Signboard Design

(a) I don't know your code, but wind pressure would seem to be fairly elementary, so yes, you should be able to determine the design wind load.

(b) An FEA study for this structure seems like overkill to me. You must state whether the 1000 mm is vertical or horizontal. It makes a big difference. Assuming the 1000 mm is the vertical dimension, you need to define the width of post. If the post width is 100 mm and the horizontal dimension of the sign is 500 and the post extends 800 above the bottom of the sign, the cantilever each side and on top of the post is only 200 mm.

If the post width is 100 and the horizontal dimension is 1000 mm, the cantilever is 450 mm. Either way, the calculation can easily be performed by hand.

(c) Once you have determined the above criteria, 3D models and orthographic drawings should be a piece of cake.

Although I am not familiar with it either, BS 6399-2:1997 was superseded by Eurocode 1. I will assume it is consistent with general physics.

For item (a) in post 0, let's say, e.g., you want to design your signboard for a wind gust speed of v = 50 m/s. And let's say the air density is rho = 1.33 kg/m^3 (cold, wet day, with high barometric pressure). The drag coefficient for a flat, rectangular plate of vertical height h = 1000 mm, and width b = 500 mm, oriented at an air impingement angle of zero (normal to wind), is Cd = 1.18. Therefore, the wind pressure on your signboard would become pw = 0.5*Cd*rho*v^2 = 0.5(1.18)(1.33 kg/m^3)(50 m/s)^2 = 1960 Pa.

It would be interesting to see how the above pw value compares to Eurocode 1. Now you can analyze the plate and pole. I am not sure what yield factor of safety, FSy, Eurocode 1 would require for this; but it is perhaps something like FSy = 1.50 (?).