What is preferable to place: 3/16" or 1/4" fillet weld?

[StructureMan44]

What's preferable for a steel worker to place; 3/16" or 1/4" fillet weld?

We're attaching auxiliary steel to existing building steel to support some lightweight pipe (<1 kip at most support points). For our application either size is sufficient as 3/16" fillet weld provides 4.2 kips/in strength capacity for longitudinally loaded weld and 6.3 kips/in for transversely loaded weld.

 

[MotorCity]

Either could be made in a single pass. The 1/4" would take a little more time, but I would not think it makes a difference to the welder

 

[SlideRuleEra]

From AISC Modern Steel Construction Magazine, February 2013, article "Blodgett's Treasures":

For economical designs, it is preferred to make fillet welds smaller in size and longer in length; smaller fillet welds generally provide economy over large fillet welds. Why is this? Because the weight and cost of the weldment increases by the square of the leg size of the weld. Thus, savings in the weight of the weld metal for each weld and the arc time it takes to make each weld can be achieved by specifying the smallest, longest fillet weldment. Not only are there savings but the smaller, longer welds also help reduce heat input and the distortion of the base metal. It’s a win-win!

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[JGard1985]

Have to love Blodgett! So much knowledge

But does anybody have a copy with a table of contents? I have a copy but it seems like they forgot a table of contents

Anybody have a place to download and print a table of contents of "Design of Welded Structures"



Jeff
Pipe Stress Analysis Engineer

http://www.xceed-eng.com

 

[UcfSE]

You can still buy the books it seems, fairly cheap.

http://www.jflf.org/SearchResults.asp?Cat=81

 

[KootK]

But does anybody have a copy with a table of contents?

TOC attached.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[JGard1985]

Perfect

Thank you so much!

Jeff
Pipe Stress Analysis Engineer

http://www.xceed-eng.com

 

[racookpe1978]

Well, there is another thing to consider between the two weld sizes.

I'm going to exaggerate a little here.
Assume you have a bad welder who varies the weld leg randomly 25% up and down for a 1/4 inch lengths of weld bead.

A 1/4 fillet weld is 2 inches long, with two parts 25% too high (5/16 leg), and two parts 25% too low (3/16). You have two sections of a short weld significantly under strength.

The 3/16 weld is longer than the 1/4 weld (by at least 6.3/4.2), but has smaller variations in leg height over a shorter total length of bad weld.

But that same bad welder may also try to go too fast on the smaller weld and not get a much penetration into the base metal.

 

[Once20036]

I would never disagree with Blodgett, but I wonder how applicable his wisdom in current economic conditions.
He indicates that due to the cost of the weld filler material, a long thin weld is more economic.
It seems to me that labor has a more significant impact that the materials, and a short thick weld would take less time, and therefore be the more economic option.

Ultimately, either weld is a single pass and I think we're wondering about pennies here.