Tag Archives: LRFD

Deep Foundations Research

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In the course of digging throughout the internet for data and information for a couple of projects using one of the best wifi routers, I came across some (relatively) recent research reports geared toward improving design of driven piles based on field testing.  A report from The Illinois Center for Transportation at the University of Illinois at Urbana-Champaign is focused on improving pile design through increased resistance factors and nominal bearing values.  A project by the Institute for Transportation at Iowa State University focuses on developing LRFD design procedures for steel piles in Iowa. It was published in two volumes, with Volume I covering the development of LRFD calibrations and a load test database, and Volume II covering field load tests performed for the project.

I have not had time to dig into them yet, so I just offer the links and abstracts to pique your curiosity.  Perhaps you may find something interesting in them, or maybe something applicable to a project.  There is a lot of research going on out there for TRB and NHI, so I figure sharing interesting tidbits helps get things circulated.

Click on the name of each of the research centers above to find out what other things they are doing, available reports, etc.


Improved Design for Driven Piles on a Load Test Program in Illinois, Research Report FHWA-ICT-12-011, Illinois Center for Transportation, University of Illinois at Urbana-Champaign, July 2012 (Authors: Jim Long and Andrew Anderson, )


Dynamic pile testing and one static load test was performed in accordance with ICT project R27-69, “Improved Design for Driven Piles Based on a Pile Load Test Program in Illinois.” The objectives of this project are to (1) increase the maximum nominal required bearing that designers can specify to reduce the number and/or weight of piles, (2) decrease the difference between estimated and driven pile lengths to reduce cutoffs and splice lengths by development of local bias factors for predictive methods used in design, (3) increase reliance of pile setup to increase the factored resistance available to designers, (4) reduce the risk of pile driving damage during construction, and (5) increase the resistance factor (decrease in factor of safety) based on increased data and confidence from load tests in and near Illinois. Project deliverables can be categorized as (1) better prediction methods for stresses during driving, (2) better prediction methods for pile capacities using resistance factors for driven piling based on local calibrations that consider the effects of pile setups, and (3) collections of static and dynamic load test data focused on Illinois soils and geology.



Development of LRFD Procedures for Bridge Piles in Iowa, Volume I: An Electronic Database for PIle LOad Tests (PILOT) (Volume I), Institute for Transportation at Iowa State University, January 2011 (Authors: Matthew Roling, Sri Sritharan, Muhannad T. Suleiman)


For well over 100 years, the Working Stress Design (WSD) approach has been the traditional basis for geotechnical design with regard to settlements or failure conditions. However, considerable effort has been put forth over the past couple of decades in relation to the adoption of the Load and Resistance Factor Design (LRFD) approach into geotechnical design. With the goal of producing engineered designs with consistent levels of reliability, the Federal Highway Administration (FHWA) issued a policy memorandum on June 28, 2000, requiring all new bridges initiated after October 1, 2007, to be designed according to the LRFD approach. Likewise, regionally calibrated LRFD resistance factors were permitted by the American Association of State Highway and Transportation Officials (AASHTO) to improve the economy of bridge foundation elements. Thus, projects TR-573, TR-583 and TR-584 were undertaken by a research team at Iowa State University’s Bridge Engineering Center with the goal of developing resistance factors for pile design using available pile static load test data. To accomplish this goal, the available data were first analyzed for reliability and then placed in a newly designed relational database management system termed PIle LOad Tests (PILOT), to which this first volume of the final report for project TR-573 is dedicated. PILOT is an amalgamated, electronic source of information consisting of both static and dynamic data for pile load tests conducted in the State of Iowa. The database, which includes historical data on pile load tests dating back to 1966, is intended for use in the establishment of LRFD resistance factors for design and construction control of driven pile foundations in Iowa. Although a considerable amount of geotechnical and pile load test data is available in literature as well as in various State Department of Transportation files, PILOT is one of the first regional databases to be exclusively used in the development of LRFD resistance factors for the design and construction control of driven pile foundations. Currently providing an electronically organized assimilation of geotechnical and pile load test data for 274 piles of various types (e.g., steel H-shaped, timber, pipe, Monotube, and concrete), PILOT (http://srg.cce.iastate.edu/lrfd/) is on par with such familiar national databases used in the calibration of LRFD resistance factors for pile foundations as the FHWA’s Deep Foundation Load Test Database. By narrowing geographical boundaries while maintaining a high number of pile load tests, PILOT exemplifies a model for effective regional LRFD calibration procedures.



