement it seems to me quite obvious that the result must be the same (combination generated in the RC design module or imported combinations). In both case given that I am using the same regulation the combination (generated or imported) should be the same. I cannot imagine you are arguing that the reinforcement of a RC structure depend on the workflow I can adopt.  The logical conclusion is that there are two regulations implemented (one in the main program and the other in the RC module) one of which is wrong.  The interesting question is which is the Wrong one ?  The actions calculated in the main program or the action calculated in the RC module ?   I must emphasize that Robot is used by structural engineers that design structures that may collapse. You don't believe that this situation is dangerous ?. Anyway let me know  if possible, which are the wrong actions: The actions calculated in the main program or in the RC module ?
2. We are using a default option given by the software. The reason is quite simple: with several hundreds of load combinations with the imported combination the RC module take about 15 minutes to design a four span beam. If you have, as in my situation 2741 beam considering an average of four span I will spend about a month the design all the beams.

Thanks

Product Support
Posts: 5,046
Registered: ‎12-17-2010

# Re: Erratic values in RC design module with ICK ?

02-15-2012 06:08 AM in reply to: GabrieleNovembri1027

Gabriele,

Please mind that it is you who have the model and know what settings you set (regulations (e.g. I don't know if they are the same for the model and the design module), design code selections, way of importing loads etc. ). All I can do is to guess what the possible reason for the difference you described could be having set of pictures and your description without the access to the model itself. Trying to help you I'm not  in the position to judge the situation without having the complete set of information and my intention is to find the workable solution which I think is the priority for the forum (all I'm trying to do is to help you in the best way I'm able to). According to my knowledge the results when you use the same regulation should be the same for both method but there may be some issue that I'm not aware of and which requires our attention.

If you think that you found some error in the program please report it creating the service request from the Subscription Center (or if you prefer I can create it on your behalf) especially for situations that require deeper investigation. Thank you for your understanding and help.

Artur Kosakowski
Mentor
Posts: 171
Registered: ‎01-24-2009

# Re: Erratic values in RC design module with ICK ?

02-16-2012 04:39 AM in reply to: Artur.Kosakowski

Hello Artur,
Thanks for your interest. I understand your difficulty to verify the situation without the model and all parameters.
I did some tests and I could not regenerate the error in a new model. I assume that there is something in the model getting the error  that causes the a different behavior with manual or automatic combinations.
Since the model is very big I will try to isolate one part that reproduces the same error and send it through support.

Thanks