I've got to draw up a waler system for a sheet-pile vault. The client's typical practice has been to use HSS members for the walers (including struts, bracing, etc.)
The outside dimensions would be about 30 ft x 35 ft. I would rather make the "knee joints" at the four corners as mitered welded connections for strength, but that wouldn't lend itself to welding in place. OTOH, I COULD have the whole thing shop-fabbed and shipped out fully (or partly?) assembled.
I just don't have a feel for ALL the pros and cons here, or if it is even doable with a frame that big.