designing a RC frame that is connected to a buidling just by timber roof

[mats12]

Im wondering how would you guys design a RC frame (colums are 250 mm in diameter, beam is 400/300 mm) that is around the building and is connected with a building just by roof (rafters + timber sheating).

Would you design this frame as a moment frame or not?

Im thinking that RC frame is going to be loaded only verticaly hence no need for a moment frame. All horizontal forces (wind, earthquakes) will get transfered to the structure inside the RC frame, since frame is connected to this structure by roof (i thinkg rafters + sheating on top will act as diaphragm which will transfer horizontal loads from RC fram to building).

Because of that do you think there is a need to run rebars from columns to beam or is this not necesary since I dont need a moment frame? I think that columns will be sufficiently anchored to single foundations (Id design it as fixed supports) so columns kinda act as cantilevers anyway...

 

[atrizzy]

Is the concrete you show the primary lateral load resisting system? If so, you only have frames in one direction. The columns are cantilevered in the other.

 

[KootK]

As long as the building proper has it's own competent lateral system, I'd be happy to say that the concrete frames just go along for the ride. They'll see some nominal lateral loads but I think that's okay. They'll also have some nominal lateral load capacity. Of course, if you're high seismic, there'd be all kind of stuff to worry about like connecting the frames to the diaphragm robustly etc.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[BAretired]

Because of that do you think there is a need to run rebars from columns to beam or is this not necesary since I dont need a moment frame? I think that columns will be sufficiently anchored to single foundations (Id design it as fixed supports) so columns kinda act as cantilevers anyway...

I question the decision to use concrete columns and beams in a wood building but that is not what you asked. Whether you design the concrete frames to resist moment or not, it is simply good practice to extend column steel into the beams. If the structure is adequate to resist wind and seismic forces without reliance on concrete members, then designing moment frames is not essential.

BA