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How to handle uncomfortable technical disagreement/concern over design
3

How to handle uncomfortable technical disagreement/concern over design

How to handle uncomfortable technical disagreement/concern over design

(OP)
I have a situation in my office where I'm involved in a design and disagree with a principle that, in my mind, could have significant safety considerations. I've already aired my opinion, but others disagree, because it's just been done in other applications without problems.  I just don't buy into that philosophy, especially when there is no technical literature on the subject.

I genuinely have concerns, but I don't know what else to do given that I've  already put my concerns on the table and they've been dismissed.

RE: How to handle uncomfortable technical disagreement/concern over design

EIT v PE.  One seals the drawing, one doesn't.

I agree that "the old guys" often seem to dismiss "the young guys" as a matter of course, but virtually all of these situations can be resolved by asking the senior, "OK, so what am I missing?"

RE: How to handle uncomfortable technical disagreement/concern over design

SEIT...in looking at your posts and answers for quite some time, I have a sense that you are quite sharp.  

You need to let those who don't listen understand that because there has been no repercussion in the past does not mean that the approach is correct.  That's considered anecdotal evidence, not supporting corroboration.  Anecdotal evidence is often a "one-time"occurrence.  It does not establish precedence.

Document your objection in writing to your principals.  It only takes one of these issues to completely sink a firm...and it's usually because someone didn't pay attention to reality.

Stick to your guns...you seem to know what you're doing.

RE: How to handle uncomfortable technical disagreement/concern over design

First, are you sure you're right?  Keep discussing it with people to make sure you aren't mistaken.

As far as "it's worked all along," is this something that is particular to your company, or is this some industry-wide standard?

RE: How to handle uncomfortable technical disagreement/concern over design

SEIT...  

I have to agree with Ron here.  You can push your point, but only so far.  Without your PE, after you have voiced your opinion, you have to CYA in writing, then move on with your life.  It's their decision and their responsibility at that point.  You have done your due dilligence.

Mike McCann
MMC Engineering
Motto:  KISS
Motivation:  Don't ask

RE: How to handle uncomfortable technical disagreement/concern over design

(OP)
I've asked what I'm missing - the answer doesn't satisfy me. Stating that "we've applied this in x application with no problems" and saying it's an office decision to apply this just doesn't do anything to address my basic and fundamental concerns.

I understand that some things come down to judgment, and I also understand that I'm not signing or sealing anything and I'm just an EIT, but, again, THAT, in and of itself, does nothing to address my concern.

Using it in x application means little to me. There's no telling how "overdesigned" using their principle, or what % of the design load it's ever seen.

Thanks for the vote of confidence, Ron.  I'll try to do some more research to demonstrate the lack of literature on the topic and bring it up again.

RE: How to handle uncomfortable technical disagreement/concern over design

(OP)
Nutte-
I can't say I'm right for sure, there's no literature on the subject, but a previous.post on this forum suggests that I'm certainly not wrong. I admit there is definitely some judgment involved, but the criticality of the condition along with the forces involved and the fact that this is a global stbaility of the structure issue makes me uncomfortable.

RE: How to handle uncomfortable technical disagreement/concern over design

SEIT:
There isn't technical literature on every detail and every situation, so you can't count on that in every case.  You might explain the problem here in detail and get some outside ideas or direction.  Maybe someone outside your office has run into this issue before.  But, you do have a gut feeling that you should get resolved.  You seem smart enough to me too, so that I would give you a listen if you came to me with your concerns.  And, I would try to explain to your satisfaction, but you better come with evidence, because I know that what we have been doing has worked in the past.  We all hate to admit that we were wrong or could do it better, all at the hands of the young guy.

I agree with TXS when he says that the boss is signing the plans and has ultimate responsibility.   You usually do have trouble arguing with success, when it has worked before.  But, most good bosses will explain their thinking when asked properly, and presented with sound, logical well reasoned concern, given a little time so cooler heads prevail.  We want you to succeed, you're the best asset we've got, we secretly want you to keep us on our toes, we're not infallible.  Approach each of the 'others' individually to air and explain  your concerns.  Sometimes you get a better hearing, one-on-one, when the group thinking thing, agree with the boss mentality isn't prevailing.

