Is there a guide as to how to model a built up column in Ram Elements with various section properties across its height?
I'm looking to design a column that has changing section properties across its height. It would not be linearly tapered but more like a hot rolled section fastened to another hot rolled section for only a certain height. ASIC Design Guide 25 provides guidance as to how to analyse non prismatic sections in compression. When I try to duplicate results in Ram Elements they do not match since the K and Lu in Ram Elements does not account for multiple section properties for buckling, or at least I'm not aware as to how to properly model such a column and capture its buckling behavior properly.
I see there's a section for built-up members under compression but even when altering the fastener spacing I still get the same capacity.
Please advice if possible. Thank you.
If you have two members that are fastened together you probably want to use a custom section. Here is some basic information: https://communities.bentley.com/products/ram-staad/w/structural_analysis_and_design__wiki/3569/creating-custom-sections-materials-etc-in-ram-elements-tn
There is a bit more int he program help - Chapter 16.
You can use a General (Gen) type section if that is simpler (i.e. where you know the area and inertia already), but steel design is not performed on Gen sections.
If you are using a design-able section and the section changes away from any brace point, then you will need to override the program K and L factors. The fastener spacing control is for double angles.
Distance between connectors in built-up members. It is used to calculate the modified slenderness of the built-up member following Section E6 specially 2L sections.
If a (Connectors) = 0 the application assume a connector at the beginning of the member and another one at the end only. Thus, the distance is the full length of the member. That is on the conservative side anyway.