Connection over stressed.

shacked · Dec 7, 2022

I have an existing condition that I am trying to work out and make work.

Existing single story light framed house. Roof is 4x10 beams spaced @ 7ft o.c. & 2x T&G spans between. See attached picture of the connection between each 4x10 beam at the ridge point.

Architect wants to install 2x10 framing over the top of the existing 2xt&g & 4x10 beams. The new roof will continue up past the ridge line as a shed roof.
(As you look at the picture roof continues up to the right)

This is only a problem at one location in the house(living room) The actual shear is greater then allowable by about a factor of 2.

In order to make this connection work I was considering two 1/4" thick steel plates, one each side of the 4x10 in order to increase the section modulus for greater shear resistance. Any thoughts? I rough sketched the plate on the picture.

Trying to determine how to analyze this. Could I assume that both steel plates cantilever past the support bolt group on the right beam, therefore creating a moment that has to be distributed through the bolts/beam?

Thanks Erik

dik · Dec 7, 2022

A bad connection... load is highest where the member is 'thinnest' and minimises where the member is 'deepest'. I'd think steel side plates would be one of the 'only' solutions. I'd go for glulam rivets and not bolts. It appears to be sawn timber, so shrinkage cracking could be an issue.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

phamENG · Dec 7, 2022

Interesting. I'd be really careful with it - looks like the connection is already trying to rip itself apart as is.

I agree with dik - if timber rivets aren't common where you are and it won't be visible, using many screws would be a good alternative.

Factoter · Dec 9, 2022

That’s an unusual design, not very slightly either to my eye. . . was the paint sandblasted?
Since another layer is being added, place your reinforcement plates on top and bottom, that’s the natural strength of the joint anyway, one big ole scarf!

driftLimiter · Dec 9, 2022

Is that member on the right a propped cantilever or it is just a moment connected leg of a single beam on the left?
If the ladder it seems like the segment on the left is already just ignoring the segment on the right and simply bearing on its tiny little toe.

Might consider sucking that crack closed from below with some timberlok screws. Could use them to resist tension and shear if needed.

kipfoot · Dec 11, 2022

I don't have a lot of hope for your connection, but maybe it will work in your case. Getting reasonable fasteners to work in the space available always seems to be a challenge.

Can you configure the over-framed portion in a way that makes the issue go away by placing the roof load directly over the beam?

BAretired · Jan 6, 2023

If beams are placed as shown below, I don't see a shear problem. The new beams will bear directly on the existing girder.

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Connection over stressed.

shacked

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