I'm a new CWI and handed out my first failure today. Brought half of the job to a stand-still and made a lot of people mad. I am inspecting welds on base clips of pre-cast panels. If you are not familiar here is a quick run-down. The bottom of the pre-cast wall has a steel embed in it that lines up with a steel embed in the footing. These are connected by a 4x4 plate welded to the footing and panel embeds. I failed it due to ark strike outside of the weld across the plate. So far I have failed three of these plates due to ark strike. There is probably 80+ of these plates on this building. Eventually these get covered by high-strength grout. These clips are at the bottom of pre-cast panels with concrete T-sections making up the roof. In other words, it is holding up a hell of a lot of weight. The superintendent is trying to get the engineer out there to overrule me. I checked the welders papers and he is certified. It will be quite an undertaking to cut the plates out and weld new ones on. In defense of the welder, (because I've been there) these clips are hard to get to. Pretty much the only way to do it is to lay down in the mud, dirt, and gravel in order to weld these and like I said there are a lot of them to do. So what does everybody think? Should I have failed them?
CYA brother! D1.1 I assume is what you're using?
D1.1:2008 5.29 "Arc strikes should be avoided... Cracks or blemishes caused by arc strikes SHALL be ground to a smoothe contour and checked to ensure soundness."
I would think another NDT method would need to be employed, maybe UT to check them out.
You got pictures?
If another NDE method is used, it would not be a volumetric one. PT or MT would be the viable option. However; most places only utilize a close visual.
bruce69,
One of my worst jobs was inspecting tilt-ups. I spent about 9 months in a prison that was under construction. After the first couple of months, when they had completed minimum security and shipped in inmates, they went to 90% inmate labor. There ended up being all kinds of problems with this.
As far as rejecting these connection plates due to arc strikes, be careful. Just as a warning. The code states that arc strikes should be avoided. There is no requirement for them to be repaired, just because they are arc strikes. What will necessitate a repair is when arc strike discontinuities are called cracks. By labeling them as such you may be required to prove your position. One of the difficulties in doing so is applying MT to an area that is not required to have MT performed, as this is the most common way to confirm a crack.
Bruce
It is my guess that the EOR will override you. From your description, the loads on these plates seem to be in compression.
Joe Kane
Fail yes, cut out no. A grinder will likely fix all that ails it.
Do these also have embed plates on the sides of each section that line up with the embeds on the adjoining panel, which gets a slug welded between them before the backer rod gets installed?
Yes, they have them they are called "vector connections."
These conditions are easily corrected by grinding. The deepest, nastiest arc strikes I have ever seen only penetrate about 1/8". Which goes to show they are still important to keep an eye out for them as they can be a crack initiator. However consider that 90% of precast connections are for lateral restraint and/or designed to be loaded in shear. The actual weight of the panels, beams, columns, T's, double T's, Triple T's, risers... is transfered via bearing pads and or grout (packed or flowable). Some connections, usually groove welded, are designed to transfer compressive or tensile loads, but that does not sound like your condition.
Additionally, MT is more than adequate to verify removal of the affected area. Unless you have a 5 to 10MHz transducer (and corresponding test procedure) you will not see an indication even if a crack has started.
Bruce- Have they started welding the slugs in yet?
By Nanjing
Date 03-24-2009 15:08
As a new CWI you may feel you are being baffled by science by the responses here but I think you did the right thing. You just need to learn, with experience, how not to make this like this a show-stopper. In my opinion all you needed to do was ask for the arc strikes to be removed by grinding and do a quick visual, and if the material is higher strength and more supsceptible to cracking, insist on magnetic particle test to ensure that no cracks have formed. Do not worry you, will get there and I think you have the right attitude to start out with as an inspector, don't be bullied. Good luck.
NKG
I am occasionally the EOR for tilt-ups which my office designs. I support the findings of the CWI on the job, unless he/she is clearly wrong or incompetent. And I support exactly what you are doing.
Tilt-ups tend to fare poorly in earthquakes because there is not a whole lot of "give" in those connections to absorb all the forced motion those connections will possibly see. Any flaw in the welds will show itself at the worst time. According to the new building codes (IBC), most of U.S. is now in some sort of earthquake country so this is likely relevant wherever you are.
Bob Garner
Looks like there are a lot of other great articles regarding welding. Can anyone provide a link to, or please send me a copy of these articles?
Welding
Alternate acceptance criteria series:
principles and use July 92
weld profile Sept 92
porosity Nov 92
arc strikes Jan 93
undercut Mar 93
weld size May 93
craters July 93
incomplete fusion Sept 93
surface slag Nov 93
weld length Jan 94
overlap Mar 94
cracks May 94
Weld convexity limits - interpretation of AWS July 92
What's the minimum size fillet weld? Mar 93
Minimum weld size - a follow-up Sept 93
New weld termination provisions Nov 93, Mar 94
Welding Inspection and OSHA Jan 95
These would be great teaching aids.
swnorris,
You can email Robert Shaw, PE at info@steelstructures.com. He may still have some of these. SSTC (the web site linked above) is his company.
His web site is at
http://www.steelstructures.com/index.html -Bert
Thanks for that arcticle third eye. I will be carrying that with me at all times when on the job.
The verdict is in: They were removed with a grinder. Thanks for everyone's input, this forum really is a wealth of information.
