FEM Model problems bridge

[DennisVDijk]

Hello there,

I try to model a bridge in ROBOT. I did some bridges before but never totaly in FEM. I have some difficulty to make my model right.

[1] I want to cut off a part of an panel whereby the cutting line is the cilindrical tube, see pdf. tips to cut these panels are welcome!

[2] is it normal that the material properties of the panels are not been shown?

Attached my model so far.

[Rafacascudo]

Model has no panels ,no bars . Only a few nodes and some lines.

Also ,no pdf.

[DennisVDijk · Accepted solution]

Hello,

Thanks Rafacascudo for looking to my model. I think i put the wrong model to my post.

In the meantime i found the solution to make my model right. See pictures:

Hereby the section that i want to cut. i did this with command object commbinations:

 

I also attached my model so someone else can learn from it.

[Rafacascudo]

Congrats ! Very nice model!!

Do you really need the tubular sections of the protection railway to be modelled as panels( cylinders)??

Talking about that ,there are 4  assigned with different thickness compared to the rest of them

[StefanoPasquini6790]

Hi Dennis

Very nice model. However, my personal suggestion is to "semplify" as much as you can your model for many meanings:

First of all, the handrails have not influence in the structural behaviour of the whole model. I could substitute it with a linear load. Many objects you have in the model and more objects you have to manage.

Second: your time calculation will increase with the number of elements, if you consider that probably you have to use moving loads....your time consuming will be multiplicated for much times...

Third: the results accuracy is much better with beam elements instead of shell elements. To full understand this, try to make the same model of the bridge with bar elements, so that you can make a comparison between the models.

My personal experience in structural analysis, 15 years, have learned me that the most important rule, in all the structural problems, is that you have to do for first a simple model, that give you the opportunity to fully understand the global behaviour of all the elements. Only after this you can go further with more complicated models.

We are curious to see the tensional and deflection difference between the two models, then please make a bars one and post the comparison.

Good luck and see you soon

[DennisVDijk · Accepted solution]

Hello Stefano,

Thanks the you took some time to look at my model.

With this bridge project I wanted to explore the posibilities within ROBOT to use FEM and compare this with another programme.

For the behavior of the bridge i also made a simple 2D beam model to check the results.

You are right with the FEM results about the accuracy. In some points there are large peak stresses. This probably is the result of elements that are not connected well. 

When I had was anough time I would make a model with bars in ROBOT. Maybe I will soon, when I do this I shall post the results.

Cheers,