Composite properties

[Anonymous]

Hi

I have a composite slab modelled with steel beams. I have offset the beams so the top flanges meet the underside of the composite slab.

Is there a way of exracting the resultant I values when the members are arranged in this way?

Thanks for your time

Oscar

[HoshangMustafa]

Hi

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[StefanoPasquini6790]

Hi Oscar,

Composite beam is a very hard item, and it's really difficult that one structural analysis software can give you the "perfect" solution.

Using the eurocode 4, you have to define the part of effective slab that collaborate to the composite beam strenght.
This must be done for the long terms loads and for the short terms ones.
You have to evaluate also the hyperstatic action of the shrinkage, that cause a moment in the beam (for the eccentricity of the slab with the beam)...
There are many other things that you have to evaluate for the right definition of composite beams.

The model that you have done is only an indication of the right analysis, I suggest you to create your own spreadsheet and check the structure with it, using octopus or API, you can do a very good job.

Let me know your choise.

[Anonymous]

OK great sounds good. I will have a look at Octopus now.

I am less concerned with the deisgn at this point in time, I am more intersted in whether the behaviour of the system is realistic i.e. will deflections and sway reflect the stifness of the composite system? I have modelled the concrete with a large reduction in its modulus to simulate craked concrete (so areas of tension are taken by the steel only).

Will this produce realistic stiffnesses of the composite system and in turn provide realistic deflection outputs? 

Thanks for your time

Oscar 

[StefanoPasquini6790]

Hi Oscar,

My suggestion is to do some tests. Try to model a simple composite beam with deck that have the elastic modulous ratio = 6 and model the same beam with the modulos ratio =17. Compare the results that you get with the theretical ones, so you can validate your model.

Greetings