Beams

[engVassilev]

I want to use steel design options according to EC. In the Steel design manual book I read, that there is a classification of the frame elements, according to their position in the model space. If they're parallel to z axis, they are columns. These which are parallel to x-y plane are beams and the rest are braces.
My model has a sloping roof and I want to design the roof beam. But does SAP take it in like a beam, or like a brace?

 

[engVassilev]

And also, if SAP considers it like a brace, is there any way to change the type of the element to a brace?

 

[johnbridge231]

As SAP proceeds to a biaxial design for every structural element, even if it is a column, beam or brace, I would not concern much.
On the other hand, SAP uses by default a buckling length factor equal to 1.0 for braces and beams. So, if buckling is critical, you may then want to override that value for the design preferences of that sloped element.

Analysis and Design of arbitrary cross sections
Reinforcement design to all major codes
Moment Curvature analysis

http://www.engissol.com/cross-section-analysis-design.html

 

[engVassilev]

This time was my first time, when I used the design precedure of SAP2000 for steel structures. I've got purlins, which I modeled in my 3D model, and I have a joint at the intersection point of purlin and the sloped roof beam. So at the end of modelling my roof beam consists from n frame elements. According to the EC3 when I have a purlin, I can accept, that the top flagne of my roof beam is stabilized against lateral-torsional buckling in each joint, where I have a purlin, connected to the beam. So the effective length in this case is equal to the distance between the purlins ( which is the length of each separated frame element of the beam). In this case K LTB in SAP2000 should be taken equal to 1, as the program do it automatically.
Is my supposition true?