Minimum fillet weld size, 3/16ö or +ö

[J1D]

In fabricator’s connection shop drawings, ¼” fillet (NS and FS) weld is specified to the weld between the web of W8x18 (0.229” thick) to a ½” thick end plate. In my view, the ¼” is not necessary here, 3/16” is good enough.

What do you think? Any harm to the steel connection if the weld is more than enough?

 

[samdamon]

J1D- What kind of loads do you have on the baseplate? Perhaps the load governs. Otherwise, the 3/16" fillet size satisfies the minimum size of fillet required by Table J2.4 in AISC manual based on the thickness of the baseplate.

 

[J1D]

Sam- The load is not a concern here. Strengthwise, 3/16" is more than enougth. The W8x18 is a beam, the end plate welded to the beam web is actually 3/8" thick.

I've used 3/16" as the minimum weld for structural connection for many year. Somehow I noticed some fabricators use 1/4" as the minimum anywhere now.

 

[samdamon]

J1D-

Perhaps he just doesn't want to change his welding set-up for the different fillet sizes. Are all of the other fillet welds in your project 1/4"? Regards.

 

[J1D]

Good point! But 1/4" is not the only fillet weld, 5/16" and 3/8" are used wherever required for strength. Also other types of welds have been used in the same package of steel structure.

 

[Lutfi]

Okay here is my two cents worth:

1. AISC 9th edition, table J2.4 Minimum size of fillet welds calls for a MINIMUM of 3/16 fillet weld if the material thickness of the thicker part being joined from 1/4 to 1/2. I would interpret this as being inclusive. Meaning that 1/2 inch would require 3/16 fillet weld.

2. The engineer should specify a fillet weld size should design and stress requirements are different from those AISC minimums.

3. I have seen many times where engineers specify ridiculous weld sizes that are very time consuming and expensive to the owners. I can speculate on why this is done.

4. I have also seen many engineers mislabel welds and their call outs. AWS publishes a book on the weld symbols and the proper way to use them. I recommend to every SE to have one on his or her shelf.

Regards,


Lutfi

http://www.cdeco.com

 

[desertfox]

Hi j1D

Although I don't need to follow the AISC weld specifications.
The rule of thumb I use is that the maximum size fillet weld allowable is the minimum plate thickness of the parts being welded.
However if you use a larger weld than is required then your heat input is increased and distortion of the welded parts also increases.


regards desertfox

 

[jheidt2543]

REF: "Steel Structures, Design and Behavior" by Salmon & Johnson, Intext, 1971, p. 192

Minimum Fillet Weld Sizes:

MATERIAL THICKNESS OF MINIMUM WELD SIZE
THICKER PART JOINED (in)
(in)

Up to 1/4 inclusive 1/8
Over 1/4 to 1/2 3/16
Over 1/2 to 3/4 1/4
Over 3/4 to 1-1/2 5/16

According to AISC the above fillet weld sizes are governed by the THICKER of the two pieces being jointed, except that the weld size need not exceed the thickness of the thinner piece unless a larger size is required by calculated stress.

The maximum weld size is limited to the thickness of the THINNER part jointed.

 

[DRC1]

It depends on which rods he is using (assuming stick welding) Most welders perfer to have a 1/4" min. If you specify 3/16, they will often give you a 1/4" weld. Also if the weld has a little undercut, it could still be acceptable. Did you ask the detailer?

 

[J1D]

Thanks for the input! All are valuable.

Have a merry Christmas and a Happy 2005!

 

[Ron]

J1D...the fillet weld can be no thicker than the part thickness, so 1/4" fillet isn't "possible" here. In this case you have a 7/32" possible, though not necessary to specify to such a tolerance. If 3/16 is enough, specify that.

Remember....that which we measure with a micrometer will be marked with a crayon, then cut with an axe.

 

[HgTX]

Web to endplate is a T joint (no?), so the 1/4" is physically possible, and per DRC1, you may very well get the 1/4" unless you insist on a max size. I'm thinkin' you don't need to insist on a max size though.

Hg

 

[J1D]

HgTX- you’re right, it is a T joint between the web and the end plate, ¼” is possible.

For this particular connection, as per the discussion above, I believe 3/16” is the proper fillet weld size for engineer to specify. In general, I am reluctant to oversize the welds, not only for economy (smaller-longer is better than larger-shorter), also I concern the larger welds will have deeper penetration (burning) into the base material, which is detrimental to thin plates. The “lamellar tearing” (as described in AISC, ENGINEERING FOR STEEL CONSTRUCTION, a sourcebook on connections) is another concern.

 

[HgTX]

If you specify 3/16" and they happen to give you 1/4", it shouldn't be too bad, but don't ask me to tell you at what size you might expect a problem. (Ask someone else.) I'm assuming this is stick, not subarc on both sides simultaneously?

Have you asked around to find out how the 1/4" got there?

Hg

 

[yli]

Is this a highway project? If that is the case, you have to follow AASHTO Code. The minimum weld size allowed by AASHTO is 1/4" for plate thickness less than 3/4".

 

[HgTX]

Even in highway structures, the weld is not required to be any thicker than the thinner part joined, though they then warn about proper preheat. (The reason for the minimum size is because very small welds to thick steel are prone to cracking.)

Hg