Checking the base material in a tension welded connection?

[StructureMan44]

If I have a tension connection consisting of a gusset plate fillet welded to a 6"x4" angle with welds in the longitudinal direction along the edge of the 6" side of the angle and the corner of the angle, it seems AISC 360-10, Specification for Structural Steel Buildings, gives conflicting advice. The two areas of conflict are:

Section J 2.4: "The design strength of welded joints shall be the lower value of the base material strength determined according to the limit states of tensile rupture and shear rupture and the weld metal strength determined according to the limit state of rupture..."

Table J2.5 for fillet welds it says the base metal is governed by section J4. Section J4 recommends checking (J4.1) tension rupture AND yielding and (J4.2) shear rupture AND yielding.

Assuming the base material is whichever (gusset or angle) has less cross-sectional area, my question is, does the base material need to be checked for tension and shear yielding in addition to tension and shear rupture?

 

[StructureMan44]

Bump for any help from the experts here at Eng-tips.

 

[JoshPlumSE]

I think the AISC 14th edition manual equation (9-2) on page 9-5 gives some explanation / clarification about what they're really looking for. At it appears to be rupture of the base material, not yielding.

 

[StructureMan44]

Thanks JoshPlum.
Page 9-5 directs you to section J4.3 of the commentary which gives equation J4-5. This equation compares the limits state of shear rupture/tensile rupture on the left to shear yielding/tensile rupture on the right. I guess a better question than the original one I asked is it safe to disregard tensile yielding in all block shear checks?

 

[JAE]

Section J2.4 lists the design basis for ALL types of welds, not just fillet welds.

I guess I would see it like this: Table J2.5 has a specific requirement listed for base metal checks with fillet welds - "go to J4".
This seems to over-rule the language in the first paragraph of J2.4.

J4 requires both checks (yield and rupture) for the base metal.

Section J4 is used for both welded and bolted type connections so they include both checks - one with rupture across an effective area (smaller than Ag because of bolt holes or weld geometry with the U factor - see Table D3.1), and one with yielding on the gross area.

I would check both.

The manual equation 9-2 on page 9.5 is only for shear in connecting elements - not tension.




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[JoshPlumSE]

JAE -

I'm not so sure. The section is titled "Connection Element Rupture Strength at Welds". So, I think page 9-5 does apply. Maybe not equation 9-2 directly, which is clearly shear. However, the concept of how they came up with equation 9-2 can be extended out to cover tension welds as well.

StructureMan -

I'm not talking about the "Connecting Elements Subject to Block Shear", but rather the next section. The one titled "Connection Element Rupture Strength at Welds". To me, this section is a direct attempt to clarify the code provisions related to base material rupture as required by J2.4.

In my opinion, the yielding of the Base material is probably a valid limit state as well. However, it is not subject to the lower phi factor that is associated with weld capacity. Haven't we all seen the pictures of the northridge moment connections where rupture of the base material occurred right at the weld interface? My impression is that this is the type of failure they're hinting at when talking about base material in the weld capacity section.

 

[JAE]

Josh - the equation 9-2 is for shear only. Look back to page 9-4 for the tension section. The equation 9-2 has a 0.6 factor in it that only applies to shear conditions.

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[StructureMan44]

Is there one limit state that can be eliminated; if order for shear rupture to occur, tensile rupture must occur? Can this be understood physically as in order for movement along the vertical line of bolts to occur (shear rupture) the area in tension has to break or move apart in order to allow the shear rupture movement to occur? Maybe this explains why AISC doesn't consider tension yielding in equation J4-5?