Collar tie removal

[Cruezr]

I have a client wishing to remove an existing post support under a "300 X 75 oregon ridge beam" which has lateral ties on both sides to the external walls (see image).
The ties on the right-hand side do not support any ceiling loads and are bolted to the sides of the existing beam via angle cleats.
The proposal is to bolt a new 400 X 75 LVL beam to the right-hand side of existing orgeon beam but requires the lateral ties to be temporarily cut and shortened, then re-attached to new LVL beam.
Roof pitch is about 21 deg on right-hand side (1 in 2.6 or 3 in 10.4), all existing timber is 30+ year old orgeon. Once the internal post support is removed, the new composite beam will span 6.1m (20 ft). and supports a sheet roof with plaster ceiling and highlight windows over.
I am concerned about stopping lateral spread of the external walls once the ties are cut and temporarily unattached to the ridge beam.
Any thoughts would be most appreciated.

 

[mike20793]

Is that a wall on top of the existing beam? If so, I'm not so sure you have a thrust you need to restrain. Thrust typically occurs when there is no support at the ridge.

 

[dhengr]

Cruezr:
I’d want to know a lot more about the existing details, workmanship, joint fit-up and stress grades of the lumber. I do not know what an “oregon” beam is. Let’s see a lot more dimensions, loads, joint details; are there posts under each right side rafter, do the rafters on the two sides line up at the posts, are these posts the vert. framing btwn. the clearstory windows, on down to the 340x75 beam, etc. etc. If the right side rafters bear on the ridge beam, double top plate (a horiz. seat cut bearing) then there won’t be much trust out at the right ext. wall. Put a few temp. diagonal kickers on the ext. of the building, up to the ext. wall top plate if you are worried. I would worry more about the header under these rafters and above the windows, are the windows operable. What’s the framing of the 3' high wall under the clearstory windows? If things fell into place properly, I would be tempted to try to make this 3' high wall, along with the 340x75 beam act as a box beam, or stressed skin beam spanning 20', and forget the LVL. Jack this wall up a little to relieve the loads (tension stresses) on the bottom chord (the 340x75 beam, which is continuous, I hope ), add some tight and properly designed blocking where needed, then glue and screw plywood sheathing, preferably to both sides of the wall, and release the jacks. You’ve built a stressed skin box beam out of the framed wall. Maybe put a couple light steel tensioned angles on the two bottom corners of the 340x75 beam.