timber scissor trusses

[JMASE]

Architect wants to build a 60 ft. long by 20 ft. wide open plan (no interior walls)structure. The short direction roof will be broken up mid span with clerestory windows. It will be framed with custom timber scissor trusses. What's the best way to handle scissor truss thrusts and take the wind loads to the end walls?
Thanks

 

[Greenalleycat]

Hah, classic architect, I've dealt with a few of these

Once I get sufficiently nervous I tend to stick plywood ceiling diaphragms in and make sure they're well anchored into solid end walls
Typically in these sorts of structures (here anyway) the internal end has some sort of bulkhead drop down to the kitchen so you have a standard truss
I line this with plywood vertically and spec a ribbon plate to connect the ceiling diaphragm into the sheathed truss
At the other end there's typically a big wall of glazing, usually requiring a pitched portal frame
Hopefully you're able to run a steel tie beam across at the knee as this is required to support the glazing - this prevents spread of the portal so you just need to sort the connection of the diaphragm into the portal

Other options include using intermediate steel portals to break up the ordinary (non diaphragm) ceiling span, or getting real fancy with your top plates to have large out-of-plane bending stiffness
Buttressing walls in other areas of the house can help too, though usually scissor truss ceilings are over 'wings' so this effect isn't presenet