I agree with Ron, but would say it a bit differently.  You must present your best case, explaining your concerns, with whatever corroborating evidence you can find.  Explain your gut feeling with the best evidence you can muster, and dissect what they are doing with your best examples and disproofs at every step along the way as to why you think their way is unsafe or wrong.  I don't think Ron meant notarized letter, by certified mail.

Good Luck
 

RE: How to handle uncomfortable technical disagreement/concern over design

dhengr...thanks.  Nope, didn't mean anything "official", just good research and statement of position.  With good references and corroborating evidence, the argument can be persuasive.

RE: How to handle uncomfortable technical disagreement/concern over design

(OP)
Ok, here's the scoop.  I appreciate all opinions.

We have some braced frame columns subject to net uplifts on the order of 2000 kips (that's not a typo).  It is being suggested to lap anchor rods with rebar in a drilled pier with no consideration of any other failure mechanism from App. D (specifically, pullout).  It is suggested that you can lap the threaded rods directly with rebar with no nut on the threaded rods (or an inadequate nut by pullout capacity) and all is good.  

I suggested that App. D is written specifically for this type of application and that we can get out of the tension breakout calcs by lapping with rebar, but we still need to comply with the pullout requirements.  

I was told that micropiles are done all the time with threaded bars with no nuts on the ends and that the rod just develops in the concrete.  

I've done a pretty exhaustive search, but can't find any literature on development lengths of threaded rods.  The thing that concerns me most is the magnitude of the loads and the fact that this type of failure could literally cause the building to topple over.  I just don't feel comfortable lapping extremely heavy threaded rods (Gr. 105) with rebar as though the transfer mechanism into the concrete is equivalent.

Any thoughts?

RE: How to handle uncomfortable technical disagreement/concern over design

I would also be skeptical of that detail.  The anchor rod has to be properly embedded into the concrete for the lapped rebar to take hold.  To me, "properly embedded" means plate washers or something of that sort, not bond between the threads and the concrete.

RE: How to handle uncomfortable technical disagreement/concern over design

The threaded bar can develop bond in the concrete. Check out Williams Form Engineering for concrete and rock anchors and basic application of the Uniform Bond Stress Model and the 45 DEG cone method. I know its "antiquated" but it worked for the US Nuclear Industry for many years. With work I have done I have assumed that the 45 DEG breakout cone starts at half of the effective embedment. You can also check out Dwyidag for similiar uses. In my dealings with Williams they have stayed away from Appendix D, stating that large scale tests have not been completed on anchors greater than 1" and that ACI has not published new material on post installed grouted anchors. Williams posts basic information from ACI 349 which is the old code for Nuclear Work, it may be enough to get you started.   A conservative value for the bond at the grout concrete interface can be taken as 300 psi. These same values have been used at the grout to rock interface. The grout or concrete steel interface will exceed this value.  Williams shows a hex nut which is typically used to insure the the failure is at the grout concrete interface and not at the steel interface. This same method can be used for the hollow core bars they show with or without mechanical anchorage. I did find two papers at work that may help you. Once again...these are not inline with Appendix D...so you may have to move outside the code to perform your analysis.

http://www.williamsform.com/Contact_Us/PDFs/High_Capacity_Concrete_Anchors.pdf

RE: How to handle uncomfortable technical disagreement/concern over design

I gained comfort using this for underwater applications. Owner would not allow any adhesive epoxy style anchors, owner would not allow mechanical anchorage (concerned that anchorage may relax over design lifespan), and we were applying large loads 100-200 kips / anchor to existing structures. Divers performed all work underwater. The comfort for me was that all anchors were pull tested. Tensions and elongations were recorded.

I am not sure how that 2000 kips is getting distributed so you may still have major concerns.

RE: How to handle uncomfortable technical disagreement/concern over design

StructuralEIT,

How bad does it fail if you check pullout?

