MITERED BEAMS AT CORNER

[Sokka10]

Hi all,

I worked on a plan with two 5 1/8" x 15" glulam beams coming together over a 6x6 post at a covered patio. Each beam has a load of about 5 kips. I called out one of these bad boys on the plans to attach the beams to the post (picture on the left). Instead, the builder would like to miter the beams at 45 degree angles and join them together like this (picture on the right). My questions are:

1) What implications are there for beam shear and end bearing length with a miter cut? I can't find anything on this topic, but it seems to me that shaving off a fairly large portion of a beam at it's bearing location would significantly impact its shear strength?

2) How would you normally detail a connection like this? I like the Simpson caps, but I imagine there are a bunch of acceptable solutions.

 

[dik]

A mitred corner may look OK, but it is possible that one of the beams is load carrying and the other is not. I think it would be best if the load carrying beam was fully supported. Not a wood guy, but my thoughts.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Sokka10]

Thanks, dik. On this particular project both of these beams will be load bearing. The covered patio has a large hipped roof so both beams will be carrying some of the weight of the patio roof.

 

[Harbringer]

I doubt you will have an issue with shear. Is each beam reaction 5k?

Obviously your bearing area would decrease. You can check that maybe with H/3 of the triangle neglected.

As shrinkage occurs this miter will open up. What does the col cap for the miter look like on the inside?

How are you detailing the hip connection? Will movement of the miter negatively impact that connection?

The miter brings up some possible problems of beam stability and detailing more than a calc issue imo.

 

[XR250]

10k is a pretty hefty load on top of a 6x6. I would stick with you original plan or use an 8x8 post. I'm sure that hardware is expensive but so are the glulams.
What is the demand/capacity for the 6x6?

 

[Sokka10]

The column is 9 ft. tall, DF-L #2. I'm getting an axial compression capacity of around 17 kips. Plan is to tie the lateral wind and seismic into the back wall of the house through the roof diaphragm so no lateral loads or uplift on the column