topic Re: Assigning Composite Section to Bars in Robot Structural Analysis Forum

Assigning Composite Section to Bars

Anonymous — Thu, 21 Apr 2016 06:36:56 GMT

Hi ,

I was trying to model a composite section in robot. Just for testing I built a simply supported 10m beam to check if the reactions are correct under self weight.

This is the composite section i tried to model,

Weight of this beam is about = 158.3 kN/m - which should give me a reaction of 791.5 kN (for a 10m long simply supported beam)

Section Area: Depth = 4 m, Width = 1.4 m, A_total= 5.6 m2
Steel Plates (3 Nos): Depth = 1.3 m, Width = 0.1 m, A_steel = 0.39 m2

Area (m2) Density (kN/m3) Weight (kN/m)

Asteel 0.39 78.5 30.6

Aconcrete 5.21 24.5 127.6

I built this section is robot using,

Tools---->section builder (where i clearly specified the concrete and steel bits of the section).

I saved the section to database, and assigned to the bar

But in robot, i have to give the bar section a material property. So i assigned concrete to it and it gives a really high reaction (about 900kN).

How can i assign a single material property to a bar when it is composite seciton! every time i change the material (so the material i assigned during section definition is invalid). What is the use of defining a composite section then?

Can anyone help? and explain how to use section buider to define composite section and assign it to a bar? and get the correct behaviour?

Thanks and regards,

Vikas Venkatesha

Re: Assigning Composite Section to Bars

Artur.Kosakowski — Thu, 21 Apr 2016 06:54:38 GMT

Do not change the default material after defining a bar in a model as the weighted properties of the section are calculated for the material you selected while defining the section in the Section Builder module.

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.

Re: Assigning Composite Section to Bars

Anonymous — Thu, 21 Apr 2016 07:54:09 GMT

Hi Thanks so much!

That is exactly what i need, but somehow my default material comes as ALUM,

Re: Assigning Composite Section to Bars

Artur.Kosakowski — Thu, 21 Apr 2016 08:05:05 GMT

Could you check if the information about the composite material is stored in the properties of this section?

Re: Assigning Composite Section to Bars

Anonymous — Thu, 21 Apr 2016 08:27:09 GMT

Hi Artur,

I checked the data base. It looks like you have eurocode in your preferences. I have british standards. Anyway i changed it eurocode and tried again now the default material comes as C60. I cheked the section database, i think its alright. Here is a screenshot.

Re: Assigning Composite Section to Bars

Anonymous — Thu, 21 Apr 2016 09:47:44 GMT

Finally i got the material right, but still wrong reactions. Its really confusing. Please help. If you want i can email u the model.

Re: Assigning Composite Section to Bars

Artur.Kosakowski — Thu, 21 Apr 2016 09:51:33 GMT

Send me both the model and your user section database. Thank you.

Re: Assigning Composite Section to Bars

Anonymous — Thu, 21 Apr 2016 10:37:26 GMT

Sent from my iPhone

Re: Assigning Composite Section to Bars

Artur.Kosakowski — Thu, 21 Apr 2016 11:15:06 GMT

What about sending from a computer as no files were attached ?

Re: Assigning Composite Section to Bars

Anonymous — Fri, 22 Apr 2016 01:29:32 GMT

Hi Artur,

This link has the model. I have attached it with the post or you can also find it in the following links.

https://www.dropbox.com/home/Robot%20Composite%20Section#

Kind Regards,

Vikas Venkatesha

Assistant Structural Engineer

D +852 3925 9739

vikas.venkatesha@aecom.com

Benaim
7th Floor Prosperity Millennia Plaza, 663 King’s Road, North Point, Hong Kong

T +852 2527 0233 F +852 2527 6364

An AECOM Company

Re: Assigning Composite Section to Bars

Artur.Kosakowski — Fri, 22 Apr 2016 08:29:21 GMT

Could you send your user section database file as well please? Thank you

Re: Assigning Composite Section to Bars

Anonymous — Fri, 22 Apr 2016 09:11:38 GMT

Please find the section user database attached as well

Re: Assigning Composite Section to Bars

Pawel.Pulak — Fri, 22 Apr 2016 11:21:39 GMT

Hi Vikas,

thank you for sending the file containing your user section database.

Looking into it and comparing with your model I have noticed that the composite section label used in your model was not up-to-date with the properties in the database. Probably in the meantime you have modified this section.

It was necessary to:

1/ temporarily change the section in the model to different one

2/ delete the outdated composite section label

3/ define new composite section label basing on your user section database

4/ assign new label to bar in the model

5/ run analysis

I have shown it in this viddeo:

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Regards,

Re: Assigning Composite Section to Bars

Anonymous — Mon, 25 Apr 2016 01:44:43 GMT

Thanks so much Arthur. It was very helpful.