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Base Metal Rupture - shear or tension

Base Metal Rupture - shear or tension

Base Metal Rupture - shear or tension

(OP)
We have a subtle issue with regard to AISC steel specifications.

We have a steel angle that is welded perpendicular to a plate. The angle is in direct concentric tension.

We are fillet welding the angle to the plate all around.

Under AISC specifications we have to check the following:
1. Weld rupture in shear
2. Base metal rupture.

We are OK with item 1. But under the AISC Table J2.5, the fillet weld base metal refers you to J4.

In J4, we have section J4.1 (Strength of Elements in Tension) and section J4.2 (Strength of Elements in Shear).

We are not sure which we should use, J4.1 or J4.2.
These are very similar except that J4.2 includes a 0.6 factor since it is dealing with a shear condition.

In looking at the steel angle it is all in tension so intuitively we think we should use J4.1.
However, in some textbooks and references we seem to keep finding the 0.6 factor creeping in. We can't find an example with this direct tension condition, though.

The argument for J4.1 Tension goes like this:
a) The angle is in pure tension.
b) Rupture of the base metal (the angle edges) would be a tension rupture.
c) The commentary for J2.4 (Page 16.1-339 in the AISC 13th edition manual) states "Tests have demonstrated that the stress on this fusion area is not critical in determining the shear strength of fillet welds". Therefore, the section for base metal to check is AWAY from the weld/steel interface and thus in a pure tension condition.
d) Therefore, the equation to use is J4.1 and NOT J4.2.

The argument for J4.2 Shear goes like this:
a) The fillet weld design is based on its effective throat in shear, thus the table J2.5 heading for the fillet weld is under SHEAR.
b) The check for the base metal is also under the heading SHEAR
c) Thus, the base metal should be checked in shear using the 0.6 factor.

Any help is appreciated.
We tend to think the J4.1 equations should be used primarily because of the commentary language.

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RE: Base Metal Rupture - shear or tension

Use J4.1, the tension check.

"But the weld is loaded in shear across the effective throat." If you want to check shear rupture of the angle, parallel to the load, the "thickness" would be the length of the angle. The weld is loaded in shear, but the plate elements are loaded in tension.

RE: Base Metal Rupture - shear or tension

For the angle, I would consider it as tension and use J4.1. For the plate, I would look at the manual section on Connecting Element Rupture Strength at Welds in part 9 (page 9-5 in 14th edition) for guidance. This section uses .06 Fu t.

RE: Base Metal Rupture - shear or tension

JAE....the fillet weld is as you noted...likely to fail in shear through the effective throat. The base metal will fail in direct tension. The penetration of a fillet weld into the base metal is insufficient to create a clear shear failure plane. I have cross-sectioned numerous angle to plate fillet welds and etched them to show the penetration. Solutioning between the weld and the base metal is relatively superficial, though good strength develops with a proper weld.

RE: Base Metal Rupture - shear or tension

I'd be curious to see the examples that check shear. That doesn't make sense to me but maybe I'm missing something.

EIT
www.HowToEngineer.com

RE: Base Metal Rupture - shear or tension

(OP)
Most of the textbook examples we've seen are dealing with things like single plate shear tab connectors (beam-to-column) where shear rupture checks make sense.
Not much out there for hanger/tension type connections.

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