One
size does not fit all. By adding the word “not”, this now completely
revised adage rings true for at least one civil engineer.
“The
devil is in the details,” said William Wright, a scholar who was once
named the Engineer of the Year by the Federal Highway Administration.
The agency cited him for his work on ” high performance steel that led
to reduced initial cost, lower maintenance, and longer life for many new
bridges nationwide,” according to the highway administration’s press
release announcing his award.
Wright,
an associate professor of civil and environmental engineering at
Virginia Tech, is concerned about size, especially when it relates to
how materials will perform in structures where failures might lead to
catastrophes. As today’s engineers investigate the rebuilding of much of
the nation’s infrastructure, a lot of which was constructed in the
1950s, they are using much improved materials and analysis tools.
“These advances can be combined to greatly reduce the risk of failure of steel bridges by brittle fracture,” Wright said.
Based
on his expertise in engineering and materials for bridge spans, the
Virginia Tech civil engineer predicts his new work on a fracture control
plan for steel bridges “promises to change bridge fabrication and
inspection practices.”
Currently
the highway administration requires more intensive inspection for
structures that are at risk from fracture failure, a major cost factor
for bridge maintenance budgets. The current fracture control plan was
developed in the 1960s and has not kept up with advances in materials
and computerized system analysis.
Wright
is in the initial stages of this new study, funded by the
Transportation Research Board, to identify critical members in steel
bridges that need to be protected from failure by fracture. Working with
him is Robert J. Conner of Purdue University’s Civil Engineering
Department. Together, they received a $350,000 grant to develop an
improved method to determine the structural consequence if brittle
fracture occurs.
“Most
bridge engineers now have the capability of performing a particular
evaluation – a three-dimensional elastic finite element system of
analysis of bridges. This is a powerful tool that provides a platform
for studying internal load re-distribution in damaged structures such as
bridges. However, the problem remains that the ultimate strength of a
structural system made of steel and concrete is a highly non-linear
problem,” Wright said. There is limited information available about the
ultimate strength of bridge systems.
Wright
refers to the problems as “non-linear” because they can involve
combinations of steel yielding, steel buckling, concrete crushing, and
connection failure. The elastic three-dimensional method of analysis
“can greatly over estimate strength and reliability of a damaged bridge
if all factors are not considered,” Wright explained.
So,
Wright and Conner are working to create a more comprehensive approach.
They want to develop an all-inclusive systems method that would reliably
predict the fatigue and fracture limit states of steel, the ultimate
strength of the connections in the structure, the stability of the
system, the overall condition, and the value of having an in-service
inspection.
They
believe a significant cost savings could be achieved through their
approach. If states will pay a modestly higher, up front cost for better
materials, the financial burden of lifetime inspections can be reduced,
Wright said.
“The
bridges we build today present a much lower risk of fracture compared
to those built prior to about 1980. The reasons are the higher quality
standards for fracture critical member fabrication, greatly improved
knowledge about fatigue design and detailing to prevent in-plane fatigue
as well as distortion cracking issues, and improved material quality.
However, there is little evidence that fatigue critical in-service
inspection contributes significantly to this improvement,” Wright said.
Due
to these advancements in engineering, new bridges should have less need
for inspection for fatigue issues when compared to the older vintage
bridges.
As
Wright investigates this fracture critical analysis system for the
Transportation Research Board, he is simultaneously working on a
multi-state pooled fund project administered by the Indiana Department
of Transportation to develop improved fracture toughness specifications
for structural steels used in critical members. His goal is to design
and fabricate standards to eliminate fracture critical concerns in low
redundancy structures, such as two-girder bridge systems.
Working
with a host of partners including the Commonwealth of Virginia, the
Army Corps of Engineers and the Federal Highway Administration, Wright
suggests the results of this study “will be transformative for the steel
bridge industry. For the first time, material selection, design, and
inspection will be rationally integrated to eliminate fracture concerns.
This can result in significant cost savings for medium and long-span
bridges and facilitate the introduction of modular concepts for
short-span bridges.”
The
highway administration has the authority to allow the owners of bridges
to forego fracture fatigue critical inspection for low-redundancy
bridge structures on a case by case basis. However, this reprieve rarely
occurs since there is little guidance to insure bridge safety, Wright
said.
“This
project will establish guidance that provides a high level of bridge
safety that can then form the basis for in-service inspection
decisions,” Wright said.
Wright
received his bachelor’s degree in civil engineering from the University
of Maryland at College Park in 1986, his master’s degree in structural
engineering, also from University of Maryland in 1988, and his Ph.D. in
civil engineering from Lehigh University in 2003.
Throughout
his career, Wright’s primary research interests have involved
development and experimental evaluation of new, innovative bridge
systems that can meet three critical requirements: rapid construction,
life cycle durability, and cost effectiveness. He has targeted this
“Bridge of the Future” goal as the overriding principal guiding the
Federal Highway Administration research program. The current research on
fracture critical bridge systems is an enabling technology for the
“Bridge of the Future”.
Among
his honors, Wright received the 2008 Richard S. Fountain Award from the
American Iron and Steel Institute and the AASHTO T-14 Steel Bridge
Committee for his outstanding contributions to the steel bridge
industry. In 2007, he received a U.S. Department of Transportation Gold
Medal for his work on the Minnesota I-35W Bridge Response Team. In 2006,
Wright earned the George S. Richardson Medal, presented by the
Engineers Society of Western Pennsylvania and Roads and Bridges magazine
for his development of the Load and Resistance Factor Design Unified
Steel Design Code.
In
1997 the Civil Engineering Research Foundation of ASCE presented him
with its Charles Pankow Award for Innovation for his work on the
development of high performance steels for highway bridge applications.
