Assigning Composite Section to Bars

[Anonymous]

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

[Artur.Kosakowski]

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.

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[Anonymous]

Hi Thanks so much!

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

[Artur.Kosakowski]

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

[Anonymous]

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. 

[Anonymous]

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

[Artur.Kosakowski]

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

[Anonymous]

Sent from my iPhone

[Artur.Kosakowski]

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

[Anonymous]

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

[email protected]

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

[Artur.Kosakowski]

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

[Anonymous]

Please find the section user database attached as well

[Pawel.Pulak · Accepted solution]

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,

[Anonymous]

Thanks so much Arthur. It was very helpful.