topic Re: Composite section analysis in Robot Structural Analysis Forum

Composite section analysis

EY23 — Wed, 05 Sep 2018 12:17:49 GMT

Dear all,

I'm trying to simulate an encased concrete composite section. But the analysis took much time and part of the drawn section were neglected by robot.

Any Ideas?

Re: Composite section analysis

Artur.Kosakowski — Wed, 05 Sep 2018 12:24:36 GMT

Hi @EY23

Could you attach Robot file and screen captures which explain the situation?

Re: Composite section analysis

EY23 — Wed, 05 Sep 2018 12:30:45 GMT

@Artur.Kosakowski Thank you for your reply.

Kindly find attached files

Re: Composite section analysis

Artur.Kosakowski — Wed, 05 Sep 2018 13:27:55 GMT

Hi @EY23

You need to redefine the section shape:

If I managed to answer your question(s) press the Accept as Solution button please. This will help other users to find solution(s) much faster. Thank you.

Re: Composite section analysis

EY23 — Wed, 05 Sep 2018 13:37:58 GMT

My section has 2 types of concrete..
the internal beam 14 mpa and the external 30 mpa. in ur case the concrete
type is similar

Re: Composite section analysis

Artur.Kosakowski — Wed, 05 Sep 2018 14:15:09 GMT

Hi @EY23

So it was what was intended but not done exactly as such

Please change the material of the outer section as 30mpa concrete was not defined in the section you sent therefore I wasn't able to assign it. Mind that the rebars can be of slightly different diameters as well.

If I managed to answer your question(s) press the Accept as Solution button please. This will help other users to find solution(s) much faster. Thank you.

Re: Composite section analysis

EY23 — Wed, 05 Sep 2018 16:32:00 GMT

I tried it but it neglected the bottom rebars- when I cilec in the circles it shows that they are steel. but in the analysis they are neglected as if they are not moved at the top of the face

Re: Composite section analysis

EY23 — Thu, 06 Sep 2018 07:46:40 GMT

Dear @Artur.Kosakowski

When I transfer the section to the modulus the shear Modulus G any suggestions?

Re: Composite section analysis

Artur.Kosakowski — Thu, 06 Sep 2018 08:49:37 GMT

Hi @EY23

Make sure you defined G in the material properties of 14mpa concrete material in Job Preferences before you created the section in the Section Builder module and that the cuts are at the locations of rebars:

If I managed to answer your question(s) press the Accept as Solution button please. This will help other users to find solution(s) much faster. Thank you.

Re: Composite section analysis

EY23 — Thu, 06 Sep 2018 09:01:03 GMT

@Artur.Kosakowski thank you for your reply.

kindly find attached the pictures showing 3 cases.

My section is made of 3 materials:

-why the Ix and Wx are not calculated?

-G is defined for all types of concrete, why it isn't calculated in the section.

-for the same load Fz for the composite section is larger than the ordinary one the pictures shows

Re: Composite section analysis

Artur.Kosakowski — Thu, 06 Sep 2018 13:16:27 GMT

Hi @EY23

-why the Ix and Wx are not calculated?

These values are not calculated for the composite sections. You can enter them using the Section Browser in the User Section database based on the results obtained for the concrete section of the same shape.

-G is defined for all types of concrete, why it isn't calculated in the section.

As the final section properties are weighted based on E of the composite section components assigning the corresponding G value is not possible. On the other hand its influence would be only visible if you include shear in the deformation which you usually don't for ribbed slab.

-for the same load Fz for the composite section is larger than the ordinary one the pictures shows

As the composite beam is more rigid than the 'standard' one it 'attracts' more load from the slab. Compare the deflection of both beams.

If I managed to answer your question(s) press the Accept as Solution button please. This will help other users to find solution(s) much faster. Thank you.

Re: Composite section analysis

EY23 — Thu, 06 Sep 2018 13:28:23 GMT

@Artur.Kosakowski thank you for your reply.

I Have also one last question. Is there any way to reduce the stiffness of the composite beam in the model in order to get more realistic results regarding deflection? (0.35 Ig for beam)

Re: Composite section analysis

Artur.Kosakowski — Thu, 06 Sep 2018 14:22:46 GMT

Hi @EY23

The only way I can think of is to edit its Iy value in the section database.

If I managed to answer your question(s) press the Accept as Solution button please. This will help other users to find solution(s) much faster. Thank you.