Tag Archives: Statnamic

NCHRP Report 461–Static and Dynamic Lateral Loading of Pile Groups

nchrp_rpt_461-Static and Dynamic Loading of Pile Groups

Here is a blast from the past on pile groups: NCHRP Report 461 – Static and Dynamic Lateral Loading of Pile Groups.  I had a request for this report recently, so I found it and figured we needed to post the links to it.  Dan was the lead researcher on this report during his time at Auburn University, and had an all-star line up that included Dr. Mike O’Neill and Dr. Mike McVay, two of the heavy hitters in foundation engineering.  The report introduction gives a good summary of the contents:

A key concern of bridge engineers is the design and performance of pile group foundations under lateral loading events,
such as ship or ice impacts and earthquakes. This report documents a research program in which the following were developed:
(1) a numerical model to simulate static and dynamic lateral loading of pile groups, including structural and soil hysteresis and energy dissipation through radiation; (2) an analytical soil model for nonlinear unit soil response against piles (i.e., p-y curves) for dynamic loading and simple factors (i.e., p-multipliers) to permit their use in modeling groups of piles; (3) experimental data obtained through static and dynamic testing of large-scale pile groups in various soil profiles; and (4) preliminary recommendations for expressions for p-y curves, damping factors, and p-multipliers for analysis of laterally loaded pile groups for design purposes. The report also describes experimental equipment for performing site-specific, static, and dynamic lateral load tests on pile groups.

Several full-scale field tests were conducted on pile groups of 6 to 12 piles, both bored and driven, in relatively soft cohesive and cohesionless soils. All of the groups were loaded laterally statically to relatively large deflections, and groups of instrumented pipe piles were also loaded dynamically to large deflections, equivalent to deflections that might be suffered in major ship impact and seismic events. Dynamic loading was provided by a series of impulses of increasing magnitude using a horizontally mounted Statnamic device.

For a relatively short (50 pages) report, there is a lot of information packed into it gleaned from a lot of full-scale field work.

DBA Wraps Up Load Test Program and Proceeds with Design on St. Croix Bridge

Project rendering courtesy of HDR 

Lateral Statnamic test, picture by David Graham of DBA, click here for a YouTube video

DBA has been selected by MnDOT as a geotechnical and load testing consultant for the design phase load test program and foundation design of a new bridge crossing the the St. Croix River near Oak Park Heights and Stillwater, Minnesota. The new bridge will carry State Highway 36 across the St. Croix River between Minnesota and Wisconsin. Currently, Highway 36 is carried on an 80-year old two-lane vertical lift bridge in downtown Stillwater.  The new bridge will divert the heavy through traffic away from the historic downtown center and reduce travel time for commuters.  The iconic lift bridge will be converted to a pedestrian and bicycle only structure.

Work began this summer on the load test program which consisted of one 8-foot test shaft, two 24-inch driven steel pipe piles, and two 42-inch driven steel pipe piles, all installed in the St. Croix River along the alignment of the new bridge.  Local contractor Carl Bolander & Sons Co. was selected as the general contractor for the load testing program.  Bolander self-performed the installation of the test piles and sub-contracted the construction of the test shaft to Case Foundation Company, of Chicago, Illinois.  Axial load testing of the test shaft was performed by Loadtest, Inc., of Gainesville, Florida, using Osterberg Cells (O-cells).  Dynamic testing of the driven piles using the pile driving analyzer (PDA) was performed by local geotechnical consultant Braun Intertec.  Axial testing of the driven piles and lateral testing of the shaft and one of each size pile was performed using the Statnamic Device by Applied Foundation Testing, Inc. (AFT), of Jacksonville, Florida.  DBA provided pre-test recommendations, assisted MnDOT in construction oversight, provided analysis and review of the test results, and made design recommendations based on the test results.

Following the successful load test program, DBA is working with MnDOT’s structural design consultants for the project, HDR, Inc. and Buckland & Taylor Ltd.  to optimize the bridge design.  Already, the design team has been able to lengthen the bridge spans and eliminate a river pier as a result of the load test results, as was recently reported by Minnesota Public Radio (MPR).  Also, because the total number of drilled shafts required to support the main pier towers has been reduced, construction on the foundations will been moved up to 2013 rather than the original estimated start date in 2014, also reported by MPR.

For more information, please see:

The MnDOT Project Page

The DBA Project Summary Sheet

Early Statnamic Lateral Load Test Paper by Dan

While at the 2012 Geo-Congress I purchased a couple of books at the ASCE bookstore.  One was GSP 88: Analysis, Design, Construction and Testing of Deep Foundations, Proceedings of the OTRC ‘99 Conference. There are several interesting papers in the GSP, including an early paper by Dan on lateral Statnamic testing.  A full scale lateral load test was performed on a 36 inch tests shaft using a Statnamic device.  The test was performed at the Auburn University National Geotechnical Experiment Station Site (NGES).  I guess you could say this paper is literally a “blast” from the past!

 

Brown, D.A. (1999). “An Experiment with Statnamic Lateral Loading of a Drilled Shaft”, Geotechnical Special Publication No. 88: Analysis, Design, Construction and Testing of Deep Foundations, Proceedings of the OTRC ‘99 Conference, Austin, Texas, April 29-30, 1999, ASCE, pp309-318.