Robot Structural Analysis Forum
Welcome to Autodesk’s Robot Structural Analysis Forums. Share your knowledge, ask questions, and explore popular Robot Structural Analysis topics.
cancel
Showing results for 
Show  only  | Search instead for 
Did you mean: 

RC member required reinforcement calculation positions

15 REPLIES 15
SOLVED
Reply
Message 1 of 16
Mirko.Jurcevic
1211 Views, 15 Replies

RC member required reinforcement calculation positions

I have very simple frame model. See attached image.

I am trying to get required reinforcement in the beam.

My problem is those points (calculation position) in 0,40 and 4,60m. Beam span is 5m.

No matter how I adjust beam division, Robot always starts calculation in 0,40 an 4,60m points. Is there a way to change this?

The problem is in fact that I have negative bending moment in the begining of a beam, and Robot sometimes gives me 0 reinforcement in 0,40m when it should be something because of the moment at the start and end of a beam.

If this solved your issue, please Accept it as Solution help other forum users with similar issues to find answers easily.
  
Mirko Jurcevic


My blog: www.engipedia.com
Try my Revit add-ins: Autodesk App Store
15 REPLIES 15
Message 2 of 16

Try a different setting here

 

support width.PNG

 

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
Message 3 of 16

Hi

 

Try to change the parameters in the member type definition dialog. Under beam tab, choose Span length in axes option.

Message 4 of 16

Yes, that was the problem, it works now. Thank you both!  🙂

Interesting thing is that I knew that it has to do something with support width or something like that, but I just couldn't remember where.. Smiley Embarassed

 

I've put left and right support width to 0,0 so I can get reinforcement in the beginning and in the end of the beam and I noticed this:

When I put "Calculate beam in every 0,2m" it calculate beam in all n*0,2m but not in 5,00m (which is my span length).

When I put, for example every "0,25" I get calculation in 5,0, also for every "0,1m" but not for 0,20m!

For 0,33m works as expected.

Here are few screenshots:

for 0,20m

for 0,25m

for 0,33m

 

Question is, shouldn't we have a "5,00m" point when we put "0,2m" division?

 

And also, when I choose option "divide into n points" it works ok (in 0m and in 5m)!

If this solved your issue, please Accept it as Solution help other forum users with similar issues to find answers easily.
  
Mirko Jurcevic


My blog: www.engipedia.com
Try my Revit add-ins: Autodesk App Store
Message 5 of 16

Attach the model please.



Artur Kosakowski
Message 6 of 16

Hi

 

In my model, the same thing is happening. I wonder if the last segment isn't considered in 0.33 or 0.1. Becasewith respect to 0.2 and 0.25 the segments are correct.

Message 7 of 16

I'm not sure if I understand what you mean without having a chance to look at the model. Anyway try to replace the every 0.33 m with the corresponding number of divisions. For beam that have spans different then n*0.33 m this may actually be a better choice Smiley Happy



Artur Kosakowski
Message 8 of 16

Hi

 

I'm not sure if I understand what you mean without having a chance to look at the model.

 


In my post I wrote:

In my model , the same thing is happening.

 

I suppose you are not reading the posts carefully, Artur & Rafal. Please read the posts carefully.

Message 9 of 16

Yesterday, I had a day off.

I am attaching my model, please try to investigate.

If this solved your issue, please Accept it as Solution help other forum users with similar issues to find answers easily.
  
Mirko Jurcevic


My blog: www.engipedia.com
Try my Revit add-ins: Autodesk App Store
Message 10 of 16

Hi Mirko,

 

As you may expect this is due to numerical precision of mathematical operations on numbers and if you set 0.199999 the value at 5.0m will be shown. I have suggested the development team to modify the approach and run calculations in the 'last' point of the beam regardless of the value entered in the spacing field (which means that even for 0.33m the check at 5.0m would be done as well).

 

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
Message 11 of 16


HoshangMustafa wrote:

 

In my post I wrote:

In my model , the same thing is happening.

 

I suppose you are not reading the posts carefully, Artur & Rafal. Please read the posts carefully.

In your description you wrote:

 

In my model, the same thing is happening. I wonder if the last segment isn't considered in 0.33 or 0.1. Becasewith respect to 0.2 and 0.25 the segments are correct.

 

The situation described by Mirko is that for certain spacing the last calculation point, which is exactly the beam's end is not shown in the reinforcement table. E.g. in his case it is at 5m and he checked spacing 0.2m (25*0.2=5) and 0.25m (20*0.25=5).

 

Following your description I would assume that your beam has got the length which can be divided by 0.2 and 0.25 to create segments of the same lengths. If yes, then if you divide the entire beam into parts with 0.33m of lengths the last segment has to be shorter than 0.33m which means the very end of the beam is in this situation correctly disregarded. That is why I was not sure what kind of the issue you actually encountered. All I can say is that the more precise description you provide the easier it is to understand. Thank you.

 

 



Artur Kosakowski
Message 12 of 16

Yes, I've also tried to do the calculation with 0,19999999 and that way I get calculation in the last point as I assumed that it has something to do with number rounding, precision or something.

But, I can't figure it out how exactly it does that. That's not such a big problem because we can divide beam into N parts and get satisfying result with calculated first and last point. Example: beam with 5m span, we divide it into 26 points and it is equal to 0,20m long divisions. No problem here.

 

What I don't understand is why it works well with 0,25m long division (among others: 1,0m; 0,5m; 0,1m; 0,05m etc.), and only for 0,20m don't,

example, with 5m span:

500/25 = 20 segments -> 21 points

500/20 = 25 segments -> 26 points

both divisions are integers, for either number it should work for the last point as well.

 

What Robot does:

500/25 = 21 points Correct!

500/20 = 25 points Wrong!

 

I would dare to say that I think this is a insidious bug.

If this solved your issue, please Accept it as Solution help other forum users with similar issues to find answers easily.
  
Mirko Jurcevic


My blog: www.engipedia.com
Try my Revit add-ins: Autodesk App Store
Message 13 of 16

It is the 'precision' of changing numbers between binary and decimal systems. In other words you may say that Excel cannot sum up correctly. 



Artur Kosakowski
Message 14 of 16

I must admit that I wasn't aware of this error.

Interesting.. Smiley Happy

 

Thanks for the explanation!

If this solved your issue, please Accept it as Solution help other forum users with similar issues to find answers easily.
  
Mirko Jurcevic


My blog: www.engipedia.com
Try my Revit add-ins: Autodesk App Store
Message 15 of 16

Improved in SP4 for Robot 2015.



Artur Kosakowski
Message 16 of 16

Can't find what you're looking for? Ask the community or share your knowledge.

Post to forums  

Autodesk Design & Make Report