Steel to Wood Connection Design Help Needed...

[rulljs]

I work mainly in the structural steel world so the steel analysis of the attached sketches is not a problem, when it comes to the interaction with the wood is where I get a bit confused.

I believe my main concern with this connection would be the bolts ripping/tearing out of the wood, (as long as all the steel strengths are adequate to carry the load), but I'm not sure how to find out how much load can be put on the bolts before the wood fails.

I've attached two .pdf files, (tried to at least) to further detail the situation I have. Any input will be appreciated.

Thank You.

 

[rulljs]

Looks like only one .pdf got attached...here is the other view.

 

[PSlem]

Nat'l Design Spec for Wood Construction from Amer. Wood Council This will give numbers. There are several failure modes to be checked.

 

[Lion06]

Do you have a copy of the NDS?

 

[Lion06]

I would also note that your loads (which I'm assuming is only one load) are perpendicular to each other.

 

[Ron]

A couple of questions first...

1. Why is the steel section in there to begin with? Is the wood column existing and too short? Are you modifying something or is this new construction?

2. From a design standpoint, this creates a potential lateral load deficiency, with as you suspect, high bolt loads depending on the magnitude of your lateral load.

You can find all the allowable loads for the wood and the fasteners in the National Design Standard for Wood (NDS). If you do not have a copy, you can purchase electronically from the American Forest and Paper Association.

 

[rulljs]

I do not have a copy of NDS.

The reason for the steel section is for aesthetic purposes only.

One side note is that I am not the engineer responsible for this design, it is something that has been built already and it looked a little suspect to me so I just wanted to run some numbers to convince myself that it is structurally sound. I have been assured that this has been looked at by an engineer, but again, the design looks a little suspect to me and I just wanted to run some quick numbers to see what loads it is capable of handling.

 

[rulljs]

StructuralEIT

The loads shown on the sketches are depicting two different load scenarios...wind from the East and Wind from the South.

 

[JAE]

The NDS provides minimum edge distances from center of bolt to edge of wood. You don't provide those dimensions on your sketches and these might be critical checks to do.

Is there a cap plate on the 4x4 tube? I would think so as the welds you show between the upper "U" bracket and the 4x4 would be little welds on the tube wall edges otherwise.

 

[rulljs]

I should have posted pics the first time, they may paint a better picture...here is the first of four.

Note, all vertical bracing shown is only temporary.

 

[rulljs]

Second.

 

[rulljs]

Can anyone see the first two pictures, I cannot see them when I click on the link. They are in .bmp format.

 

[JAE]

I can't see them - the file that comes up on Engineering.com just has the word "pic" instead of a usual filename.jpg.

Are you uploading jpgs?

 

[rulljs]

.bmp and .pdf files seem to not be working, here is a try with a .jpg file, if this doesn't work I don't know what else to try.

 

[JAE]

You must be uploading it wrong - every file that Engineering.com refers to in your posts says "Pic".

Why don't we see .jpg or .pdf? Are you browsing to the correct file?

 

[hokie66]

Still nothing.

 

[rulljs]

ok..maybe no pictures until I can figure out how to post them correctly.

Before I post the attachment has the full name with the extension (.jpg/.bmp/.pdf) but once it gets posted it just says pic?? I may have to post pictures through a third party picture hosting site which I cannot do right now but may be able to do in a few hours.

 

[apsix]

Try converting pics to pdf and upload again.

 

[BAretired]

If you are attempting to create a moment connection between the wood beams and the 4x4x1/4 tube, you need to be concerned about the distance from the bolt to the edge of the wood member which, as you have shown it in "Looking West" appears to be much too small.

BA

 

[msquared48]

I cannot understand why a moment connection would be required here to resist the lateral load with this connection. That should be resisted with some other element regardless of the direction of the load.

That being said, I do not like the connection at all as it is a hinge connection in a column, inherently unstable, regardless of the length of the tube column. The wood column should have been extended to the underside of the beam and framed with a beam to column hanger.

Sorry to say, but this appears to me to be an example of an archectural detail gone awry and unchecked by a structural engineer.

Mike McCann
MMC Engineering