 

RE: How to handle uncomfortable technical disagreement/concern over design

I'd review ACI 12.15.6 -splices in tension ties.  I think the drilled pier with a net uplift of 2000 kips meets the characteristics of a tension tie member as described in R12.15.6.  I wouldn't rely on a lap splice to transmit the load from the anchor rods to the drilled shaft.

RE: How to handle uncomfortable technical disagreement/concern over design

(OP)
Well, with no nut it has zero pullout capacity, so..............

RE: How to handle uncomfortable technical disagreement/concern over design

I don't believe that the situation described here is a tension tie member unless the loading is always there.  If transitory due to wind or earthquake, it is a normal connection, not a tension tie.

The threaded rod obviously has capacity, else adhesive anchors don't work.  I would look at the ratio of capacity of threaded rods to reinforcing bars using the same adhesive, then apply this ratio to the splice length required in the concrete.  Testing of this type splice would help, but I would be comfortable with this logic in the interim.

RE: How to handle uncomfortable technical disagreement/concern over design

Well, we wouldn't say that a lapped rebar (with no nut) has zero pullout capacity.  Something doesn't seem right about saying a threaded rod lapped with a rebar has no pullout capacity.

Isn't the difference here that you are providing a threaded rod?  There will be a superior bond around the rod due to the threads (similar to a deformed bar).  Aren't most typical anchor bolts that are smooth most of the length and thus need the nut at the end for pullout capacity?

RE: How to handle uncomfortable technical disagreement/concern over design

See attached for quick discussion on grout bonded anchors. It seems you are not anchoring in grout rather directly in the concrete. However, you could extrapolate that the concrete is your grout. Now analyze the bar / concrete interface. The bar has pullout capacity.

Put down Appendix D for the day and play devil's advocate.

See if some of the information provided can develop the capacities you are looking for. Call Williams...tell them you are planning to embed 2" DIA. 150 KSI All Thread Bar in concrete and see what they say. Then call DSI Dwyidag and get the European feel for what you are doing.

It might not be the perfect application or the 100% correct way of doing things in a perfect world...but lets see if it works with some basic analysis techniques. You need to build a case either for or against your argument.  

RE: How to handle uncomfortable technical disagreement/concern over design

I've always treated threaded rod the same as rebar for development, except, for heavy tensile loads I invariably use Dywidag threadbar for the anchor rods. This product is like rebar...

RE: How to handle uncomfortable technical disagreement/concern over design

SEIT, your company has used this method before ... has it been tested ?  to say it's acceptable 'cause we accepted it before is abit "off", to say it's acceptable 'cause we've proved that it works is something completely different.  maybe a scale test ??

RE: How to handle uncomfortable technical disagreement/concern over design

(OP)
No, it hasn't been tested.   

RE: How to handle uncomfortable technical disagreement/concern over design

You have a duty of care to the community. I was once pressured into a engineering design which I know doesn't conform with the building codes. It was the most unethical thing I have ever done. If you know something is incorrect you have got to argue the point until the cows come home.

RE: How to handle uncomfortable technical disagreement/concern over design

SEIT, I also respect your knowledge based on your posts on this board.  You should not simply "let it go" because you're an EIT and you're talking to PE's.  If you present your argument in a respectful way, the PE should not get angry, they should respect you for your ethics and have more confidence when you will soon become a PE yourself.

One piece of advice I would give you, is approach the PE with a SOLUTION, not just a problem.  If you can say, "hey I've done a lot of research, and we may be able to do it better using this detail", you're likely to get a lot further than throwing your hands in the air and saying "it doesn't work, and I don't know how to make it work"

RE: How to handle uncomfortable technical disagreement/concern over design

SEIT:
As others have said, stick to your guns.

But I am questioning if the detail can be slightly modified for it to work. I am assuming that you have nuts at the ends of these threaded rods. The failure mechanism is by pulling shear cone failure.

