Maximum thickness of fillet weld 1

[Ipetu]

A 1" thick cover plate is being welded to a HSS 8x8x1/4 (steel tube section). One reference stated that the governing material will be the thicker of the two (in this case 1" cover plate). The reference states that if the coverplate is greater that 3/4" then a 5/16" minimum fillet weld should be used. But does the 1/4" tube thickness not limit the maximum weld size to 1/4"?

Thanks

 

[dik]

Why 1" cover plate? Is this a cap plate that a beam is bearing on? You should be able to use either 1/4" or 5/16" weld. What is the reference?

Dik

 

[Ipetu]

dik,

the HSS 8x8x1/4 is a truss member that is 9 ft long. The 1" thick x 7" wide x 9 ft long cover plate is being used to strengthen the HSS member (i.e. add more cross sectional area to the HSS member). The reference is "Bridge Engineering, Design, Rehabilitation, and Maintenance of Modern Highway Bridges" by Tonias and Zhao.

 

[desertfox]

Hi Ipetu

Normally a fillet weld cannot be larger than the smallest material thickness.

desertfox

 

[MintJulep]

Unless your tube is some unusual section with square corners it's not a fillet weld.

 

[zcp]

AWSD1.1 table 5.8
note a...for non-low-hydrogen processes w/o preheat calculated....T equals thickness of the thicker part joined; single pass welds shall be used. For non-low-hydrogen process using procedures established to prevent cracking.....and for low-hydrogen processes, T equals thickness of thinner part joined; single pass requirement does not apply.
note b....except that the weld size need not exceed the thickness of the thinner part joined.
note c....min size for cyclically loaded structures shall be 3/16.

So you are looking at 5/16 or 3/16 depending on your electrode and process. Hope that helps.

ZCP

http://www.phoenix-engineer.com

 

[zcp]

Also, to expand on MintJulep.....any chance the plate could expand to 8" or more so you could have a flare bevel instead of trying to fillet weld right into the radius on the tube?

ZCP

http://www.phoenix-engineer.com

 

[weab]

Mint, I think that the plate is only 7" wide in an effort to avoid welding within the radius, though the end of the weld leg may fall into the radius.

I presume that the stated code is similar to AISC 9th ed. in that basing the weld size on the larger plate is due to proper heating. However enough heat to create a 5/16" weld may burn through a 1/4", so limit yourself to a 1/4". A good welder can do it.

I would agree with ZCP, though. I'd make the plate 8" wide and just do a flare bevel weld.

 

[paddingtongreen]

You are not going to get a fillet weld there. The edge of the plate is right at the tangent point of the curve, the HSS is curving away.

Without doing any calcs, that looks like a lot of area to develop at both ends of the 9' long plate.

Timing has a lot to do with the outcome of a rain dance.

 

[HgTX]

Even if it was a true fillet weld, the upper limit on fillet weld size really only apply to lap joints. For T joints, oversize welds might not be a good idea, but they're not outright banned.

http://www.modernsteel.com/steelinterchange_details.php?id=640

Hg


Eng-Tips policies: faq731-376

 

[gtaw]

You would have to reduce the cover plate width to about 6 1/2 inch in order to use fillet welds to secure it to the HSS. The alternative is to deposit a huge weld to maintain the required throat dimension.

Preheat would be based on the thicker member, but if you use a low hydrogen process the preheat for the 1/4 wall HSS and the cover plate would be the same.

The bridge code doesn't address tubular members, so D1.1 would most likely be the default welding standard. That being the case, the fillet welds would not have to be single pass if the low hydrogen welding process was used.

The fillet weld size is going to be limited by the (wall) thickness of the thinner member (HSS) so the weld doesn't fail by punch shear. I believe the allowable stress is .4 YS not to exceed .6 TS of either member. In other words a very large weld on a thin member is simply going to fail by pulling out a chunck of the thinner member with the attached weld when subjected to a high load.

Best regards - Al