Composite Beam Design?
Composite Beam Design?
(OP)
Hello everyone.
I am currently analyzing a composite beam consisting in two cold formed steel channels bolted together and filled with 3000PSI concrete (as shown in the attached picture).
I did a model with ETABS of the whole structure using this beams. ETABS allows you to model and design "Tubes Filled with concrete" and I can obtain the stress/ratio capacity and
all internal forces of the member.
The thing is, this is all assuming that both channels behave as one steel tube. For this to happen, I need to provide enough anchors along the span of the beam to resist all internal forces.
How can I analize this? Is the maximum torsion and moments (Mu2, Mu3) in the beam supported by all bolts together?
I am currently analyzing a composite beam consisting in two cold formed steel channels bolted together and filled with 3000PSI concrete (as shown in the attached picture).
I did a model with ETABS of the whole structure using this beams. ETABS allows you to model and design "Tubes Filled with concrete" and I can obtain the stress/ratio capacity and
all internal forces of the member.
The thing is, this is all assuming that both channels behave as one steel tube. For this to happen, I need to provide enough anchors along the span of the beam to resist all internal forces.
How can I analize this? Is the maximum torsion and moments (Mu2, Mu3) in the beam supported by all bolts together?






RE: Composite Beam Design?
RE: Composite Beam Design?
RE: Composite Beam Design?
I'm also a little wary of calling this fully "composite" when there is nothing really holding this concrete together internally (since it is 4" x 8").
You also have to watch out if this thing is picking up axial loads. That can change your hold down needs considerably.
RE: Composite Beam Design?
AISC 360-10 Section F13.4 describes build up sections in flexure:
Where two or more beams or channels are used side by side to form a flexural member, they shall be connected together in compliance with Section E6.2.
Section E.6 describes built up sections in compression. Get you max compressive force from your moment envelope (Mu/d) and determine a, the distance between connectors in accordance with E6.2. This will only ensure the two channels work together as one built up section, not as a steel/concrete composite section. Other requirements are necessary to develop a fully composite section.