Circular Formwork Skin Plate and Stiffener Design

[mrburberry]

Hey guys! I'm new to this forum.

I'm a fresh design engineer.

Currently this is my first month employed in a company.

Today was asked to design a 2m diameter, 5m height, 4.5mm thk. circular column metal formwork. Concrete density is 24kN/m3.
The lateral concrete pressure that i got is 64.65kN/m2 (based on BS)

However, i'm stuck in designing the spacing of horizontal and vertical stiffeners for the formwork skin plate.
should i treat the load which acts on the skin plate as a "2-way span"? if yes, what spacing should i use in my design.
i tried 0.5m spacing c/c for vertical stiffener and 0.6m c/c for horizontal stiffener on the skin plate. both pass in bending moment but fail at deflection.

the skin plate is 4.5mm thk. i calculate its second moment of inertia by using the formula bh3/12 which is 1000*4.5^3/12 and section modulus bh^2/6(1000*4.5^2/6). am i doing correctly? oh ya, we are using factor of safety =2 .

any kind soul could guide me?


ps: attached drawing for reference. (not the exact dimension, just an example)
pps: im a newbie design engineer. but i'm eager to learn. appreciate ur guidance!!

 

[prex]

Your drawing is not fully clear, a plan view would be useful.
However I understand this is a cylinder in two halves.
Your first worry should be the calculation of the flanges joining the two halves, there you have bending in the flange plate and tension in the bolts.
The skin, as it is circular, will sustain the pressure by its own with an acceptable stress, that can be easily calculated by formula (PD/2t). The purpose of the stiffeners is only to keep it circular during installation and concrete pouring. I don't know how you could calculate these, guess this is a matter of similarity with other successful designs.

prex
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[mrburberry]

hi prex!!
thanks for the reply!!

ya i had calculated the flange plate and tension in bolts. no problem for me.
thanks for your info on the stiffener.