topic Re: Hybrid Beam Design in Robot Structural Analysis Forum

Hybrid Beam Design

Anonymous — Fri, 10 Aug 2012 16:27:53 GMT

Hi.

I'm looking for the best way to analyse/design a hybrid beam with flanges in S275 steel and web in S235 steel.

I start by define a parametric section all in S275, and then compare result with same section all in S235.

In order to optimize design, I create an hybrid section, as mentioned before, on Robot Section Definition, but the ULS racio got worse...that seem strange.

So, I noticed the following points:

The section from section definition don't have torsional properties (Ix=0). Why? I select it to calculate, but the program don't assign it:
Yield and limite stresses for the hybrid section are weird. Where the 120MPa came from?I try to homogenize on S235 and on S275, with same results for both.

Any ideas what is happening and what's should be the best approach to this problem?

Thanks

Re: Hybrid Beam Design

Artur.Kosakowski — Mon, 13 Aug 2012 12:19:52 GMT

Hybrid beams are not supported in the Steel Design module.

Re: Hybrid Beam Design

Anonymous — Mon, 13 Aug 2012 12:55:27 GMT

Even so, couldn't I use the Section Definition Module to assess elastic and plastic characteristics of the section?

Although the hybrid design is not available in Steel Design Module, I need its correct properties to proceed by hand verifications.

Re: Hybrid Beam Design

Artur.Kosakowski — Mon, 13 Aug 2012 13:33:51 GMT

I'm not sure if I understand correctly which characteristic you want to calculate yet as Young modulus for different steel grades is the same this should not be a factor. On the other hand you can calculate weighted characteristic for the material you selected as the base one (e.g. timber flanges C16 and S235 steel web).

Re: Hybrid Beam Design

Anonymous — Mon, 13 Aug 2012 22:35:45 GMT

Ok. I was even talking about that characteristics.
As your example resumes, it's possible to get them from the Section Definition Module, at least some of them.

My doubts came because, as you could see in previous pictures, the "hybrid beam" in a steel base material has identical characteristics to the one in just one type of steel (Wpl,y=10301.23). This can't be right. Which cause me to question the way this module work.

When I import some section defined in the Section Definition Module, only the elastic characteristics are correct?!

Why the element don't have torsional resistance (Ix=0)?!

Please, if possible, can you make a simple example/tutorial in how to use the Section Definition Module, in order to get, besides section analysis results, all the necessary properties for assign to bars in a global analysis.

Thanks Artur.

Re: Hybrid Beam Design

Artur.Kosakowski — Tue, 14 Aug 2012 08:30:08 GMT

Make sure you marked the check boxes and pressed Calculations button below them before saving the section to the user database.

The plastic characteristic are not used for static calculations of the model. In case a section is to be code checked they are calculated inside the steel design module itself.

Re: Hybrid Beam Design

Anonymous — Tue, 14 Aug 2012 19:30:56 GMT

I have checked each box.

It just don't calculate torsional constant for hybrid sections. I tried it with a regular one and the program calculate torsional constant just fine (Ix).

Any idea what's happening?

Thanks

Re: Hybrid Beam Design

Artur.Kosakowski — Thu, 16 Aug 2012 07:03:19 GMT

For the same E values for flanges and a web you can calculate Ix as for the one material section. In general the section builder module is not capable of calculating Ix for sections with different materials.

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