There are two reasons why the value of Sx develops on the plate elements –
*Due to Poisson’s effect (which is an insignificant portion) on the plates resembling both beams and columns
*You will see quite significant SX stresses develop on the plate elements resembling beams. This SX values resembles the bending stress would should roughly match M/Z values at the extreme fibres of the beam. If you look into the SX contour the bending stress distribution can be seen clearly.
For the beams, you will be designing the reinforcements to take bending – which will take care of the significant portion of the SX stress.
The stress due to Poisson’s effect in both the beams and columns need not be accounted for. The reinforcements provided should be able to cater for it. However, please consider this as a suggestion only and take the decisions at your discretion.
