Rigid link vs Diaphragm

[Refaat]

Dear Colleagues

In the attached files, I modelled RC slab with diaphragm once and with rigid link once again. I expected to get a similar results for both applications. But unfortunately I couldn’t

Please, take a look to the attached captures and dummy model files and give me illustrations for these discrepancy:

• The vertical displacement at column locations in (Slab- Rigid body diaphragm model) aren’t symmetrical as we have in (Slab – Rigid body link model) … capture 000.

• The distribution of loads generated automatically doesn’t make sense for both cases …case 001.

• When I applied (flexible diaphragm & flexible link) (capture 002) . I have got more reasonable results for (flexible diaphragm model). But still don’t equal to the results of (flexible link).

• Since most of RC structures treat floor slabs as (Rigid diaphragms) (No horaztional deformations in slabs) (Ux , Uy and Rz all blocked) . Does mean that we have to use (Partial stiffening in XY) as (Rigid diaphragms) when we want to treat the slabs as rigid diaphragms. Please, correct me if I am wrong concerning this concept.

https://www.dropbox.com/s/k2rn93d3z8bwiva/Rigid%20link%20vs%20Diaphragm.zip?dl=0

With Regards

Refaat

[Artur.Kosakowski]

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[Refaat]

Dear Artur

Thank you, I should pay attention to this option.

But may I know your opinion about the following inquiry:

• Since most of RC structures treat floor slabs as (Rigid diaphragms) (No horaztional deformations in slabs) (Ux , Uy and Rz all blocked) . Does mean that we have to use (Partial stiffening in XY) as (Rigid diaphragms) when we want to treat the slabs as rigid diaphragms. Please, correct me if I am wrong concerning this concept.

Thanks a lot....as always.

Refaat

[Artur.Kosakowski · Accepted solution]

This is correct. If you don't use shell panel calculation model it should be

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[Refaat]

Dear Artur

Please, take a look to the attached capture. It seems to me that the definition of constraints codes for partial stiffening diaphragms needs to be corrected in display.

Thanks

Refaat

[Artur.Kosakowski · Accepted solution]

What you have displayed are the definitions of supports created in the automatically generated calculation nodes which are the master nodes of the rigid links and they are correct. What you refer to are d.o.fs of the rigid links instead.

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[Refaat]

Dear Artur

Thank you for this clarification

Refaat

[ByrnePM]

Hi Artur/Reefat,

Artur: Why is it correct to use partial stiffening diaphragm instead of full stiffening diaphragm when modelling the action of diaphragm RC slab?

Thanks

[Artur.Kosakowski]

Full stiffening (rigid body) would also impose restrains for vertical displacements and all rotations.

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[Anonymous]

Hi Artur,

Can I seek clarification - why does the flexible diaphragm type model show restraint in the master node in UZ, RX, RY? 

Thanks

Tony

[Artur.Kosakowski]

Hi Tony,

As in this type of the diaphragm rigid links impose constrains only on the horizontal (UX and UY) directions (imagine bars connecting a master node with slave nodes with UZ, RX, RY, RZ releases at the slave nodes) you have to somehow prevent the master node from 'going' down or spin around.  

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