Weld size for double sided fillet weld 2

[kaffy]

Good Morning fellow engineers,

I am looking for information on double sided fillet weld. I understand that there is a minimum size of fillet weld based on thickness of the part when it is a single sided fillet weld based on codes.
Also, I read it somewhere that we should avoid welding on both sides of the plate due to heat affected zones.

I have a T shape made out of plates ( 1/2" plates) file attached. I can size the single side fillet weld based on load requirement but I would like to use double sided fillet weld (obviously smaller weld size as compared to single side fillet weld). But as the plates are only 1/2" thick, I am not sure about HAZ.

Is there any reference showing the smallest size of double side fillet weld for 1/2" thick plate or showing the HAZ depth for different size of welds?

Thank you
Newbie

 

[ProgrammingPE]

Double sided fillet welds are extremely common. If you have a single-plate (shear tab) connection, then the connection plate is fillet welded on both sides to the support. It is also good practice to use double sided fillet welds since any tension or shear in the plate will go equally to both sides which prevent any eccentricity.

The minimum sizes for fillet welds is the same regardless of if it is welded on both sides or just one side.

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[dauwerda]

I agree with everything ProgrammingPE Stated.
If you are following AISC 360 (steel manual) the minimum fillet weld size for 1/2" thick plate is 3/16" (Different codes will have different requirements as will different materials). The size of the HAZ will be affected by welding process as much, if not more than, the size of the final weld.

 

[dhengr]

Kaffy:
The min. fillet weld size vs. pl. thk. is to assure that there is enough heat input during the weld process, given the pl. size/thk. heat sink potential, so as to control the HAZ in reasonable metallurgical condition. To little heat input causes the weld and the HAZ to be brittle and have poor metallurgical properties, due to quick solidification and cooling. Double sided fillets are almost always better because they are balanced/symmetrical, in terms of picking up the loads/stresses from any eccentric loading on that web pl. of your ‘T’. You do not want a force perpendicular to the web pl. causing tension (prying) across the root of a single fillet weld, and the double weld minimizes this potential. On pl.#1 you should stop your double fillet welds short of the edge of that pl. Then on pl.#2, a gusset or stiffener, you should clip the back corner at 45° so it misses the web fillet weld. Stop the welds on pl.#2 short of the edges also, and don’t weld into the corner at the web fillet weld. Welding into that corner causes nasty triaxial stresses and residual stresses from the welding shrinkage. Welding around the edges/ends of pls. almost invariably leaves nasty notches and stress raisers, which we do not want either.

 

[kaffy]

Thank you very much.Really helpful