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- To: seaint(--nospam--at)seaint.org
- Subject: API Pipes as Pile Matl
- From: Abolhassan Astaneh-Asl <astaneh(--nospam--at)ce.berkeley.edu>
- Date: Sat, 16 Aug 2008 10:13:08 -0700
Dear Mr. Zabala:Couple of years ago, we did a number of steel pile tests (all H-piles) and developed design guidelines which are in the current AISC Seismic provisions (2005). One of the most important issues was local buckling. Although we did not do tests of pipe piles, but based on what we learned from these tests, i would give me my 2-cents on your question, hoping that others with more direct experience will jump in and contribute and specially correct me!
Here is my 2-cents:If the pipes are with welded seams, it has to be shown that the seams will hold up under the impact during the pile-driving process. If the pipes are seamless, then you can take a look at the URL below which has comparisons of chemical composition and mechanical properties of seamless pipes made of ASTM A53 Grade B and API-5L grades 42 to 60.
http://www.geocities.com/ferroslav/fcemmec.html (please be warned that this site has elevator music in the background!)It seems that the API-5L Grades 46 and higher strength grades have ultimate elongation that varies from less than 17.5% to 28%. The lower end is a bit of concern in being less than 20%. If there are reliable material properties on these pipes such as mill certificates or better yet actual ASTM coupon tests, then one can compare their mechanical properties to other steel used in steel piles. You may want to ask Pile Driving Contractors Association (http://www.piledrivers.org/askpdca.php ) about their experience and how they feel about driving these piles. I have had very good experience with this group in the past. Their motto is "Driven piles are tested piles!" You may want to have 2-3 of these piles actually driven at the site and even have a lab do a pile loading test on them if you end up finding no precedence in other people using them successfully.
For seismic regions, even for non-seismic areas, if the pipe piles are filled with concrete, they will perform really well specially if seismic loads are large. Filling the piles for at least 10-20 feet from the top can make a big difference in their performance.For local buckling issues your piles having D=12" and t=.50" makes a D/t of 24 is far less than 0.11E/Fy for applications where seismic R factor is 3 or less and even less than more stringent seismic limit of 0.044E/Fy for D/t ratio of pipes in applications with R> 3.0. My understanding is that local buckling under impact compression can occur easier than when the member is subjected to gradual application of compression load but I am not aware of any local buckling limits for compression applied under impact (high strain rate) as is the case with driven piles.
Finally, you also need to look into corrosion behavior of these piles, but, that is beyond my qualifications to comment on. Best wishes. Abolhassan Astaneh-Asl, Ph.D., P.E., Professorand Consultant on Structural Engineering, Earthquake Engineering and Protection of Buildings and Bridges against Blast and Impact
(www.ce.berkeley.edu/~astaneh) From: milo zabala <milozabala(--nospam--at)yahoo.com> Subject: API Pipes as Pile Matl To: seaint(--nospam--at)seaint.org --0-1922731843-1218856206=:55605 Content-Type: text/plain; charset=us-ascii List, Our client has extra API pipes (12" dia. x 1/2 thk) that he prefer to use as pile foundation for a pipe rack project. Building code does not list API pipes as pile material. Any advise on the suitability or acceptability of these material for building applications.Thanks in advance.
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