Per Appendix D, if you are able to provide U bands that are developed past the shear plane, then you are okay to transfer the tension from the anchor rod (by nut bearing) into rebar. If you remember, we had discussion on this very topic not too long ago.

Just lapping anchor rods to rebar does not sound too convincing.

RE: How to handle uncomfortable technical disagreement/concern over design

(OP)
I appreciate the input from all. I've presented a solution, but it is not desired to have a plate (or even a nut) on the threaded rods.  I honestly can't get a reason why from anyone other than, "it's been done before".

Believe me, I am by no means a "chicken little" proclaiming that the sky is falling, but I like to have a good gut reaction to details.  

slick- it is proposed to have no nuts or plates at the ends of the rods, just straight up lapping them with rebar.  

I'm trying to find out if there are any "threaded" rods that have been tested to comply with A-615.  Maybe some have been tested for this purpose, but it didn't jump out in my search on development of threaded rods.

RE: How to handle uncomfortable technical disagreement/concern over design

Dywidag threadbar... bar is cheap... but nuts are expensive...

Dik

RE: How to handle uncomfortable technical disagreement/concern over design

(OP)
threadbar only goes up to number 14, and the capacity isn't high enough.  I'll try to rework the detail to get more of them in there to get it to work.  

That 2000k is service, the factored uplift is near 3000k.

RE: How to handle uncomfortable technical disagreement/concern over design

SEIT,  there comes a time when arguing with an engineer is like tilting at windmills.

you say they've analyzed it but you're worried about a combination loadcase ... maybe their opinion is that the combination is improbable (what we'd call a double failure case ... doesn't happen)

they've used this in the past, so they'd be reluctant to test it now ... a failure now would result in considerable and expensive rework to existing structures.

is there some oversight group you can go to ?

can you Prove it bad, or do you just think it's not good ?  to prove it bad, are you assumptions too conservative ?

could you interest a nearby university into studying it as a thesis ??

good luck, and when it's your turn, you can design it properly.

RE: How to handle uncomfortable technical disagreement/concern over design

Threadbars are available in sizes much larger than #14.  Williams has up to #28 (3.5") Grade 75. and 2.5" Grade 150.  DSI also has large threadbars.

Per FHWA-RD-96-017, Drilled and Grouted Micropiles: State -of-Practice Review, Page 91, the typical ultimate design bond value for grout and a deformed steel bar is 2.0 to 3.0 MPa.  3.0 MPa = 435 PSI.

www.PeirceEngineering.com

RE: How to handle uncomfortable technical disagreement/concern over design

"It hasn't failed yet," was the attitude at NASA that essentially led to both of the Space Shuttle disasters; the complacency arises from skirting the line and surviving.  But the law of large numbers will eventually get you.

Is there any way to do a small scale test?

TTFN

FAQ731-376: Eng-Tips.com Forum Policies

RE: How to handle uncomfortable technical disagreement/concern over design

this is a very interesting thread. usually we're all about "how do i check bending on a blah blah." but a disagreement with your employer over a detail which has life-safety implications is very serious.

obviously you've brought this to attention and been "shot down" repeatedly. i would document your concerns like Ron said, but by email to multiple people in your company. keep it in house.

i agree that "it's how we've always done it" is the worst answer in the world for your question. it's moronic and uses no engineering ration. but make sure you maintain honor and respect when dealing with your employer. always maintain that respect so no one can ever say you were hot-headed or a finger pointer (i'm not implying that your are, just saying).

plead your case, give your reasons, back it up with calculations, and let them make the ultimate decision. do everthing necessary and in your power so that you can sleep at night knowing you did everything you could do.

what i'm having a hard time understanding is why are they so resistant to putting a nut on the end of the threaded bar? how expensive can nuts be in relation to the cost of a structure that has 2000 kip uplift column forces? IMO, putting nuts on the threaded bars solves the issue.

p.s. i saw an advertisement in recent SEA magazine for 97ksi #20 bar used in new WTC tower. it seems like the ceiling for threaded bar size/strength of has been raised.