Development of LRFD Procedures for Bridge Piles in Iowa, Field Testing of Steel H-Piles in Clay, Sand, and Mixed Soils and Data Analysis (Volume II), Institute for Transportation at Iowa State University, September 2011 (Authors: Kam Weng Ng, Muhannad T. Suleiman, Matthew Roling, Sherif S. AbdelSalam, and Sri Sritharan)


In response to the mandate on Load and Resistance Factor Design (LRFD) implementations by the Federal Highway Administration (FHWA) on all new bridge projects initiated after October 1, 2007, the Iowa Highway Research Board (IHRB) sponsored these research projects to develop regional LRFD recommendations. The LRFD development was performed using the Iowa Department of Transportation (DOT) Pile Load Test database (PILOT). To increase the data points for LRFD development, develop LRFD recommendations for dynamic methods, and validate the results of LRFD calibration, 10 full-scale field tests on the most commonly used steel H-piles (e.g., HP 10 x 42) were conducted throughout Iowa. Detailed in situ soil investigations were carried out, push-in pressure cells were installed, and laboratory soil tests were performed. Pile responses during driving, at the end of driving (EOD), and at re-strikes were monitored using the Pile Driving Analyzer (PDA), following with the CAse Pile Wave Analysis Program (CAPWAP) analysis. The hammer blow counts were recorded for Wave Equation Analysis Program (WEAP) and dynamic formulas. Static load tests (SLTs) were performed and the pile capacities were determined based on the Davisson’s criteria. The extensive experimental research studies generated important data for analytical and computational investigations. The SLT measured loaddisplacements were compared with the simulated results obtained using a model of the TZPILE program and using the modified borehole shear test method. Two analytical pile setup quantification methods, in terms of soil properties, were developed and validated. A new calibration procedure was developed to incorporate pile setup into LRFD

Calibration of Resistance Factors for Drilled Shafts -A report from the LADOTD

Note: Okay – I’ll admit – I also do a blog for the Geo-Institute Deep Foundations Committee.  as such, there are often things that I feel should be posted at both – to get the widest possible audience! So, if you have already been over there, this post will look very familiar.  It is much easier to reuse a post written by yourself. – Robert

With the adoption of LRFD design methods by the American Association of State Highway and Transportation Officials (AASHTO), the Federal Highway Administration (FHWA), and most state Departments of Transportation,  the big question in the geotechnical world is “What resistance factor should we use for __________?”.  AASHTO LRFD Bridge Design Specifications provide a lot of guidance, but many in the industry are working to calibrate resistance factors to regional or local design methods and soil conditions. Various universities and state DOTs, with assistance from FHWA, National Highway Institute (NHI), and the Transportation Research Board (TRB) are conducting research projects to provide some answers to the big question (there is never just one answer in geotechnical engineering!).

Randy Post over at GeoPrac.net recently blogged about a newly released report from The Louisiana Transportation Research Center and the Louisiana Department of Transportation and Development (LADOTD) on their investigation for calibrating resistance factors for the design of axially loaded drilled shafts.  From the report abstract:

As a continuing effort to implement the LRFD design methodology for deep foundations in Louisiana, this report will present the reliability-based analyses for the calibration of the resistance factor for LRFD design of axially loaded drilled shafts using Brown et al. method (2010 FHWA design method). Twenty-six drilled shaft tests collected from previous research (LTRC Final Report 449) and eight new drilled shaft tests were selected for statistical reliability analysis; the predictions of total, side, and tip resistance versus settlement behavior of drilled shafts were established from soil borings using both 1999 FHWA design method (O’Neill and Reese method) and 2010 FHWA design method (Brown et al. method). The measured drilled shaft axial nominal resistance was determined from either the Osterberg cell (O-cell) test or the conventional top-down static load test.

You can download a PDF of the report here.

LRFD Design Procedures Case Histories – Iowa ASCE Geotechnical Conference

Paul gave a presentation recently at the Iowa ASCE Geotechnical Conference where he discussed two project case histories for LRFD design of bridge foundations.  The meeting was held March 3, 2011 in Ames, Iowa.  In his presentation, Paul gave an overview of the LRFD design procedure as it applies to foundations, reminding them that LRFD is not difficult and that it provides a logical framework for incorporating reliability into foundation design.  Paul talked about our experiences using LRFD for foundation design for two bridges over the Mississippi River: the Hastings Bridge in Hasting Minnesota and the new I-70 bridge in St. Louis, Missouri.  Both bridges are currently under construction.

A PDF of his presentation can be found at the link through the image below, or on our Presentations page.

PJA_Iowa ASCE_3 MAR 2011

Previous Hastings posts

Previous I-70 posts