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A Composite Bridge
Ohio's 1st All-Composite Bridge

Tech 21
Materials Technology
for the 21st Century
(This page last updated on 3/12/01)
   Tech 21 Bridge

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.

Tech 21 Bridge Facts


    • Tech 21 Bridge -- Ohio's first all-composite bridge and the nation's first fully-instrumented bridge.


    • Smith Road Bridge #03.370, City of Hamilton, Butler County, Ohio, 2/10 mile west of State Route 128.



    • The Tech 21 Team - A unique public, private, and military team transferring technologies to bring Ohio its first composite bridge. Tech 21 is the culmination of technology transfer efforts among civil engineering and composite experts from the Butler County Engineer's Office (BCEO), Martin Marietta Materials, LJB Engineers & Architects, Inc., and Wright Laboratory's Materials Directorate at Wright Patterson Air Force Base.
Butler County Engineer's Office (Hamilton, OH) - Local engineering, bridge installation, bridge user/owner.
Martin Marietta Materials (Raleigh, NC) - Manufacturer of bridge, composite design, constructed deck and U-shaped beam.
Contact: Dan Richards, Manager-Composites
Address: PO Box 30013, Raleigh, NC 27622-0013
Phone: 919-783-4679
LJB Engineers & Architects, Inc. (Dayton/Cincinnati, Ohio) - Design and engineering.
Contact: Mark Henderson, Structural Engineer, Principal
Wright Patterson Air Force Base (Dayton, Ohio) - Wright Laboratory's Materials Directorate, pioneered research of advanced aerospace materials, testing facilities, composite project coordinator.
Contact: John Mistretta, Materials Engineer
Address: WL/MLBC Bldg 654, WPAFB, OH 45433-7750
Phone: 937-255-9059
Bridge Diagnostics (Boulder, Colorado) - Load testing and long-term monitoring.
Address: 5398 Manhattan Circle, Suite 100, Boulder, CO 80303-4239
Phone: 303-494-3230
Foster-Miller (Waltham, Massachusetts) - Environmental sensors and hardware for interfacing into the long-term monitoring system.
Address: 303 Bear Hill Road, Waltham, MA 02154-1196
Phone: 617-622-5505


    • To promote and demonstrate the use of high-tech fiber-reinforced composites for common structural applications in the construction industry for the general public's benefit and safety.

Tech 21 Bridge Design and Features

    • Low cost construction
    • Prefabricated sections
    • Modular for easier transportation
    • Light weight
    • Rapid assembly
    • Corrosion resistant
    • Redundant load paths
    • High load capacity
    • Stronger than steel
    • Fiberglass/polymer construction
    • Life expectancy over 100 years

Fibers Used

    • E-glass continuous fiber

Matrix or Resin Used

    • Polyester matrix

Tech 21 Bridge Statistics

    • Length = 33 feet
    • Width = 24 feet
    • Depth = 2 feet, 9 inches
    • Weight = <22,000 pounds
    • Deck is sandwich construction consisting of pultruded tubes between two face sheets. Tubes run parallel with the traffic direction.
    • Deck is supported by three U-shaped structural beams.

Tech 21 Bridge Photo Gallery

Click to see photos of Tech 21 Bridge delivery and unloading at the Butler County Engineer's Office, and of the July 8, 1997 installation at the Smith Road site. For more info and additional photos, please see the BCEO's 1997-98 Annual Report: Tech 21 Excerpt.

Time Line For Tech 21 Bridge Installation

      • June 9, 1997 - Close Smith Road. Begin dismantling old bridge.
      • Week of June 16 - Work on existing abutments, form concrete caps, etc.
      • June 24, 1997 - New bridge delivered to BCEO.
      • Week of June 30 - New bridge transported to Smith Road site.
      • Week of July 7 - Begin installation of new bridge.
      • July 8, 1997 - Bridge placed on concrete abutments.
      • Week of July 21 - Pave new bridge.
      • July 25, 1997 - Bridge dedication. Open bridge to traffic.

Some Composite Links


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