Joist-to-Beam Connection at Overhang 1

[Edward99]

Hello All,

I am new to the eng-tips forum, and I am a relatively new engineer in training.
I am working on the structural design of a commercial office building. Refer to the attached PDF to view the structural model (in progress) for context.

As you will see, the entrance features a slopped roof with LVL roof joists that overhang over the front elevation (approx. 1.8 m overhang). The overhang is needed for a large soffit assembly that was added by the architect for aesthetics.
In the current configuration, the roof joists bear directly on a steel beam in the front elevation wall (see attached PDF). I've analyzed the joists as pin-pin (with the perpendicular steel beams as supports) with an overhang as shown. I've also taken into account the snow drift load that will form due to the higher performance wall.

I am concerned about the joist-to-beam connection at the overhang area (highlighted in yellow in the PDF). I’ve calculated a large upward reaction force at this location. I'm uncertain about the ideal connection for this, it might need a more specialized connection than a standard hurricane tie. I would appreciate any thoughts or suggestions regarding the overall configuration and the type of connection that would ensure stability.

Thank you for your help.

 

[SE2607]

What is the net uplift force?

 

[dik]

and a line of solid blocking between joists at the support beam as good construction practice.

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

-Dik

 

[Edward99]

The upward reaction at the overhang support is 25 kN (factored).

 

[SE2607]

The upward reaction at the overhang support is 25 kN (factored).

That's about 3,500 lbf/joist (ASD)! Sorry, I'm not that accustomed to SI units (25x0.224/1.6?). Is that per joist?

 

[dold]

I've dealt with these things before. This is a rough idea of how we handled it.

 

[Edward99]

That's about 3,500 lbf/joist (ASD)! Sorry, I'm not that accustomed to SI units (25x0.224/1.6?). Is that per joist?

Yes that is the upward reaction at the support where the joists bear on the steel beam for each joist. I believe it would convert to a 5,620 lbf upward reaction force at that support for each joist.

 

[SE2607]

Yes that is the upward reaction at the support where the joists bear on the steel beam for each joist. I believe it would convert to a 5,620 lbf upward reaction force at that support for each joist.

My first recommendation is to check your loads. My second would be to check the joists. I do realize you are dealing with Cg for overhangs, but that's quite a bit of load for a rafter.

 

[Eng16080]

...that overhang over the front elevation (approx. 1.8 m overhang)

I’ve calculated a large upward reaction force at this location.

I believe it would convert to a 5,620 lbf upward reaction force at that support for each joist.

I don't think your loads are correct, unless you're designing this for a tornado!

Using our (stupid) American units and looking at your rendering, I estimate a tributary area of roughly 24 square feet going to each joist support (at the overhang). So, that amounts to a net uplift of about 230 psf. This is roughly 5 times greater than what I'd expect the uplift force to be.