Safety, Security, Reliability, and Efficiency: Working Together for Better Bridges and Tunnels
By M. Myint Lwin
Improving transportation for a strong America. That’s the vision
of the Federal Highway Administration (FHWA). In support of this vision,
FHWA’s Office of Bridge Technology is dedicated to working together
with our many partners within FHWA and in State, local, and tribal governments;
industry; academia; and others to provide the Nation with safe, secure,
reliable, and efficient highway bridges and tunnels. With about 600,000
bridges and 600 tunnels across the country, it is vitally important
for us to protect, maintain, and preserve these structures.
FHWA’s Office of Bridge Technology has a diversified, motivated,
and responsive staff to provide leadership, stewardship, and technical
support in successfully delivering the Federal-aid bridge program. Key
components of the bridge program include the National Bridge Inspection
Program, which encompasses the National Bridge Inspection Standards
(NBIS) and the National Bridge Inventory (NBI). The NBIS cover the minimum
requirements for inspection programs, including such things as frequency
of inspection and minimum qualifications for bridge inspection personnel.
The NBI is a compilation of data supplied by States, as required by
the NBIS, for bridges located on public roads. FHWA also encourages
and promotes the use of a systematic process, such as a Bridge Management
System (BMS), in determining cost-effective preventive maintenance activities
to extend the service life of existing bridges.
Highway Bridge Replacement and Rehabilitation Program (HBRRP) funds
are used to improve the conditions of the Nation’s existing bridges,
including preventive maintenance to extend the useful life of bridges.
Discretionary Bridge Program funds are made available to supplement
the HBRRP allocations for the rehabilitation and replacement of high-cost
highway bridges, and for the seismic retrofit of highway bridges. The
National Historic Covered Bridge Preservation Program, meanwhile, provides
funding to assist highway agencies in their efforts to preserve, rehabilitate,
or restore historic covered bridges listed in the National Register
of Historic Places.
Another key component of FHWA’s bridge program is the Innovative
Bridge Research and Construction (IBRC) Program. IBRC funds are made
available to State and local highway agencies for use of innovative
materials and techniques in bridge construction and for research into
better bridges. IBRC funds may be used for bridge repair, rehabilitation,
and replacement, or for new bridge construction. They may also be used
to support research and technology transfer activities.
Technology deployment is another crucial aspect of our office’s
work. Through publications, workshops, online communities of practice,
virtual teams, Web sites, one-on-one consultation, and other means,
FHWA is working to aid States in implementing new technologies that
can improve their bridges today and tomorrow. These technologies include
the use of self-consolidating concrete (SCC), which does not require
vibration to achieve full compaction (see article, page 4). The concrete
provides better quality, improved durability, and high strength.
The use of high-performance concrete (HPC) for bridges, meanwhile,
has become a standard practice for many States. Bridges built with HPC
are expected to last significantly longer than conventional bridges
in highway environments, which means less disruptive preservation and
maintenance work will be required. The next generation of HPC, known
as ultra high-performance concrete (UHPC), is in the final phase of
research and development. It offers ultra high strength, toughness,
and durability. The implementation of high-performance steel (HPS) is
also on the rise, with nearly 40 States now using HPS in over 200 projects.
The steel is easier to weld and fabricate, tougher, more corrosion resistant,
and has high strength.
Another technology now in use is fiber-reinforced polymer (FRP) composites.
FRP has unique properties, such as corrosion resistance, high strength,
light weight, and fatigue resistance, which make it very attractive
for the strengthening, hardening, repair, and seismic retrofit of bridges
and structures. Because FRP behaves quite differently than the conventional
structural materials, such as concrete and steel, new American Association
of State Highway and Transportation Officials (AASHTO) design codes
have to be developed and adopted for FRP to gain wider acceptance by
bridge owners.
Also showing promise is ultrasonic impact treatment (UIT) of welds.
UIT helps prevent fatigue cracking in welds and welded members of existing
and new bridges and structures (see July
2003 Focus). Eliminating the fatigue cracking increases
the service life and reduces the overall lifetime maintenance cost.
In the area of bridge design, FHWA is working with the States to fully
implement the AASHTO Load and Resistance Factor Design (LRFD) system.
LRFD is based on technological advances in bridge engineering, sound
scientific principles, and a systematic design approach to ensure safety,
durability, economy, and constructibility.
In the areas of hydraulics and geotechnical engineering, meanwhile,
FHWA is working with the National Highway Institute (NHI) to develop
manuals, guidelines, and training courses on such topics as hydrology,
hydraulic design, stream stability, scour mitigation, and driven pile
foundations.
Strong earthquakes, such as the Loma Prieta Earthquake in 1989 and
the Turkey Earthquake in 1999, have taken many lives and caused billions
of dollars in damages. The structural engineering community is intensifying
efforts to minimize the loss of lives, property, and commerce due to
structural failures in future earthquakes. FHWA and the National Cooperative
Highway Research Program jointly funded the development of a new seismic
design criteria entitled, “Recommended LRFD Guidelines for the
Seismic Design of Highway Bridges,” for adoption by AASHTO. And
under the sponsorship of FHWA, the Multidisciplinary Center for Earthquake
Engineering Research is completing a new manual to provide highway agencies
with the state-of-the-practice in seismic vulnerability evaluation and
retrofit of bridges.
Recognizing the real and growing threats of terrorism against our bridges
and tunnels, FHWA, in cooperation with the U.S. Army Corps of Engineers,
is sponsoring and conducting workshops on Bridge and Tunnel Security
Vulnerability for Federal and State personnel. Among other measures,
FHWA has formed an Engineering Assessment Team for Bridge Security and
Vulnerability to provide technical advice and field review on methods
to prevent, mitigate, respond to, and recover from extreme events. The
team will also provide training and technical support to infrastructure
owners for risk assessments.
Within FHWA, the Office of Bridge Technology is working closely with
the Office of Research and Development, the Federal Lands Highway Office,
the Resource Center, and the Division Offices to deliver quality services
and information to our customers. We have also formed a Bridge Leadership
Council (BLC). The BLC, which includes representatives from throughout
FHWA, is focused on better linking the agency’s resources to streamline
the development, testing, and deployment of new technologies and to
provide technical assistance to State and other highway agencies.
The success of our many initiatives to advance the safety, security,
reliability, and efficiency of the Nation’s bridges and tunnels
and ensure mobility depends upon strong partnerships. Working cooperatively
with our many stakeholders, partners, and customers, we can strengthen
and improve the bridges and tunnels of today and tomorrow.
As Director of the FHWA Office of Bridge Technology, I personally invite
readers to send your ideas and suggestions for continuous improvement
in bridge programs and technologies to me or to your local FHWA Division
Office. I value your ideas and suggestions and will consider them as
we refine our plans and programs. I also invite you to join the FHWA
Bridge Team in achieving the high-quality bridges and tunnels so important
to our mobile Nation’s transportation network and ultimately to
its everyday safety and security. For more information on bridge programs
and new bridge technologies, please call me at 202-366-4589 (email:
myint.lwin@fhwa.dot.gov)
or contact any of our team leaders and partners listed below.
M. Myint Lwin is the Director of FHWA’s Office of Bridge
Technology.
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