Fillet weld detail for Skewed T joint 1

[connectegr]

What is the "correct" detail for the attached skewed T Joint? The specifics are for plate thicknesses 3/8" or less, with an angle of 30* or less. A detailed root opening of 3/16" or less.

I have typically seen and provided the detail as shown in Option A. The other-side fillet weld is increased to account for the detailed root opening. Thus the fillet weld detail is shown with unequal sizes. This is also shown in the AISC 13th Edition, Table 10-13.

However, I am presently reviewing design calculations and details provide using Design Data's SDS2. The details are shown as Option B. The calculations refer to AWS D1.1 Figure 3.11. And the shop drawings show welds of equal size.

My concern is that with Option B the welder does not know that the weld size shown are effective leg sizes. And that much more than a single pass weld is required.

http://www.FerrellEngineering.com

 

[racookpe1978]

Couple of issues:

The lower fillet - that portion of the weld below the 3/8 thick plate - cannot be "accessed" by the welder since it is only open at a thirty deg angle. (Imagine a 30 degree weld prep 3/8 deep - you can't reliably melt steel down in the bottom of that tight a grove.

On the far side, the opening is bigger (60 deg) but that's only marginal for a fillet weld.

Better weld prep is to open the back side a little bit by grinding the bottom of the plate to at least a net 70 deg angle: then you can really assume your 1/2 inch weld is really a 1/2 inch weld. (The filler metal will actually be joined on both sides.) Easiest is to specify a 45 deg angle on the bottom of the plate - the fab shop won't screw up with the angle calc and you'll get an easier 75 deg opening.

 

[DVWE]

If you can get a copy of AWS A2.4 - Standard for welding symbols, there is a complete section in there on how to properly detail skewed joints such as this.

 

[connectegr]

Racook
The intent is not a groove weld. The fillet weld is increased to lap the opening.

http://www.FerrellEngineering.com

 

[gtaw]

The term fillet weld is applicable to welds deposited on the joint with dihedral angles between 80 and 100 degrees. If the dihedral angle is less than 80 or more than 100 degrees it is a welded skewed T-joint.

For angles between 60 and 80 degrees the designer has to account for the effective throat using the formula contained in Annex B (D1.1-2006 as an example). For angles between 60 and 30 degrees the designer must allow for the Z-loss and for angles less than 30 degrees, the designer cannot consider the weld capable of transmitting load.

The designer (Engineer) is responsible for specifying the effective throat when the dihedral angle is le3ss than 80 degrees; the detailer must provide the shop details depicting the required leg size (including Z-loss where applicable).

A standard welding symbol is not appropriate for skewed T-joints, since the fillet weld symbol specifies the leg size and assumes there is fusion to the root of the joint. It is more appropriate for the welding symbol to reference a detail of the joint in the tail. The detail should depict the joint cross section with the appropriate dimensions so there is no question of what is required. That being the case, the welding symbol can consist of the arrow pointing to the skewed T-joint, a reference line without a weld type specified, and the tail with the appropriate detail listed.

At least, that is what I would do.


Best regards - Al

 

[hokie66]

Agree with gtaw. As shown in the sketch, it's not a fillet weld.