G.C Wants to use different anchors 6

[JLK9]

Hi All,

The G.C. has submitted an RFI stating that the anchors I specified, F1554 Gr.55,are not readily available and would delay the project schedule. He has asked to use F1554 Gr.36 but has also submitted a mill test report showing that the Gr. 36 A.R he is proposing exceed the properties of Gr. 55. The mill report show: Yield Strength = 57.2 KSI, Tensile Strength = 75.1 KSI, Elongation Test = 45%.

I think my options are (1) go through my calcs and re-run my governing cases to see if Gr.36 KSI works (I'm pretty sure it won't) (2) Accept his mill test since it meets my original design assumption of Fy=55 KSI and Ft=75 KSI. (3) Tell him to find the correct anchor rods.

Any input is appreciated and thank you all in advance.

 

[phamENG]

Hmm...if it exceeds grade 55 I'd think it would have a dual cert. Did it come from a domestic mill? If so, they may be able to contact the mill and see if they can get a statement from the mill that it meets the Gr 55 standard. If not it may still be possible, though it may be harder to reach them.

I just looked over the ASTM...I don't see any red flags. The only issue is that the material isn't marked as a certain grade. Your Tensile strength is 0.1ksi within the range of grade 55. That gives me some pause. Properties of steel aren't perfectly uniform throughout (though they are reasonably close), and the odds of the test samples being taken from the absolute weakest specimens is unlikely. I'd not be willing to stake my license on a 100psi margin.

The contractor bid the documents with the grade 55 - he should provide certified anchors. The delay is on him for not ordering them earlier or making allowances in his schedule. If you can get the grade 36 to work, the schedule saving is worth money to him, and you and your firm deserve a piece of that for helping out.

 

[jayrod12]

And around here, north of the border, 55ksi is not special order. The GC needs a new supplier.

 

[Guest090822]

When doesn't a GC want to use a different anchor?

Getting grade 36 "to work" will likely require a larger size - make sure those are available.

I also agree with jyrod12 - 55ksi isn't special order. What's most likely going on is the guy he wants to buy from to save $0.01 per anchor doesn't have them. I've called out plenty of GCs in my career for this type of stuff. GCs are always playing games.

 

[jayrod12]

I would make a call to a local fabricator that you have a good relationship with, and ask him about the availability. And then choose the direction from there. If your fabricator friend indicates it should be no issue, then it's an easy RFI answer. If he confirms the lack of availability, then work towards a different solution.

 

[Rabbit12]

I'll echo others, grade 55 is generally not an uncommon anchor rod material. Are these by chance machine bolts? What diameters are you talking?

 

[ldeem]

I have used mill certs in the past to get a few extra ksi over the design assumption but typically the mill cert is much higher than what I need.

Why not counter with allowing Gr 36 but go to a larger size? Depending on your situation larger sizes at critical locations. The trade off of drilling out a bunch of base plates may encourage a little harder look for Gr 55 material.

If they have a mill cert I would guess they already bought the anchor rod material and have figured out they ordered the wrong grade. I say this because the mill cert would be tied to the heat of steel they were made from which would vary with the steel suppliers inventory. Since inventory is constantly turning over it seems a streach a steel supplier would hold inventory to the side an wait for the GC to decide if they want it.

 

[phamENG]

Agreed - it's quite common here, too.

You should get your hands on the spec and read through the requirements and understand the statistical derivation of the strength shown on the mill cert. If you reject it, this is what will happen:

GC: The project is going to be delayed two weeks because of the anchor bolts.
Owner: What do you mean? Why is that causing a delay?
GC: It's the engineer. I gave him information on anchors that are just as strong as the ones he specified, but he rejected them anyway.

And then there's an angry call to the architect about how your slowing down the project, and so you and your firm's reputation gets knocked down a notch or two.

Never mind that there are legitimate concerns about the compatibility of less well understood metallurgical properties of the anchors - they're strong enough and should be good enough is all the owner will understand. You need to make sure you understand the reasons to back up your decision. Something along the lines of "the test data provided by the mill may show that they are of a similar strength, but they did not meet the needed ____ standard and so could fail in ____ way without warning causing a catastrophic failure of your building."

 

[phamENG]

Ideem - in a perfect world, you're right. But I've received "preliminary mill certs" before. In other words, the contractor is sending something from a previous job to show what he plans to order. Then, after the order is placed, they send the mill cert for the actual material for record keeping purposes (and to confirm that what they bought still meets the reqs). Sometimes they're upfront about, sometimes I had to ask the question "why is this mill cert dated for 12 years ago?"

