Publication Number: FHWA-RD-02-008
Date: March 2002

FHWA Evaluates LRFD Software

In 1994, the American Association of State Highway and Transportation Officials (AASHTO) introduced a new set of standard bridge design specifications that incorporated the load and resistance factor design (LRFD) philosophy. This philosophy features the use of limit states, multiple load and resistance factors, and a more probabilistic determination of the structure's reliability. Along with the new LRFD specifications has come the need for compatible bridge design software. Recently, the Federal Highway Administration's Federal Lands Bridge office began to evaluate new software that is compatible with the LRFD specifications.

The Federal Lands Bridge office has evaluated SAP2000 and Conspan LA so far and will evaluate RC Pier, Florida Pier, CT Bridge, and Merlin Dash in the near future. SAP2000 is a three-dimensional finite element analysis tool that can be used for a range of structures, while Conspan LA is primarily used to design prestressed and precast members. Florida Pier, which was developed by the University of Florida, can be used for the design and analysis of bridge substructures and foundations. RC Pier can be employed to design substructures by utilizing strut and tie models; Merlin Dash, developed by the University of Maryland, is intended for steel bridge design. CT Bridge, developed by the California Department of Transportation, is to be used for modeling and designing post-tensioned box girders.

The evaluation criteria includes:

• Does the software follow AASHTO LRFD code?
• What are the limitations of the software?
• Is the product user friendly?
• What future development plans exist for the software?
• What type of user or product support is available from the developer?
• What is the format of and how flexible are outputs?
• What will be the cost of future program upgrades and/or the correction of any software defects?

To date, the office has used SAP2000 and Conspan LA with varying degrees of complexity on several projects throughout the United States. Once the evaluations are complete, a team consisting of bridge designers from Federal Lands' offices in Denver, Colorado, and Sterling, Virginia, will make final recommendations to the Bridge Office Leadership Team as to which software programs should be adopted by Federal Lands.

For more information on the software evaluations, contact Hratch Pakhchanian at the Eastern Federal Lands office, 703-404-6246 (email: hratch.pakhchanian@fhwa.dot.gov).

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