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Message 1 of 17
HoshangMustafa
1097 Views, 16 Replies

Combined footing

Hi

 

Please find the attached file. In earlier posts I asked about combined footing and you gave me some guide. I appreaciate your answer (I could manage the situation according to your guidance). How about a combined footing between node 639 and 640 in the attached file? In my practice the combined footing will be rotated. How this is solved so that the combined footing would be parallel to global axes?

 

Another question:

 

After designing a combined footing, shouldn't the two nodes act as if they were linked by a rigid link? because if I design the combined footing I should remove the rigid link and the two substructures would be separated structures.

It will be more convinient, after designing a combined footing, the two nodes act as if they were linked by a rigid link.

16 REPLIES 16
Message 2 of 17

Please find the attached file. In earlier posts I asked about combined footing and you gave me some guide. I appreaciate your answer (I could manage the situation according to your guidance). How about a combined footing between node 639 and 640 in the attached file? In my practice the combined footing will be rotated. How this is solved so that the combined footing would be parallel to global axes?

 

No, but the columns should have the same orientation.

 

 

After designing a combined footing, shouldn't the two nodes act as if they were linked by a rigid link? because if I design the combined footing I should remove the rigid link and the two substructures would be separated structures.

It will be more convinient, after designing a combined footing, the two nodes act as if they were linked by a rigid link.

 

Mind that you already defined support under each of them which means that you alreeady determined how they 'behave' :smileywink:

 

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 17

Hi Artur

 

Mind that you already defined support under each of them which means that you alreeady determined how they 'behave' Smiley Wink

 

If I remove the supports, can the combined footing act as a rigid link between the two nodes?

Message 4 of 17

The presence of the supports is necessary for both preventing the structure from 'gonig down' under the applied load and for the export from a model to the RC Spread footing design module. If you want you can define a rigid link slightly above the nodes with defined supports.

 

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 5 of 17

Hi

 

It's more convinient for the combined footing (between two nodes in two substructures) take the same action as the rigid link. 

 

For clearity: I don't need a rigid link when modeling a mat foundation (containing two nodes of two substructures) as a panel.

 

I mean could the same thing be happen with a combined footing (not requiring a rigid link).

Message 6 of 17

I'm not sure if I understand you correctly but imagine a situation the the left column is under tension whereas the right one is under compression. Also if you defined supports in these nodes they are not supposed to move neither vertically nor horizontally unless you define them as elastic which usually is going to be for the vertical direction only (no horizontal movement allowed). For the elastic support the distance between the nodes can change which is not  posible for a rigid link. What rigid link analogy do you mean?

 

Anyway - setting the boundary conditions is in your hands. IMHO Robot offers you more than enough options to choose from Smiley Happy



Artur Kosakowski
Message 7 of 17

Hi

 

If I send you the file, can you make a combined footing between the two nodes 639 and 640? Node 639 is in substructure1. Node 640 is in substructure 2. In order to design a combined footing between the two nodes 639 & 640, I should remove the rigid link between them. If I remove this rigid link, the program will display (separate structures) message and would not design the combined footing between them. So what should I do?

Message 8 of 17

Attach the file.



Artur Kosakowski
Message 9 of 17

 

Hi

 

 

Please chech this link

http://we.tl/5RaIoMkUHD

Message 10 of 17

To run RC Design of a spread footing you have to have the support defined therefore both nodes have to be supported. In addition as I already exsplained the columns should have the same orientation (http://forums.autodesk.com/autodesk/attachments/autodesk/351/22129/1/orientation%20of%20columns.PNG) which is not the case in your model either. The possible solution is:

 

1. Delete the rigid link and define a support in node 640 so that both nodes have got supports assigned

2. Divide the columns creating a short bars (e.g. 10 cm) at their bottoms

3. Rotate these short bars as shown on the picture I indicated above

 

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 17

Hi

 

Thank you Artur

Please find the attached file. I followed your notes, it doesn't design the combined footing. I appreiate If you could design these the combined footing (@ nodes 639 & 640) and resend it back to me. Thanks in advance.

 

http://we.tl/YAH2NvnNpx

Message 12 of 17

My goal is to make sure that you are able to deal with such situations yourself rather than 'do the design' for you Smiley Happy

In short the idea is to:

 

1. Remove the rigid link

2. Define supports under both nodes

3. Divide columns and rotate their bottom parts so that the local X axes of these parts are pointing in the same direction

4. Calculate the model

5. Select both nodes and export them to the RC Spread Footing module answering yes for the two column foundation question.

 

Which of these points do you find difficult? 

 

 

 



Artur Kosakowski
Message 13 of 17

Hi

 

My goal is to make sure that you are able to deal with such situations yourself rather than 'do the design' for you :smileyhappy:

You can check the previous posts to know how much types of footings (single, combined, continuous, mat) are dealt by me.

 

In short the idea is to:

 

1. Remove the rigid link

2. Define supports under both nodes

3. Divide columns and rotate their bottom parts so that the local X axes of these parts are pointing in the same direction

4. Calculate the model

5. Select both nodes and export them to the RC Spread Footing module answering yes for the two column foundation question.

 

Which of these points do you find difficult? 

 

When reaching the underlined (answering yes for the two column foundation question.), the module will design single footing (not a combined footing between two nodes). Please try yourself and answer me.

 

 

Message 14 of 17

 

When reaching the underlined (answering yes for the two column foundation question.), the module will design single footing (not a combined footing between two nodes). Please try yourself and answer me.

 

It seems that we either have different understanding of what a combined footing is or the results you get is different than mine . 

 

The combined footing as I understand it is:

 

combined footing.PNG

 

 

combined footing Robot.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 15 of 17

Hi

 

After posting the rtd file, dividing bars, rotating bars, removing rigid links, it's the time for combined footing definition.

 

Dear

 

If I design single column footings, they interfere.

 

I suggest a solution. Can I model the (one) footing under the two columns as a panel (with elastic soil)?

 

What should be the dimensions of this (one) footing?

Message 16 of 17

What should be the dimensions of this (one) footing?

 

 

Message 17 of 17

Hi

 

If you fillowed the posts, then you could know that your attachement couldn't solve the situation.

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