RE: How to handle uncomfortable technical disagreement/concern over design

What reason does you P.E. give for not putting a nut on the threaded rod?  Is their only response that we haven't done this in the past, so it isn't necessary, or is there some other reason?   

RE: How to handle uncomfortable technical disagreement/concern over design

(OP)
I'm the only one who's done any engineering on this detail.  When I came back with the nut and plate detail I was told that we're not going to do that because they've never done it before.

I have looked at the Williams bars and they say that they meet A-615 for deformations.  

That makes me feel a lot better and I think that is the direction that we're heading after a recent conversation I initiated.

RE: How to handle uncomfortable technical disagreement/concern over design

(OP)
jt-
That and "the threads have some ability to develop the bar, so it's contribution isn't nothing" is all I was given.
I agree it isn't nothing, but there's nothing I can find that gives a rational way to quantify it.

RE: How to handle uncomfortable technical disagreement/concern over design

Lets not act like just because this is not in Appendix D we cannot validate the design. People in geotech, tunneling, and deep foundations use similiar techniques. As stated, it might not be the preferred method and I would agree it would be nice to have a nut and washer. I also agree its a good challenge to have with your colleauges. Good luck and keep it safe!

RE: How to handle uncomfortable technical disagreement/concern over design

(OP)
LSP-
I'm not saying we can't validate the design because it's no in App. D, but I wasn't being anything to make me feel comfortable about it.  The fact that it may have been done a thousand times before does not make me sleep any better at night.

It looks like the Williams bars, however, put the issue to rest.

RE: How to handle uncomfortable technical disagreement/concern over design

EIT-
How many anchors are we talking about here?
I have not read the thread thoroughly, and I didn't catch the diameter of the rods either.

My concerns with the threaded rods has always been that the load is transferred through the threads to the concrete anywhere there are threads. So, there can be load transferred to the concrete near the surface. To me, this is a poor detail.
I routinely design anchor rods/bolts with an anchor plate and a nut.  The lapping of the rods and foundation bars is to ensure that the load is properly transferred to the foundation system. I usually use smooth anchor material and only thread the portion that extends above the pier or foundation. This helps ensure that the load engagement is at the anchor plate depth, not near the surface.
AISC DG1 has a table for the pullout strength of rods with jsut single embedded nuts, but even that scares me because often the bearing area of the nut is small. If you to due a straight bearing check on the area of the nut, the bearing stresses are are very high. A small anchor plate usually is more than enough to completely eliminate this concern.
 

RE: How to handle uncomfortable technical disagreement/concern over design


BTW-for a braced frame with uplift forces in that range, you must also have some incredibly high shear forces at the column bases...just a thought.

I agree with you that there are concerns ....foundations are a hard thing to fix; if not impossible.  

RE: How to handle uncomfortable technical disagreement/concern over design

SEIT,

I've designed micropiles for both tension and compression using threaded bars without any lower nuts and plates.  


www.PeirceEngineering.com

RE: How to handle uncomfortable technical disagreement/concern over design

You do not sign the drawings; you should voice your complaint but ultimately you are not responsible for the drawings.  Take it as a lesson learned for when you sign drawings that is all you really can do.  I would not go out of my way to have my complaint in e-mail form.  You are only inviting trouble with no real benefit to you.  I have had to design things I did not like, quite a few times, I voice my complaints at the time and moved on.  If the person signing the draws wants to use old standards, fuzzy logic, or poor engineering judgment, there is nothing you can do other than letting building official or state board know.

RE: How to handle uncomfortable technical disagreement/concern over design

once again I agree with Hokie. My gut feel is development length should be about 50-60dia.  

An expert is a man who has made all the mistakes which can be made in a very narrow field

RE: How to handle uncomfortable technical disagreement/concern over design

A machine thread has no development in concrete, but a headed anchor rod (or the typical nut and plate washer should develop the full strength of the rod.  As long as the anchor rod extends far enough into concrete, and laps with the rebar extending into the pier, the anchor will be developed.  You avoid App D considerations by providing confinement in the form of ties or spirals, and by crossing the failure plane(s) with reinforcing.

