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).
