is this timber roof horizontaly stable?

[kjG87]

Hello. This is not my field so I hope for some help and suggestions.

My question: Is this timber roof horizontaly stable (in case of wind/earthquake forces)?
In longitud. direction I know this is stable since we have knee braces + sheating on top of rafters that transfer forces to longitudinal walls and RC slab.
But what in other direction? Walls are masonry + RC ties. I dont want any bracing between columns (in vertical plane) because I need space between.

In attached file:
rafters - brown
knee braces - red
column/post - blue
longitud. timber beam - yellow
collar tie - green

 

[dik]

It can be... depends on connection design. Framing is common to 1000 timber framed barns. Tie the roof into the end walls.

If you raise the interior columns you get the classic Gabriel roof line.

Dik

 

[msquared48]

Agreed. A skip-sheathed roof diaphragm could be dicey, but plywood could be no problem.

Mike McCann, PE, SE (WA)

 

[LittleInch]

Or a brace from the brown timbers to the middle of the green one on both sides, intersecting at 90 degrees or so, maybe every second or third would add a lot of strength to the frame?

Kind of like this

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[cal91]

It is an indeterminate, stable structure.

Nrx = number of support reactions = 4
Nl = number of closed loops = 4
Nh = number of hinges = 11

 

[dik]

LittleInch:
By bracing on an angle, it reduces the available floor space above... It can be worked to be a stable structure with vertical wall elements. Common timberframe 'barn' structure...

Dik

 

[LittleInch]

dik,

I meant between the green beam and the brown beam in the OPs original post (not the knee brace on the post). I got the impression the floor space he wanted to use was in the bit below the green beam?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[oldestguy]

You fellas are missing something. Add plywood or other sheathing and you have a significantly different structure. I suspect this is not a tent with cloth for the roof

 

[dik]

LI... thanks

Dik

 

[BAretired]

The structure as illustrated, relies on the masonry walls in bending to resist lateral loads. It also relies on connections at various points.

Edit: Adding braces between the brown and green members as suggested above, does nothing to change this.

BA

 

[DaveAtkins]

I disagree with BAretired. If there is roof sheathing, the lateral load is resisted by the roof and the floor.

DaveAtkins

 

[BAretired]

DaveAtkins makes a good point. If the roof and floor deck are capable of behaving as diaphragms spanning the full length of the building, lateral load could be resisted in that way, but the structure, as illustrated, relies on bending of the masonry walls.

BA