The most likely tension-failure plane in the pier concrete is a horizontal cross-section near the end of the anchors, which will be restrained by the rebar crossing the plane, and developed fully above that plane.

The pier reinforcing needs to be developed above the failure plane, extending to a depth of pier sufficient to hold down the structure.  Headed or hooked reinforcing can be used to reduce development length.

Use of A615-conforming threadbar (Dywidag, SAS, etc.) as an anchor rod requires more consideration than using A1554 anchor rods.  Bars and nuts are different sizes, and special details will be required.  Mechanical splices may be preferred to laps with the high loads described, and threadbar can be connected to standard A615/A706 rebar with typical mechanical splices for rebar.

John Turner CSP PE
CRSI Greater Southwestern Regional Manager

RE: How to handle uncomfortable technical disagreement/concern over design

I was intrigued by the situation and thought of a detail for consideration.

I can't pretend to fully understand what's been said, but to resist a force one needs a static component, right?

Wouldn't welded components in concrete resist better with a perpendicular head/washer/disk than none?

I think there's also the consideration of ethics.  

Best of success, StructuralEIT

RE: How to handle uncomfortable technical disagreement/concern over design

Lovepuzzles: It sounds like you are talking about headed bars.

In accordance with ACI 318-08 12.6, headed bars can develop the reinforcing bars (or anchor rods) in tension over a short distance (l_dt), which is roughly 15 bar diameters.

A few practical considerations:
-Pier cages are sometimes placed and then cut to length, or otherwise cut to length in the field.
-Congestion may be an issue, resulting in conflict between anchor rods and pier reinforcing, particularly where anchor rods are connected as a unit before placement.  
-12.6 requires minimum spacing of headed bars.

Headed anchors are not permitted for development of bars in compression, per ACI 318-08 12.6.3. (Similar to the restriction on hooked bars.)

RE: How to handle uncomfortable technical disagreement/concern over design

Maybe in the USA thread bar dosn't develop in concrete, but in australia it is possible. we will even use smoth bar for fitment development.
 

An expert is a man who has made all the mistakes which can be made in a very narrow field

RE: How to handle uncomfortable technical disagreement/concern over design

Rowing,
Threadbar which has deformations equal to A615/A706 rebar will develop.  Machine thread "all thread" does not develop to any usable extent.

A straight, smooth bar will not develop, even at hooks.  Adhesion between portland cement concrete and smooth steel is negligible.

RE: How to handle uncomfortable technical disagreement/concern over design

Says who, TXS?  Saying that all thread does not develop usefully is a very broad statement.  And if hooks of smooth bars do not develop, there are a lot of beams all around the world with shear stirrups that are in trouble.   

RE: How to handle uncomfortable technical disagreement/concern over design

RE: How to handle uncomfortable technical disagreement/concern over design

"A straight, smooth bar will not develop, even at hooks.  Adhesion between portland cement concrete and smooth steel is negligible."

Perhaps our concrete comes with extra stickiness.

BS8110 Table 3.27 lists bond/lap lengths for plain bars (ie those with no deformations) which are generally about 80% greater than for deformed bar.

It stands to reason that all-thread bar bond lengths will lie somewhere between that for plain and deformed bars.

RE: How to handle uncomfortable technical disagreement/concern over design

Thanks greg, here is a simlar article but free.

http://wpage.unina.it/gamanfre/paper/Experimental%20Response%20and%20Behavioural%20Modelling%20of%20anchored%20smooth%20bars%20in%20existing%20rc%20frames.pdf

TXS,
I can see that in high seismic regions that smooth bar should be considered like a deformation anchor. That is to say: the development length should be such that little to no deflection along the bar anchorage should occur before plastic behaviour of the structure.  While this requirement may limit the use, it shouldn't negate the use.  

