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Contributor
sj352
Posts: 11
Registered: ‎01-03-2013

Timber frame

505 Views, 12 Replies
01-05-2013 03:19 PM

Hello, 

 

I've been looking over my work for ages trying to find out what  I have done wrong, but I really dont know. Could you plese look at the attachment, it is a portion of my project, and briefly tell me how could I improve it. Im particularly interested in finding the mid-span deflection for beam number 18. I found it to be 4 mm but I would expect it to be much higher number.

 

The floor is timber-concrete composite and I chose cladding on the top level to account for the flat roof. I have performed offset on all beams, so that the concrete slab is sitting on the beams.

 

Could you please tell me why is the deformation so small?

 

Thanks

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Product Support
Artur.Kosakowski
Posts: 4,736
Registered: ‎12-17-2010

Re: Timber frame

01-07-2013 12:17 AM in reply to: sj352

What is the way you calculate the deflection? Do you include the slab stiffness and take into account the fact that the vertical offset increases the stiffness of the beam? Try to change the panel calculation model to the curtain wall and compare the results.



Artur Kosakowski
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Contributor
sj352
Posts: 11
Registered: ‎01-03-2013

Re: Timber frame

01-07-2013 11:37 AM in reply to: Artur.Kosakowski

It's a school project, I need to find the mid-span deflection of the "front" beam - number 18 using Robot analysis. And then I have to compare it to my "hand calculations". And see the accuracy. But it's getting more and more tricky because I don't have proper understanding of what, why and how to do. 

 

I would like to put a RC slab on the first floor. So could you please advice on how to design the reinforcement using the robot only, without estimating my own values if possible.

 

Once I do that, I want to find the deflection of the previously mentioned beam, taking into account the self weight of the structure and live load applied to both top cladding and RC slab. 

 

I normally just right click on the beam, click on object properties and displacements in UZ direction.

 

But it only gives me the displacement of 0.3-0.5 cm, which seams to be much less than I would expect. 

 

So Im getting desperate and have no idea what to do.

 

Could you please help me?

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Contributor
sj352
Posts: 11
Registered: ‎01-03-2013

Re: Timber frame

01-07-2013 11:39 AM in reply to: sj352

No I dont include slab stiffness or offset. So will I be able to compare robot results with simple hand calculations?

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Product Support
Artur.Kosakowski
Posts: 4,736
Registered: ‎12-17-2010

Re: Timber frame

01-07-2013 11:57 PM in reply to: sj352

If you create similar model in Robot to the one you use for hand calculations the results should also be similar :smileyhappy:

 

Perhaps you should just apply the same load you used for hand calculations to the beam directly and do not model the slab. Looking at your description I assume this is what you assumed for your hand calculations.

 

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
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Contributor
sj352
Posts: 11
Registered: ‎01-03-2013

Re: Timber frame

01-08-2013 08:06 PM in reply to: sj352

I promise this is my last question.

 

When Im analysing my structure, I want to find out the map of deflection of my slab. But it seams that it sort of does not take beams into an account (see pics). I would expect the max deflections to be within each of the "smaller floors". 

 

Also if I simply draw counter-panel slab on the beams. What is the relationship between a slab and beams? I mean what kind of support.

 

 

Thanks

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Product Support
Artur.Kosakowski
Posts: 4,736
Registered: ‎12-17-2010

Re: Timber frame

01-09-2013 02:27 AM in reply to: sj352

This depends on the model you have created/generated. Could you send it?



Artur Kosakowski
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Contributor
sj352
Posts: 11
Registered: ‎01-03-2013

Re: Timber frame

01-09-2013 03:08 PM in reply to: Artur.Kosakowski

Here it is. Why wouldnt my beams bend under the combined load?

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Product Support
Artur.Kosakowski
Posts: 4,736
Registered: ‎12-17-2010

Re: Timber frame

01-10-2013 01:21 AM in reply to: sj352
When Im analysing my structure, I want to find out the map of deflection of my slab. But it seams that it sort of does not take beams into an account (see pics). I would expect the max deflections to be within each of the "smaller floors". 

 

1. Case 1 has got no defined loads

2. Case 2 - loads applied directly to beams therefore such effect as you described cannot happen

3. Case 3 - you need to define smaller mesh size (e.g. 1m) and reduce the thickness of the slab. The 20 cm on span of 2 m means that slab carries beams rather than is supported by them. Try e.g. 5 cm instead.

 

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
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Contributor
sj352
Posts: 11
Registered: ‎01-03-2013

Re: Timber frame

01-10-2013 03:57 AM in reply to: Artur.Kosakowski

3. Case 3 - you need to define smaller mesh size (e.g. 1m) and reduce the thickness of the slab. The 20 cm on span of 2 m means that slab carries beams rather than is supported by them. Try e.g. 5 cm instead

 

 


Why is that happening?

 

This was just a portion of the model and the whole model has smaller dimensions of the beams. How can I make sure that the beams carry the slab and not the other way around?

 

Thanks

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