Smith
Road Bridge #03.730.
Just another bridge on the BCEO's roster of 369 bridges. Yet,
this seemingly small, insignificant bridge near the City of Hamilton
/ Ross & St. Clair Township lines has become the focus of
national media attention. The Butler County Engineer's Office
has installed a structure built entirely of advanced composite
materials originally designed for use in the aerospace industry
-- fibers such as glass embedded in epoxy.
The bridge, rechristened
the Tech
21 Bridge, was
dedicated on July 25, 1997 and
is the first of its kind in Ohio and only the third in the nation.
Ohio Governor George V. Voinovich
and Ohio Senator Mike DeWine
each issued proclamations heralding the event as a positive contribution
to Ohio's rich transportation history and as good for the economy.
"This structure exemplifies the success of public/private
partnerships in Ohio and indicates the state's continuous ability
to create a positive business climate for the high-technology
industry," Voinovich stated.
Local Background
The use of composite
materials for civil infrastructure applications has been ongoing
and locally, the Butler County Engineer's Office has an established
history of testing progressive technologies such as this. Our
recent ongoing work with Wright Patterson Air Force Base, Martin
Marietta Materials, and LJB Engineers & Architects, Inc.,
on the bridge composites is yet another chapter being written
and added to this rich tradition.
Fear Not Mills Road
Bridge #00.260 over Mutton Run in St. Clair Township was the
first bridge to be tested. It has become the field laboratory
for a new and innovative repair technique utilizing composites.
Paper-thin Carbon-Fiber Reinforced Polymer (CFRP) laminate materials
were applied by BCEO crews to the underside of two beams in September
1995. This technique is commonly referred to as "plate bonding."
A year later, one of
the beams was removed from the bridge and transported to Wright
Patterson in Dayton (Ohio). There, it was subjected to a load
test to determine how the material held up under normal field
conditions, including the winter freeze-thaw cycle and road salt.
The result: the beam withstood more than 20 percent greater weight
than a standard beam and had retained 94 percent of its initial
strength increase from the composite application. The other beam
will be removed after four years and subjected to the same test.
Future applications
could prolong the lives of aging bridges, increasing safety and
saving taxpayers repair and replacement costs.
Tech 21
Bridge
Down the road, we see whole bridges
built of the composites, like the new Tech 21 Bridge on Smith Road. Structural
Polymer Matrix Composites (PMC) such as glass fibers in thermosetting
resins were used in the construction of the Bridge, providing
high specific strength, specific stiffness, and corrosion resistance.
It is also lightweight, corrosion resistant, and stronger than
steel. This could provide a long-term alternative to concrete
and steel in future bridge construction.
The Tech 21 Bridge is also the nation's first
fully instrumented bridge. Health monitoring instrumentation
provides performance evaluation under actual field conditions.
This smart bridge has special sensors embedded within
that are linked to a system of computers at the BCEO for continuous
monitoring. This will provide valuable data on environmental
and other life-cycle effects which cannot be simulated under
short term testing. (Initial tests indicated the load capacity
of the Bridge well exceeds AASHTO specifications by considerably
more than a factor of 2.0.)
The Tech 21 Bridge
project is in fact a research and design project that, if proven
economically feasible, could result in a permanent transfer of
this technology into the general market. What is learned from
this and other similar composite studies will be factored into
future projects.
Additional
Composite Tests
Another test that will
be conducted includes placement of three-eighths inch thick carbon
tendons in one of the beams on the Fear Not Mills Road bridge.
The tendons will be laid in epoxy-filled parallel grooves. After
a few years, the beam will be removed and subjected to a stress
test.
During the summer of
1998, a concrete conspan bridge was installed on Yankee Road
in Liberty Township. The bridge utilizes composite fiber reinforcements
in one section and in the wingwalls.
The BCEO is not only
a leader in the laboratory and the design of composites, but
also in the field application process as well. Our crew members
were instrumental in developing the field application of the
rehabs with Wright Patterson.
Plans are in the works
to continue the plate bonding and tendon rehabilitation techniques.
We may also utilize a few more bridges built entirely of the
composites.
