Your style to put roof beams or rafters

[mes7a]

Please refer to the above image. A shallow two sides (garble) will be put at the 9 RC column layout. My colleague initially make the suggestion of putting the beams the following way. He plans to put empty square bars (see picture) with size 250mm x150mm x 8mm thick) at the perimeter (see red picture of beams connecting the columns) by welding it to the sides of the column (via metal plates anchor bolted to the sides of the column). The perimeter beams will carry 1 meter high parapet RC wall. If you will do it. Will you put the perimeter beam at the sides of the columns or on top? I suggest better on top.. but we need to weld the rafters on top. Can you give references of the typical connections and what is the strength if different connections use. I mostly design Reinforced Concrete structure but not yet a lightweight metal roof. And I thought if the perimeter beams would just be welded to the sides of the columns.. and there is seismic activity.. the beam connections at side may shred and the parapet wall would fall down.. whereas if the perimeter beams are on top of the columns. It's more stable. But how to do the connections (typically in different countries)? The columns are size 0.5x0.5 meter with 4 corner 16mm bolts above and the distance between the columns are all 6 meters. Thank you.