I have a structure which is essentially a curved beam (not an arch or anything simple) which I have modeled in microstran/spacegass. It looks something like this:
The definition of stiffness as I know it is: k = F/d
ie the stiffness of a structure in a direction is proportional to the Force applied to the location divided by the deflection of the structure at that location due to that force.
However in the case of these structures, the stiffness will vary depending on the direction I apply the load.
I have applied a downward load of 1 N to the center of each of the 'arches' and they deflect accordingly. However, they obviously deflect differently (in magnitude) when I apply an upward load at the same location. Note: I am doing a non-linear analysis.
So which is the correct deflection that I need to use in my calculation of k = F/d?
I am using this stiffness for structural dynamics purposes, I am trying to find the natural frequency at that location. The structure will therefore vibrate in both the upward and downward direction.
My initial thought was to apply a load of 0.5N in both directions and add the deflections. Would this be correct?