Maximum Weld Size for 1" plate connected to .465" HSS tube

[amain002]

Hello everyone,
I have a question which is kinda debatable. I have a 1" plate connected to HSS column with 0.465" thickness. The AISC specs says that the max weld size is 1/16 less than the plate size which in my case can go upto 15/16" weld size. In my analysis I need 1/2" weld but since my column thickness is less than the weld size is it OK to use it? I am not sure but can we use a weld which is larger than the base metal. Please provide me with a suggestion. A reference will be a bonus.

All you response is appreciated. Thank you in advance.

 

[msquared48]

Just put in a 1" thick backer plate inside the tube and use the larger weld.

Mike McCann
MMC Engineering

 

[jdgengineer]

I don't think there is any magic to maximum weld size as a relationship to material thickness. Check the strength of your weld fracturing at the weld and check it fracturing at the base metal and see which governs. With an HSS tube you should be able to develop a weld thicker than the base metal.

The 1/16 requirement for plates 1/4 or larger is intended to give a way to visually observe the thickness of the weld. I believe the concern is that if you weld right to the edge of the plate that it is possible to melt the edge of the plate and give the illusion of a thicker weld. This requirement only applies when welding across the thickness of the plate.

 

[racookpe1978]

If the HSS wall thickness is 0.465, why do you believe that a 1 inch (or 15/16 inch) weld would deliver more strength than the 0.465 wall?

For fillet welds at a right angle joint, the maximum available (well, useable) thickness is the thinner of the two wall thickness of the two metals being joined.

 

[gtaw]

The maximum weld size quoted in this post (1/16 inch less than the plate thickness) is relevant to lap joint only. It does not apply to T-joints, skewed T-joints, or corner joints.

There is a limit on the unit stress to prevent over matching the filler metal. For example; in the case of a fillet weld, the unit stress in shear is .3 times the tensile strength of the filler metal, but the unit stress on the base metal must be less than .4 times the yield strength of the base metal.

Best regards - Al

 

[jdgengineer]

Sorry if my post was unclear. I don't believe you can develop a 1" weld with a .465" wall but I do believe you can develop a weld thicker than .465".

Strength of fillet weld is Fw x Aw. Strength of base metal is Fy x Abm. If Fw is .7 x 70ksi = 42ksi and the tube Fy = 46 ksi you should be able to get a thicker weld than the base metal. The Aw for a fillet is also at .707 x tweld so you also get more effective base metal area.

 

[jdgengineer]

Sorry 0.6 not 0.7.

You also would need to use strength reduction factor or omega for ASD as required, but concept is the same.

 

[jdgengineer]

I suppose I may have also incorrectly assumed that the op was talking about a fillet weld and not a groove weld.

 

[amain002]

So, is the conclusion yes we can use a weld size larger than the base metal size. I have attached a image below to have a clear understanding of what I am referring too.

For now let say I have a tension of 65 kips.

Weld strength for 6" wide plate, using 1/2" fillet weld

= 0.928 x 8 x 6 x 1.5 (since load is at 90 degrees) = 66.816

Min thickness required = 3.09D/Fy = 3.09 x 8 / 46 = 0.537 which is less than the base metal thickness.

What else do I need to check, Please provide me some suggestions. thanks

https://gm1.ggpht.com/Jju-Xmk6wVgg6...K3NKzFT-yGR40V4kTv3HlVOiyGKoVc=w1163-h748-l75

 

[gtaw]

The link wouldn't work.

Best regards - Al

 

[amain002]

I am sorry, please disregard the link. I cant find a way to upload a picture.

 

[BAretired]

Store the picture in a file on your computer, then upload the file in Eng_Tips.

BA

 

[zcp]

Save yourself some headache and get some more weld length. You need 1/2" thick as configured, yet your base material is 0.465".
Be conservative with welds. Check out AWS to see how undersize they can be for what length of weld. See some field 'welding'. And remember, members will warn you before they fail...connections will not.

ZCP

http://www.phoenix-engineer.com

 

[dik]

If it's like a base plate, then I would run with 1/2" max weld and ignore the 1/16 th smaller... CIECT has testing information that if weld size is increased to approx 10% or the tube thickness, the equivalent of almost a full pen weld is achieved... If you creep beyond code requirments you're on your own... as I had one Judge's written judgement... "...Mr. Coates' cavilier applicaion of the Ontario Building Code..." I wear that badge with honour...

Dik

 

[gtaw]

Once again, the weld size limitation of 1/16 inch less than the base metal thickness for thickness of 1/4 inch or more pertains to lap joints only if working to AWS D1.1 requirements.

Best regards - Al

 

[amain002]

Alright found a way to upload a pic. Attached please see the link for the pic.

https://www.flickr.com/photos/125092832@N03/14537578376/

at zcp, the size of the plate is 6" so I cannot get more weld length.

For now let say I have a tension of 65 kips.

Weld strength for 6" wide plate, using 1/2" fillet weld

= 0.928 x 8 x 6 x 1.5 (since load is at 90 degrees) = 66.816


Thank you for you help.

 

[racookpe1978]

Your drawing (tension on bottom, compression on top) means that the load is pushing "up" on the beam? Did you mean that?

You don't seem to understand my previous concern: A simple fillet weld cannot be stronger than the thinner of the two plates joined at right angles. True, the thick fillet weld will not fail. It will pull out the wall of the vertical HSS out of shape, perhaps completely off of the vertical member.

 

[BAretired]

The weld is not really 6" long because of the corner radii of the HSS. Assuming an exterior corner radius of 2t, the actual length of weld is only 4".

The HSS wall is not capable of carrying the line load in bending, across the width of the HSS, so the bottom weld will tend to crack at the extremities which will then propagate toward the middle of the weld with a risk of premature failure.

The bearing at the top of the 1" plate is problematic too if the HSS wall cannot span across the 6" width so the force is delivered from plate to HSS by two concentrated reactions near the corner of the HSS. This could be mitigated by filling the gap with weld metal at each corner, but such a weld would require special procedures.

BA

 

[gtaw]

Try reviewing AWS D1.1-2010, clause 2, part D. It addresses the design parameters for tubular connections.

Best regards - Al

 

[zcp]

If the plate is 6" wide, you can run a flare bevel up each of the vertical sides. Then have 4" fillets across top and bottom as BAretired correctly noted. Do not connect the welds. If that does not get you enough, redesign the joint (brace it, add angles, box the tube, etc.).

what size is the Wbeam? why are you trying to make a moment connection here?

ZCP

http://www.phoenix-engineer.com