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]

retired - that's a dangerous thing to allow without consideration. Seismic connection requirements mandate certain ductility requirements, and that usually means tensile yielding of the anchor bolt has to control the design (no sudden, catastrophic concrete pullout failures, etc.). By giving blanket authorization to increase the yield stress of the anchor, you could inadvertently mess up the intended ultimate load behavior.

 

[canwesteng]

Grade 36 is also often weldable and grade 55 is not, another reason not to just swap them willy nilly.

 

[r13]

Great points, gentlemen.

 

[STrctPono]

Grade 36 is also often weldable and grade 55 is not

Mostly true. My ASTM says "Weldable Grade 55 may be furnished when Grade 36 is ordered." This correlates correctly with retired13's link. Never noticed this before. Agree with phamENG, I don't like this.

 

[r13]

Good find, STrctPono. The supplier has the option (of his own) to substitute one grade for another, but it can be done only through the submittal of "deviation request" along with mill tests and certificate for the substitute materials. The engineer still holds the ultimate power to accept or reject the intend substitution.

 

[msquared48]

If the contractor wants to use different anchors, without certified test data of the order provided by Simpson or similar manufacturers (Hilti, etc), I would make the contractor supply the test certs, what load combinations those certs applied to, what grade of concrete, cracked or uncracked, etc.

No certs, no approval.

Mike McCann, PE, SE (WA, HI)

 

[JStephen]

On some miscellaneous stuff like this, what we run into is that Product A is available quickly from a reliable local supplier, and Product B requires us to deal with somebody we've never dealt with before halfway across the country and hope they can make their promised delivery. It's not the $0.01 extra that's the issue, but having to wait an extra week to get the "odd" item.
That said, we've only used Grade 55 weldable once or twice, but I don't recall them being any problem for us to get, either.

 

[phamENG]

JStephen - thanks for bringing a different perspective into this.

I understand what you're saying - dealing with known entities is always preferable. What are your thoughts on the contractor's responsibility to identify those potential schedule issues ahead of time and account for them in the schedule? And if they fail to do so, what are your thoughts on the contractor compensating the engineer (directly or indirectly through owner back charges) for the time spent making a design change to keep the contractor's schedule on track?

 

[JStephen]

phamENG, I understand the "contractor compensating the engineer" issue, but it's not one we normally run into either. It usually amounts to either or-equal substitutions in the shop-drawing phase, or redesign work for me (contractor employee).

 

[Whoopdedo_LSU]

You’re steel is failing? Your design should be concrete failure in my eyes. Optimize the design.

 

[TLHS]

I don't understand why this is a question that I always get as well. My solution is now to tell contractors that if they can't find it, call Hilti and buy it from them. Their HAS-E-55 is ASTM F1554 Gr 55 and their HAS-V-36 is F1554 GR 36. They have some standard lengths in stock and they will custom cut you any length up to several feel long with a couple days notice. I know in the Canadian manual there's a chart that has the standard lengths available and the turn around for custom sizes.

You're probably paying a bit of a premium, but I know you can get it from them without me searching.

 

[JLK9]

Thank you all for the excellent feedback, especially since this isn't the last time I'll have this discussion with a G.C.

In anti-climactic fashion, the G.C miraculously found a large supply of GR.55 after I spent several hours going through my calcs.

 

[LittleInch]

the G.C miraculously found a large supply of GR.55

Perhaps the GC was reading this post.....

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

 

[skeletron]

@JLK9: I've had a similar experience with screw anchors. Original spec was regarded as "too big of a lead time, gotta import them from California." What followed was a month of weekly questions about "would this work instead?" or "we found a box of these, are they adequate?" After finally finding an alternate that was acceptable, they tried to install them and they just wouldn't go in. Now the project is behind a month, there's no more options, and they tried to force my hand to use the original alternate they wanted to use. I called up the manufacturer who verified that, yes indeed, they have thousands in their warehouse about thirty minutes from the job site. It was a big lesson for me to always do my own research...