semi submerssible

Anyone have good reference for calculating steel weight for Compact Semi Submersible ?

It really depends on the hull form, are we talking pontoons and columns, SEALION, or narco hauler?

talking about CSS Compact Semi-submersibles - Vard Marine https://vardmarine.com/vessels/css-designs/

Assuming this is for the first turn around the design spiral, I'd estimate based upon SWATH builds that structural steel weight is 175% of the weight of the shell plating for the hull alone (i.e. bare hull weight without decks and house = shell weight + 0.75*shell weight). That hull form is very structurally inefficient. For a preliminary design, the class society is generally going to dictate the shell plating thickness, so a preliminary estimate of the supporting structure is needed. A typical steel ship hull weight is ~ 135% of the shell weight. The deckhouse will follow more normal convention of ~ 120% of the house plating. Once you have a viable preliminary design, you can flesh out primary, secondary, and tertiary loads, which will set the hull structure (Bulkheads, frames, longs, etc ) for the next weight estimate. Turn the crank through the design spiral several times and the weight will fall out.
You DO NOT want to under-estimate the hull weight in the original concept. It is easy to add ballast, hard to add buoyancy.