What is a full strength penetration weld? 2

[imsengr]

Hi all,

Can someone please elaborate on what a "full strength penetration weld"? I needed to specify some welding to join two pieces of a cut wide flange section. I was told to use a "full strength penetration weld". I would have thought something like a butt weld might work. What kind of a weld is it? Butt weld? Fillet? What does "full strength" and "penetration" mean?

Thank you much.

 

[csd72]

It is a full penetration butt weld.

If you call up a butt weld then it may only be partial penetration, so some people call up the full penetration bit to be sure.

 

[structuralaggie]

See table 8-3 in AISC steel manual. There are different types. Full penetration means the weld itself will at least be as strong as the steel sections it is joining together.

 

[jt12]

Doesn't full penetration refer to a weld the full depth of the material being welded independant of strength? My interpretation is penetration is the distance your weld extends below the plate surface. If your electrodes are stronger than your steel, you can probably get a partial penetration weld that is full strength (or of strength at least equal to that of the plate being welded)

 

[RARWOOD]

You should also post your question on the welding forum.

 

[structuralaggie]

jt12 - yes I agree with what you say too. Hard to say everything about a weld in two lines of text.

 

[Taro]

jt12, no that's not how it works. The strength of the weldment is the lower bound of the weld metal strength or the base metal strength. Even if the weld metal is higher strength than the base metal, it cannot develop the full strength of the connected part if is not full depth. The failure will occur in the base metal.

 

[henri2]

Interesting subject. I'd like to chime in with a few thoughts.

The first couple of pages in Part 8 of the AISC manual gives some brief explanation....and AWS A3.0 deals with welding terminology.

Butt weld is a non standard term for a groove weld in a butt joint; for instance, a bevel groove weld in a butt joint.

The term "full penetration" (FP) means complete joint penetration (CJP) as opposed to partial joint penetration (PJP)...Fig 8-22. In some cases, as pointed out by Jt12, full strength can be achieved without full penetraion. IMO, the term "full strength penetration weld" means, a CJP (FP) welded joint that can attain full strength. Dep[ending on the situaion, "full strength" does not necessarily mean "full penetration" is required.

Prequalified CJP and PJP welded joints are shown in Table 8-2...and if the proposed joint does not comply with the geometry in this table, then it will have to be qualified by testing, unless a WPS/PQR exists based on previous testing.

I notice that the sub-heading Available Strength on page 8-8, refers to Sec J2.4 and Table J2.5 in Part 16.1, pages 16.1-98 through 16.1-101. Assuming you'll be using a CJP welded joint, you'll be able to determine the required filler metal strength. Does this table provide information, to enable you to ascertain, if you'll achieve "full strength" for the situation you have?

BTW, does the coefficient C1 or some similar coefficient come into play in Table J2.5?

Will you be reviewing the fabricator's WPS?

 

[jt12]

You're right Taro. Sorry all. The weld material and the base material in a penetration weld mix enough in the heat that it would be wrong to assume a failure plane would be solely occurring through the higher strength weld material. If you want to guarantee full strength, it needs to be full pen.

 

[henri2]

Taro, good point. BTW, are there no situations where full strength can be obtained without a CJP groove weld? What of a lap joint, where members are joined using fillet welds?

 

[Taro]

Yes, fillet welds can be used to develop the full strength of connecting parts. But the discussion up to this point dealt only with penetration welds. And the fillet welds must engage enough of the section to preclude shear lag or block shear failure.

 

[henri2]

Thank you Taro