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June 2017 - DFI Helical (Screw) Pile Seismic Research Study Update - Phase I Literature Review has Been Completed
by Bill Bonekemper
This author was honored to have witnessed days of extremely detailed preparation by Dr. Cerato and her team of grad students, a tremendous effort by the contracting crew, awesome shake table testing and massive amounts of data recording at the DFI Helical (Screw) Pile Seismic Study shake table testing event last month near San Diego. It was a proud, proud moment in history for the helical pile industry when the shake table engineer announced “. . . 3-2-1- running,” and the giant sandbox, as it was affectionately called, began to move to and fro in short sudden bursts for periods lasting around thirty seconds or so. With as many as forty people in attendance on test days, and with everything from studio quality TV cameras to cell phone videos focused on the weights attached to the top of each of the (10) helical test piles, everyone was absolutely mesmerized during each test phase.
There will be pages and pages written about this event and the all-important test results over the months and years to come. The intent of this article is to inform our industry about how well this project was planned and executed through the efforts of our funding companies, Dr. Cerato, her team of graduate students, companies and organizations that donated products and fixtures, and by the incredible commitment made by the Torcsill contracting team.
- The total amount of cash contribution pledges to date - $134,000
- Companies contributing cash – Atlas Tube, CTL/Thompson, Deep Foundations Institute, EXEL Tube, Foundation Supportworks, Foundation Technologies, GoliathTech, Helical Pile Association, Helical Pile World, Hubbell-Chance, IDEAL Group, Lally Pipe, MacLean Power Systems, Magnum Piering, Patriot Foundation Systems, Ram Jack, Techno Metal Post, Torcsill
- Companies that contributed helical piles, caps, weights and specialty structures – Ram Jack, Torcsill, Magnum Piering
- Helical pile contractor that contributed material trucking, installation equipment and a (3) man crew for the duration - a $75,000 in-kind contribution - Torcsill
- National Science Foundation (NSF) - RAPID Award - click here to learn more about NSF RAPID
- Number of human hours to instrument helical piles - 240
- Number of days from mobilization to test completion and demobilization – 24 days
Number & Description of Test Piles
- Total of ten test piles – (1) 3.5” hollow square tube; (5) 3.5” round shaft; (4) 5.5” round shaft
- Number of strain gauges and accelerometers that had to be affixed and cabled – (152) strain gauges and (10) accelerometers
Description of Weights Attached to Tops of Piles
- First Weight Test (free-head) - 850 lb. (average) concrete donut weights; (2) weights on four of the 3.5” piles; (1) weight on two of the 3.5” piles; (3) weights on two of the 5.5” piles, and (2) weights on the other two 5.5” piles
- Second Weight Test (pinned and fixed) – (1) steel container loaded with 8,000 lbs. of sand attached to four 3.5” piles; (1) steel container loaded with 16,000 lbs. attached to the four 5.5” piles
Shake table tests
- Number of shake test days - 5
- Number of shake tests conducted – 29
- Names of simulated shakes and magnitudes – Kobe (Japan), 1995, 7.3 magnitude - Northridge (CA), 1994, 6.7 magnitude
- Shake sequences - 50% Northridge, 75% Northridge, 100% Northridge, Time Compressed 100% Northridge; 50% Takatori, 75% Takatori, 100% Takatori
DFI - HPTC Member
The Movers & Shakers Team
Recently Dr. Amy Cerato submitted the final draft of the (91) page paper titled “A Critical Review: State of Knowledge in Seismic Behavior of Helical Piles” to the Deep Foundations Institute (DFI) for publication. The paper is the deliverable that successfully completes Phase I of the DFI Helical (Screw) Pile Seismic Research Study that was initiated in the Spring of 2015. The document will be available soon as a downloadable DFI Journal Paper.
Dr. Cerato and her team are now focused on completing Phase II of the study, which entails the review, compilation and summarization of the enormous amount of data that was collected during the shake table testing at the UC San Diego facility in February 2016. HPW will report the progress on Phase II as more information and deliverables become available.
Below is a reprint of an article HPW published soon after the February 2016 shake table testing was completed.