An expert is a man who has made all the mistakes which can be made in a very narrow field

RE: How to handle uncomfortable technical disagreement/concern over design

TXStructural said, "A straight, smooth bar will not develop, even at hooks."  However, per FHWA Publication No. FHWA-SA-97-070, Micropile Design and Construction Guidelines, Implementation Manual, June 2000, Sec. 5.E.5 Grout to Steel Bond Capacity, Page 5-30; the typical ultimate bond values range from 1.0 to 1.75 MPa (145 to 254 psi) for smooth bars and pipe and 2.0 to 3.5 MPa (290 to 508 psi) for deformed bars (ACI 318).  This bond for deformed bars is a litle different than the value I quoted above from a different FHWA Manual.

www.PeirceEngineering.com

RE: How to handle uncomfortable technical disagreement/concern over design

If smooth reinforcement has no reliable bond development, I wonder how pretensioning works.  I know, the wires are twisted, but they are still smooth.

Interesting to me that people depend on modern glue for developing threaded rods, but don't like to depend on portland cement glue.  

RE: How to handle uncomfortable technical disagreement/concern over design

That is a good question hokie, maybe it is because it has rusted a little 2thumbsup so the awnser to the riddle maybe that we need to rust the smooth/threaded bars a little and the bond will be good.    

An expert is a man who has made all the mistakes which can be made in a very narrow field

RE: How to handle uncomfortable technical disagreement/concern over design

Hokie... smooth wires, unless they are greased have some bond... albeit a smaller value.  With P/T stuff, there is a slight Poisson effect that tends to make the ends a little fatter...

Dik

RE: How to handle uncomfortable technical disagreement/concern over design

I was speaking from a code perspective.  ACI 318 does not recognize development of smooth, mild reinforcement.  As for strand, it does have to be very clean to bond.  It also has a greater surface area per unit length, and the twist of the strand increases the bond.  The FHWA pub mentioned does not recognize smooth bar in the discussion of types of reinforcing.

I am certainly not saying that there is zero surface bond between steel reinforcing and portland cement paste.  Deformed bar develops primarily because of mechanical interlocking of the deformations, paste and aggregate, and surface bond with cement plays a significantly lesser role.  Surface bond is susceptible to factors which do not adversely affect development of deformed bars or wire to the same extent.

As for ASTM F1554 all-thread, there will be some development, but again, it is not comparable to A615/A706 deformed bar.

RE: How to handle uncomfortable technical disagreement/concern over design

TXS,
Thanks for clarifying your earlier posts.  I think we all agree that deformed bars are the way to go in most cases.

RE: How to handle uncomfortable technical disagreement/concern over design

(OP)
I really didn't just let it go, so I kept looking and I found that the threads on Williams bars meet ASTM A615 for bar deformations, so this is the bar we'll be using.  This is helping me sleep much better.

Thanks to all for the input and discussion.

RE: How to handle uncomfortable technical disagreement/concern over design

All of the GR60, GR75, and GR150 threadbars from DSI, Williams, Skyline, and SAS Stressteel meet A615.  These are the bars commomly used for tieback anchors, tiedown anchors, and soil nails.

www.PeirceEngineering.com

RE: How to handle uncomfortable technical disagreement/concern over design

Smooth bars develop at about half the rate of deformed bars. If it takes X to fully anchor a deform bar, a smooth bar will take about double that (that comes from my old 1920s concrete book). So surface bond is quite significant.

Also, mechanical interlock ramps up after surface bond slip occurs, so in reality many deformed bars are working via surface bond anyway...

That's not to say you should use use smooth bars!, but just to point out that bond isn't "zero" for smooth bars.


Back in the olden days all bars were smooth....

RE: How to handle uncomfortable technical disagreement/concern over design

Tomfh,
It is incorrect to say that all bars were smooth in the old days.  What can be said is that there was a wide variety of types of reinforcement, including smooth bars, twisted bars, and a lot of different types of deformed bars.  Not until about 1947 did the US standardise on the deformations, and that time period varied in other countries.  

RE: How to handle uncomfortable technical disagreement/concern over design

ok, point taken. change "all" to "a lot of"

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