 

[BridgeSmith]

What's most likely going on is the guy he wants to buy from to save $0.01 per anchor doesn't have them.

Or that's what he has already lying around in the shop...

I say hold the GC to what was specified, or next time you, or someone else, will have to deal with the excuse "They let me do it last time!"

Rod Smith, P.E., The artist formerly known as HotRod10

 

[BridgeSmith]

The mill certs may be typical properties (or maybe not), but the specified yield and tensile strengths for each grade are minimums, with the great majority of specimens (95%, if it's the same as reinforcing steel) being stronger. There's likely to be variations, even within one heat or lot, and obviously they can't test the tensile strength of the bolts they send. So, you're likely to get some bolts that have an Ft of 80 ksi and some that are 70 ksi, whereas the real Grade 55 bolts would vary from 74.5 ksi to 85 or 90 ksi.

Someone asked why the bolts weren't dual certified; I'm fairly certain if the average Ft is 75.1 ksi, they can't assume 95% of the bolts will exceed 75 ksi as required to be certified as Grade 55.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[WARose]

What's most likely going on is the guy he wants to buy from to save $0.01 per anchor doesn't have them.

Or that's what he has already lying around in the shop...

Bingo!

 

[LittleInch]

You might need to go through your calcs to find out what will work.

If this is grade 42 e.g. or even 45 then maybe these bolts will do and be within the required amount.

But it's a slippery slope and you could get caught again later on and feel pressure to make a similar decision but with smaller margins.

how you prove that they are "not readily available" is key here.

definitely worth a few phone calls and web searches to find some somewhere on the planet to present in your defense. Cost to you is probably irrelevant, but to the GC....

If you do go down that road, I would want a lot more than one mill test and insist on additional testing of the actual bolts, say 1 in every 100 or 50 (chosen by you and tested by a 3rd party, with costs to the GC) to prove that the material actually supplied is what it says on the bit of paper your GC has. It's amazing then how suddenly a supply of the right bolts might appear.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[kipfoot]

Depending on your relationship with the owner and contractor and the precedent you want to set on the project, I may go with either option 1 or option 3. I would not consider option 2. You either have the certification or you don't.

Let the owner know in advance that you'll be billing for your time in research and redesign for the change so they're not surprised. You can also have a discussion about who absorbs the cost when the contractor wants to save money.

 

[STrctPono]

Poor planning on the Contractor's part should not be cause for you to put your neck out on the line.

I understand that in the real world, we all do it sometimes, but c'mon... Grade 55 anchor bolts are not special order. Grade 105 is a different story. Contractor's have pulled this on me in the past, and I promptly have called the suppliers, confirmed that they have them, and then call the Contractor's bluff.

 

[AaronMcD]

I used 105 for some moment frame anchors and it was no problem here in SF.

Contractor said the simpson product I speced to hold down a shallow joist is special order. Well it's either that or special steel fabrication... they had it ordered and delivered within a couple days. How long could it possibly take to order some common anchors? Are they pouring tomorrow?

http://www.hellodwell.design

 

[Wallache]

Yeah no kidding. F1554 Grade 55 has a couple of hits on Amazon, they could have it tomorrow.

 

[r13]

The linked paper is a good read. It also states the you can request supplementary tests be done to verify the grade:

S1: Weldable version of the Grade 55 specification. Through chemical composition restrictions and by a carbon equivalency formula, S1 provides assurance of weldability. When S1 is not specified, the Grade 55 material may or may not be weldable.

S2: Permanent manufacturer’s identification on the end of the anchor bolt that projects from the concrete, in lieu of color coding.

S3: Permanent grade identification on the end of the anchor bolt that projects from the concrete, in lieu of color coding.

S4: Charpy Impact requirements at +40⁰F (+5⁰C) for grades 55 and 105. The minimum Charpy V-notch energy requirement is an average of 15ft-lbs for three specimens, with no one specimen falling below 12ft-lbs. Charpy Impact requirements at -20⁰F (-29⁰C) for grade 105. The minimum Charpy V-notch energy requirement is an average of 15ft-lbs for three specimens, with no one specimen falling below 12ft-lbs.

Also, you can compare the chemical properties of the submitted certificate with those listed in the paper.

Link

 

[IceNine]

I actually specified grade 36 on a recent project and received an RFI asking if they could use grade 55 because they are more readily available.
SE USA.

 

[r13]

Yeah, the linked paper says that grade 55 can be substituted for grade 36, if the supplier chose to.