Another HSS Flare Bevel Groove Question

By swnorris (****)

Date 11-06-2009 16:39

1. The effective throat of a prequalified BTC-P10-GF joint used to be 5/8 times the tube wall thickness. If the HSS has a 3/8 wall thickness, the "effective throat" (E) would be calculated .625 x .375 = .234 I don't recall which edition of the structural code this was taken from. I took it from the old green Ninth AISC/ASD Manual, which was issued in 1989.

2. I do know that the prequalified BTC-P10-GF in the 13th Edition AISC was taken from D1.1 2004. The formula is a little different, but the result is the same. The "effective throat" (E) has been changed to "total weld size" (E) and would be calculated at five times the wall thickness, divided by 8. I.E....... 5 x .375 = 1.875, divided by 8 = .234

3. The prequalified BTC-P10-GF joint in the current D1.1 2008 is based on the HSS radius. HSS radius is typically two times the wall thickness, but it could be more or it could be less than that. The "total weld size" (E) has been changed to "weld size" (E) and would be calculated at 5/8 times the radius. So, the HSS radius would have to first be measured in order to multiply it times 5/8. If the radius is 3/4", the "weld size" (E) is calculated at .625 x .750 = .468 This is in essence twice as much as in previous cases at .234

This is my interpretation of the current D1.1 prequalified requirement and I wanted to see how you guys would interpret it. Also...

4. There's the footnote "l" that states that the weld size (E) is based on the joint welded filled flush, but many times, the joint does not have to be welded flush to meet the design intentions. I think that in either case, the joint would still be considered prequalified, whether it's welded flush or whether the weld size is based on 5/8r. 2.3.1.4 also indicates that a flare bevel groove joint can either be filled or underfilled.

5. With regard to the "weld size" (E) being based on the radius, 2.3.1.4 indicates that for rectangular tubular sections, R shall be taken as two times the wall thickness, so, I would not be required to measure the actual radius of a rectangular HSS. I would only be required to measure the radius of square HSS.

By 803056

Date 11-06-2009 18:42

I believe most designers use 2T as the radius for sizing the flare bevel groove weld along the radius of HSS members.

The term "effective throat" is used when discussing fillet welds only. In the case of a groove weld, the preferred term is "weld size" or "joint penetration" in the case of single sided groove welds.

The formula you mention is consistant with AWS D1.1 where the maximum weld size for a flare bevel is 5/16 times R when the radius is assumed to be equal to 2T. Rewritten the formula is 5 times 2T divided by 16. Reduced the formula can be rewritten as: 5T/8. This is how the formula appears in AISC 13th eddition. It is interesting to note that AISC uses 3T/2 or 1.5T as the value of C, which most of us would take as being the radius. It appears to be a little like "double talk" because I don't see where the value of C is actually used for sizing welds.

The maximum weld size permitted is based on the flare bevel being filled flush. If the engineer specifies a weld size smaller than the maximum permitted by AWS, the amount of underfill would be: E(max) - E(specified), where E is the weld size measured along the minimum failure path perpendicular to the adjacent surface. Any weld that is not filled flush is somethiing less than the maximum weld size permitted by AWS or AISC.

As for measuring the radius, that is normal procedure because I have encountered many cases where the radius was something less than 2T. Radii of 1T or 1.5 T are encountered on a regular basis for wall thicknesses of 1/4 inch or less.

I would include a sketch, but my computer is being worked on as I type. I'm using a borrowed laptop. Yes, my computer was hacked, it caught a virus, whether it was the swine flu or not is open to debate. I took it to a computer wizard to save all my recent data that hadn't been backed up and he in the process or reformating my hard drive. This weekend will be spent reloading all my programs. Fun, joy, yawn!

Best regards - Al

By ssbn727 (*****)

Date 11-06-2009 21:10

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By 803056

Date 11-07-2009 20:08

Hello Henry;

Thanks for the links. I will give them a try.

I just got my computer back. The technician was able to save all my data by pulling the harddrive and downloading the files before reformating the drive. Now I have to reload all my programs, but that's a small price to pay considering the "cost" of losing my client files, etc. I do backup my files, but usually every couple of weeks when I'm on the road. That will have to change (famous last words).

Best regards - Al