Origin of Drilled Post Foundation Equations in IBC 5

[JohnDeereSurfer]

I’m trying to locate the original development of the equations in the IBC that sizes post footings for lateral loads. I’ve found them in the 2018 IBC, 2001 CBC, and as far back as 1970 UBC. In the 2018 IBC they are in sections 1807.3.2.1 (Eqn.18-1)& 1807.3.2.2 (Eqn. 18-2). I believe their development may possibly date as far back as the 1940’s but I’m not sure. Can anyone refer me to the original source of their development?

 

[JAE]

Not sure exactly on the IBC equations -
Attached here is a portion of the article in the Gaylord and Gaylord Structural Engineering Handbook that references guidance on laterally loaded piles.
There is reference to an author named "Prackash" from 1961 as well as an "M. T. Davisson" - "Lateral Load Capacity of Piles, Highway Res. Board Highway Res. Rec 333, pp 104-112, 1970.

 

[HTURKAK]

That is strange .. I have 2018 IBS Illustrated handbook and section 1807.3 Embedded posts and poles, explains the development of the formulas. I have copy and pasted the relevant section;

Moreover , i have an old book ( FOUNDATIONS OF STRUCTURES BY Clarence DUNHAM, 1950 ) which has the mentioned nomogram .Pls look attached doc.




Use it up, wear it out;
Make it do, or do without.

NEW ENGLAND MAXIM

 

[JohnDeereSurfer]

JAE,
Thank you for the references and Gaylord’s pages. I will review them as my investigation advances.

HUTURKAK,
At first glance, your excerpt from the 2018 IBC Illustrated Handbook looks like exactly what I’m looking for. I wasn’t aware of this publication. I’m struggling with the definition of (d) for the nonconstrained case:

“d=Depth of embedment in earth in feet(m) but not over 12 feet(3658mm) for purposes of computing lateral pressure.”

In my hunt I’ve found people are interpreting this in at least three different ways (for computing S1):
d/3<=12, d<=12, actual hole depth <=12 ft.
and various other ways they handle it. At this point, I quit looking for the “right” interpretation. Instead I’m looking for the original development in hopes of finding what the author intended.

Check back occasionally, I intend to post the results of my search.
JDSurfer

 

[HTURKAK]

JohnDeereSurfer ,

If i understand correctly , you have problem with the definition of (d) for the nonconstrained case. ( English is not my first language so, if my interpretation does not answer to your question , we may work an examle ).

- the (Equation 18-1) is closed form equation which could be solved mit iteration or with charts ( pls look attached doc. at my first post ), and could be solved with the following steps ;

- without knowing ( d ) an initial assumption is necessary . since the equation is valid for max . d= 12 ft, assume d=12 ft ,
- calculate the S1 = Allowable lateral soil-bearing pressure as set forth in Section 1806.2 based on a depth of one third
the depth of embedment . Look TABLE 1806.2, e.g . Assume material class 4.( Sand, silty sand, clayey sand,silty gravel and clayey gravel ) TABLE 1806.2, S1 will be 4*150=600 (psf).
- calculate the required (d) for this value , and find say 9.0 ft,
- repeat the second step till d= d previous calculated , ( 2-3 iteration would be sufficient )
- or use alignment chart

I hope this respond answers your problem.





Use it up, wear it out;
Make it do, or do without.

NEW ENGLAND MAXIM

 

[JohnDeereSurfer]

HTURKAK,
Thank you for your example.
I understand the equations are closed form. Their solution is not the problem. I can easily apply any of the three interpretations I have encountered for the caveat in the definition of (d) for the nonconstrained case (S1). I just do not know which interpretation is correct. At this point, the only way to get to the bottom of this is to start with the original derivation. From my other research, I approximated its origin to be in the 1940’s. Your previous post confirmed that(thank you very much!). From it, the calculations were started in 1938 and completed in 1947 at Purdue University. At that point they were adopted by the OAAA. Then in 1964 they were adopted by the Uniform Building Code. Since then, they have been adopted by the IBC, CBC, and others. I find it alarming, everyone uses them, and seems to have their own interpretation of the caveat in the definition of (d). I don’t have a problem with the equations. During their 80 years of use, they have developed a reputation of being conservative. Perhaps that stems from the various interpretations I have discovered. I will continue my investigation. To that end, if anyone has any inside information that helps this effort, I would like to see it.
Thank you,
JDSurfer

