The proposed "box truss" is sometimes called a Vierendeel truss and has been used occasionally in modern architecture. The omission of diagonal members means that the joints must be rigid (not pinned), complicating the structural calculations because the structure is then statically overdetermined. It's a promising design I think, compared to the clunky garden bridge proposed for London.
> How can a millennial ’trep with no lofty urban-design credentials even consider proposing such a bold idea?
What is a "'trep"?
Entrepreneur? I've never seen this used before either.