buckling of curve plate

huangyhg

buckling of curve plate
hi all,
i am currently working on a helical stair case made up of a spiral steel plate as the interior stringer.  this plate is approximately 1.25" thick x 52" deep and it spans story to story making a 360 degree turn.  a finite element model has been built and stress on the plate seems to be okay.  however, does anyone has any suggestion on how to go about investigating the buckling issue of the curve plate?  does anyone know of any formula or reference to determine the buckling load of a curve plate?
thanks for your help
kai ki mow
check out our whitepaper library.
is the plate restrained at supports? if not restrained than buckling may pose a problem. that in turn will reduce its capacity.  
what software r u using?
inform us of the connection details too.
normally the flight lateral torsional buckling is controlled by the treads spanning between the 2 plates. these forces act inwards but at the same time allow for a spring action of the entire stairs especially when u have a 360 degree turn!.