 

[flight7]

JDS,
The interpretation of the limit on d has always seemed self-explanatory, so I'm surprised that you found so many different ways of interpreting it. Thank you for doing the community a service by digging into the original research. Please come back with your results!

 

[JohnDeereSurfer]

Flight7,
If I can find the original work, I will definitely post my findings here. Be advised though, tracking down 80 year old analyses is not easy. My search may or may not be fruitful. Stay tuned on perhaps a long term basis.

 

[JohnDeereSurfer]

To those forum members that are still following this thread, this is an update.

Since my last post I’ve been pursuing the two documents referenced by HTURKAK (dated: 10 Dec 23). I believe I located them and I can get copies of them. I haven’t done so yet because of copyright concerns. Without copyright approval from the primary controlling party, I cannot publish them here. Without publishing them, my opinion is nothing more than a fourth interpretation. I’m currently attempting to locate the original authors which I’m doubtful will happen because these documents are 70-80 years old. Locating their heirs is equally doubtful but a reasonable attempt must be made to show due diligence. If all that fails, my non-profit, educational use, presentation here may qualify as “fair use” circumventing copyright approval.

If you’re still interested, check back here occasionally for updates. Whether I succeed or fail in this pursuit, I plan on presenting my final findings here on the forum

Stay tuned.

 

[CarlB]

Thanks for the update. I did some research as well, may add on to what you find.

Regarding the question of d/3-

A maximum of d=12 feet is a limit just for determining the lateral soil pressure, S1.
That is, for cases where d is greater than 12 feet, use d=12' for determining S1. Which mean the lateral pressure is that for d/3, or 4 feet.
It is really quite clear, although Hturkak didn't pick up on it, I'll attribute that to his unfamiliarity with its use.
This interpretation is built into programs such as EnerCalc.

And flight7 says the limit on d was "self explanatory", but didn't say how he/she interpreted it, didn't disagree with Hturkak, so I wonder...

 

[HTURKAK]

Not sure how you did decide that i am unfamiliar with its use . But you are right at one point i am unfamiliar with the programs such as EnerCalc.
I would like to remind you that , i used that formula at early 70's (slide rule and simple calculator era ).



He is like a man building a house, who dug deep and laid the foundation on the rock. And when the flood arose, the stream beat vehemently against that house, and could not shake it, for it was founded on the rock..

Luke 6:48

 

[Celt83]

d = Depth of embedment in earth in feet (m) but not over 12 feet (3658 mm) for purpose of computing lateral pressure.

Actual embedment D can exceed 12ft but the lateral pressure is limited on the extreme end to the value when D=12ft.

 

[Celt83]

Beyond 12 ft the IBC equation does not account for the non-rigid pier behavior and also IBC provides no means of determining the shear and moment in the pier so you should really switch to a more detailed calculation like that done by Lpile.

 

[SlideRuleEra]

I believe I located them and I can get copies of them.
I haven’t done so yet because of copyright concerns.
Without copyright approval from the primary controlling party, I cannot publish them here.
...these documents are 70-80 years old.

Assuming the documents were published in the USA and copyrighted before 1964, chances are very good you can post them here, or anywhere else. Copyright had to be renewed 28 years after original copyright. If not renewed, the documents are in the public domain... no permission is needed from anyone. Only a tiny percentage of documents from that era had their copyrights renewed.

Read about it this FAQ I posted and check your documents. For the 17 years I had a website, had excellent reasons to get a good layman’s knowledge of USA copyright law:

When Does a Printed Document Enter the Public Domain?