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Federal Highway Administration > Publications > Public Roads > Vol. 69 · No. 3 > National Highway Institute

Nov/Dec 2005
Vol. 69 · No. 3

Publication Number: FHWA-HRT-05-001

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The National Highway Institute (NHI)

901 N. Stuart Street, Suite 300

Arlington, VA 22203

www.nhi.fhwa.dot.gov

New NHI Course Bridges Gaps In Bridge Specifications

With the goal of ensuring a more uniform level of safety and reliability for highway structures, the Federal Highway Administration (FHWA) and the American Association of State Highway and Transportation Officials (AASHTO) established an October 2007 deadline for States to transition to using load and resistance factor design (LRFD) specifications for highway bridges.

LRFD incorporates state-of-the-art analysis and design methodologies with load and resistance factors based on the known variability of applied loads and material properties. The load and resistance factors are calibrated from actual bridge statistics to ensure a uniform level of safety. Because LRFD specifications are probability-based and incorporate working stress design and load factor design (LFD), while accounting for extreme events like ship collisions with bridges and earthquake damage, they can help produce more reliable structures.

To help States obtain the practical hands-on technical training necessary to transition to the LRFD platform, the FHWA Office of Bridge Technology and the National Highway Institute (NHI) are introducing a new course, LRFD for Highway Bridge Substructures and Earth Retaining Structures (#130082A).

To date, some States have adopted the new LRFD specifications to varying degrees, while others are designing bridges in relatively close accordance with traditional specifications.

A new NHI course on LRFD specifications will help engineers produce more reliable designs for bridges like these three over the Ohio River near Louisville, KY.
A new NHI course on LRFD specifications will help engineers produce more reliable designs for bridges like these three over the Ohio River near Louisville, KY.

Traditionally, States either followed the allowable stress or LFD platform, and AASHTO maintained two sets of national specifications: Standard Specifications for Highway Bridges, 17th Edition, and Load and Resistance Factor Bridge Design Specifications, 3rd Edition. NHI's course strives to unify the Nation's design approach by presenting the most up-to-date guidance, including a proposed specification rewrite for structural foundations. Because of LRFD's applicability across disciplines, this comprehensive set of specifications also can help improve communication between structural and geotechnical specialists.

The new course replaces the former NHI course, LRFD for Highway Bridge Substructures (#13068), and covers current national practices and procedures for structural design, along with geotechnical design and foundation engineering. To improve delivery of the content, instructors emphasize hands-on exercises and sample problems.

Upon completing the course, participants will be able to do the following:

  • Define LRFD limit states and compute structural and geotechnical design loads
  • Integrate the LRFD specifications into their local practices
  • Apply LRFD criteria for design
  • Integrate the geotechnical aspects of LRFD foundation design into LRFD structural design

The LRFD course targets a variety of infrastructure specialists, including mid-level bridge and geotechnical journeymen and mid-level design engineers. The course also can accommodate entry-level designers with LRFD experience and experienced designers who have worked with allowable stress design or LFD but not LRFD.

"The transition to LRFD is simply a language translation," says Jerry A. DiMaggio, principal bridge engineer at FHWA. The new course will help dispel concerns that the transition to LRFD could be complex, difficult, and costly, or result in designs that are too conservative or not conservative enough.

Each course installment is delivered by two experienced instructors--a structural engineer and a geotechnical specialist--in an onsite classroom format using a comprehensive participant's manual and a reference manual as teaching tools. The course is available in four formats, with timeframes ranging from 1 to 5 days.

For more information on this course, contact Jerry A. DiMaggio at 202-366-1569 or jerry.dimaggio@fhwa.dot.gov. To schedule a course, contact the NHI Training Coordinator at 703-235-0500 or nhitraining@fhwa.dot.gov. To obtain information about NHI courses, access the course catalog at www.nhi.fhwa.dot.gov or contact NHI at 4600 N. Fairfax Drive, Suite 800, Arlington, VA, 22203; 703-235-0500 (phone); or 703-235-0593 (fax).

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