Queen Post bottom connection questions

[Lennyzx11]

I have 2- 8x12 tie beams spanning 23 ft post to post with 30" knee braces that I plan on having 8x8 queen posts installed on. 
I mortised an 8"x2" mortise centered in the tie beam 5" deep and will peg the connection.
These queen posts are located at the 1/3rd marks of the tie beam. (8 ft in from each plate).

I deviated from the king post design of my original plan so this is uncharted waters as I had read and been told that the queen post truss would be stronger than the king post.

My question is would the connection as a whole be "stronger" if I did a thru mortise through the tie beam as I see a lot of queen post connections?

My reasoning for the only 5" deep mortise was to keep that tie beam from being cut into the least amount possible but the devil's advocate tells me that more relish and more pegs would make the connection stronger on the whole possibly.

Stronger in this case means to support that spanned length of Tie beam the best.

I did read some on the tie beam being weakened cutting into the compression or tension faces but I haven't figured out how to really get my answer.

Thank you for any and all comments.
Lenny

[Don P]

The queenposts are in tension, ropes, dangling from above and holding the tie beam up. One of the "rules" is the connections need to be on the opposite side of the neutral axis to avoid tension perpendicular to grain.

That was a mouthful. Tension perp, avoid it at all costs at all times, pulling apart or splitting wood by pulling on it perpendicular to the grain direction. This is the weakest direction in wood.

In a rectangular beam the neutral axis is going to be the centerline of height, usually compression above going from 0 at centerline to max at the upper surface. Tension from centerline to bottom edge again from ) to max at the lower strap... the extreme fiber. 

Sum that up, put the peg below centerline, the lower the better, below the beam is best. A steel rod thru the tie would do the least damage. Whatever the connection is it must be capable of resisting the tension force in the queenpost.

[beenthere]

A sketch of this design by Lenny would help this thread. tks

[Lennyzx11]

Like this beenthere.

Question was to cut completely through the tie beam with a through mortise or not.

I see DonP’s wisdom in getting the weight carrying points below centerline or even below the whole beam being better after explanation.



 
Lenny

[Don P]

I don't remember what is there content-wise but the Guilds truss series does include a section on Queenpost trusses. There is also their truss design guide...
dcstructural.com/wp-content/uploads/2020/09/TFEC-4-2020-Design-Guide-for-Timber-Roof-Trusses.pdf
That's just general stuff for review if you haven't seen it.
.. and that coat of water based poly oughta be dry, the puppy is saying let me stay inside on that tile floor 

[Chilterns]

Before giving any advice about whether or not queen posts work in tension or compression it would seem sensible to draw the cross section properly as the current rendition doesn't appear to make a lot of sense !

Queen posts can and do operate under both compression and tension depending on imposed dead weight and applied loading from snow, wind, etc.

More usually queen posts (or as now correctly renamed queen struts) are set inboard of the joint between the principal rafter and collar to provide space and hence relish between joints especially where clasped purlin joints are employed.

[Lennyzx11]

Before giving any advice about whether or not queen posts work in tension or compression it would seem sensible to draw the cross section properly as the current rendition doesn't appear to make a lot of sense !

Queen posts can and do operate under both compression and tension depending on imposed dead weight and applied loading from snow, wind, etc.

More usually queen posts (or as now correctly renamed queen struts) are set inboard of the joint between the principal rafter and collar to provide space and hence relish between joints especially where clasped purlin joints are employed.

The question was only about whether the tie beam to queen post was stronger with a through mortise or partial. DonP answered that.
Chilterns
I apologize the drawing didn’t “make sense”. It wasn’t meant to be an accurate cross section of a bent.
Lenny

[Don P]

I've looked a bit today and apparently never saved a link to Historic American Trusses and cannot find the 6 part series now. Queenposts were part II of the 6. It is available from the guild in book form but it was in collaboration with the Nat'l Park Service so it should be online free somewhere. If anyone has a link please post it.

[Jim_Rogers]

I've looked a bit today and apparently never saved a link to Historic American Trusses and cannot find the 6 part series now. Queenposts were part II of the 6. It is available from the guild in book form but it was in collaboration with the Nat'l Park Service so it should be online free somewhere. If anyone has a link please post it.

Here is the Historic American timber joinery link:
Historic American Timber Joinery, A Graphic Guide (U.S. National Park Service) (nps.gov)
But I think this is not what you wanted.
If you want to buy the book, here is a link to the site where you can buy it:
Historic American Roof Trusses | Timber Framers Guild (tfguild.org)
Jim Rogers
PS. to find a licensed timber framing engineer for NC go to: Timber Framers Guild - Enriching Community Through Craft (tfguild.org) and select "Find an engineer" and then your state. It will display a list of engineers. I used Joe Miller for my NC projects.