Light gauge metal frames
Light gauge metal frames
(OP)
I am trying to analyze an existing carport that uses CEE sections (8" x 2-1/4", 14 gauge) as columns and a beam of a frame. The height is about 8' and the frame width is 10'. The columns are embedded in concrete. The beam is connected to the side of the columns with screws (no moment is transferred). This is in California and I believe that free-standing carports are supposed to be designed for seismic forces as well. Because of the complex geometry of the sections, I'm having a hard time with the analysis. Do I use the same beam-column interaction formulas from ASD? Does anyone have any section properties that they can send me? I'm going to assume a rigid connection at the beam to column node. How would I achieve this connection in the field?






RE: Light gauge metal frames
Regards
RE: Light gauge metal frames
I can't use x-bracing because it would run straight through the parking areas. By inverted pendulum system, are you saying that I can just leave the connection as pinned at the top of the column and assume that it acts like a cantilever instead of acting as a frame?
RE: Light gauge metal frames
At any rate, you use the AISI spec to get your effective properties. This is because light-gauge members are very prone to local instability and you have to find the "effective" properties at the load for which you are designing. In addition you still have to consider lateral-torsional buckling and so on. Because these are thin-walled members you will also have different equations to find the nominal strength than those you will find in the AISC spec.
You will not find much literature on moment connections with metal studs, especially with self-drilling screws only. Also, do not assume to do an elastic analysis on the screw connection to find the moment the screw connection can handle. You have no way that I know of to check the stud web in addition to the screws. I would definitely assume the beam to column is pinned from what you describe. Try checking the columns as cantilevers from the base instead of checking the them as part of a moment-resisting frame. When I need to make a frame I use instead braced frames or knee braces. Those can help considerably. You just have to watch your connections carefully then.