bracing of columns by wall girts

huangyhg

bracing of columns by wall girts
how effective are wall girts as bracing for a building column?   the "old" method of using a rolled channel as a girt seems to be more effective than a light gauge girt.  also, i would think that the method of connection would make some differece too.  for example, in some metal buildings the wall girts frame into the column web with clips, while in other situations the girts are outset and run by the face of the column - the girts are "continous".
is there any research on this?  i've always considered the column braced if girts were attached to it.
it would require a frame analysis to determine the loads sustained by the girt   
this is a torsional buckling problem.  see section 12.8 of "guide to stability design criteria for metal structures" by galambos.  if you don't have access to this book, you can email aisc's steel solutions center and ask them to fax you pages 3-4 and 3-7 of the yura/helwig 2002 stability seminar handout.
     i would not consider, when the girts are connected to the outer flange, as bracing the column against torsional buckling. i have seen a lot of metal buildings with small angles connecting from the girts into the column inside flange (frame braces). i guess this justifies as bracing against weak axis column buckling and flange ltb during bending, but it looks a little rinky dink to me.
   i would also be aware of the girts being cut by adjacent openings if they are being used to brace the column in any way.