RC beam horizontally supported by the steel beam?

[greznik91]

Hello,
I'm dealing with the RC structure(moment frames in both dfirections) with masonry walls/infills between RC walls/columns.
Only the small part of the building plan has RC slab on the top – the rest of the structure is 'opened' - doesn't have RC slab on top so the timber roof is the only diaphragm (plywood sheating + diagonal steel straps on rafters).

The middle RC beam with cross section of 400x800 mm is supporting the roof – the span is 10 m.

Question: I image that in case of the earthquake the middle beam will 'swing' left and right (perpendecular to the beam axis/line) since it is long and heavily loaded. Is there any point/reason to add a steel beam (red line in the attached image) that will prevent this action? But at the same time it will cause shear forces on the beam. What is your suggestion/opinion on this.

 

[greznik91]

Anyone?

 

[KootK]

I don't feel that you need the steel beam. I feel that it would not be a very big deal to just design the RC beam to deal with its own, inertial seismic load.

It's conceivable that the beam might see a bit of axial compression during seismic shaking. As such, perhaps it deserves a bit of stockiness just for that reason.