in order to check how far is the part from failure in case of biaxial or triaxial stress ,various criterions were developed.these are called failure theories.
in my field (lifting appliances) codes define the equivalent stress as:sigma=sqrt(sigmax^2+sigmay^2-sigmax*sigmay+3*tau^2).this should be...
if you really do not know how to begin, i would advice you to hire a design or design and fabrication according to your specifications.
such appliance has to be designed and build according to some recognized code which will define the safety factors and other important parameters that will...
the bent you noticed,seems to me of no significant problem.
if you want to calculate, here is my suggestion:
the bent puts eccentric load which mean bending monent of [force]x[eccentricity] on the rectangular strut. calculate both the strut and the fillet weld to the plates for this moment.
zvi