I’m modeling a composite bridge to run modal analyses and understand the natural frequencies of the bridge and I need some advice.
I’m using a beam model with a composite thin walled section and I’m wondering whether the effective width of the concrete is calculated automatically by aqua. From a few tests and the manual I’d understand it does, but how?
Also, in one of the tutorials it is suggested to use a shear connection with a width of 100mm between the top flange and the concrete, what is the range that can be used and why 100mm is suggested?
A big thank you to everyone that can help with this doubts
The effective width of a T-Beam or a composite beam is not calculated automatically. The width of the cross-section is processed as the effective width. Therefore please calculate the effective width according to your design code by hand and set the width of the concrete plate as wide as the effective width.
Oh ok, I misread the manual and the small variation in eigenvalues for my bridge, thank you so much for the explanation. So it is the same for Class 4 sections, correct?
I’d have another question about the shear connection. I read that “- Shear bonds in composite sections (T < 0)” on manual AQUA > chapter 3.40 WELD - Shear Connection. But I’m using Sofiplus, and from the tutorial I saw the use of 100mm. So is that value somehow related or do I just need to vary it until I get “good” values?
www.sofistik.com > Infocenter - Overview > Documentation - Tutorials > Design of steel structures > Cross-section class 4 concept
Now to your second question.
If you increase the absolute value of T, you increase the stiffness of the shear connection. This means that a large |T| represents a nearly rigid connection. I can’t tell you which value is optimal for your project, because it depends on your system.
The sign of the effective thickness T controls, if the shear forces is calculated in dowels or welds:
T < 0: calculation of shear bonds in dowels
→ Graphic > Design > External Beam Sections > Stress of material > Shear in dowels/welds
T > 0: calculation of shear in welds
→ Graphic > Design > External Beam Sections > Stress of material > in welds
