- Environmental Influence on the Bond Between a Polymer Concrete Overlay and an Aluminum SubstrateMokarem, David W.; Huiying Zhang; Weyers, Richard E.; Dillard, David A.; Dillard, John G.; Jose Gomez (Virginia Center for Transportation Innovation and Research, 2000-04-01)Chloride-ion-induced corrosion of reinforcing steel in concrete bridge decks has become a major problem in the United States. Latex-modified concrete, low-slump dense concrete, and hot-mix asphalt membrane overlays are some of the most used rehabilitation methods. Epoxy-coated reinforcing steel was developed and promoted as a long-term corrosion protection method by the Federal Highway Administration. However, recent evidence has suggested that epoxy-coated reinforcing steel will not provide adequate long-term corrosion protection. The Reynolds Metals Company developed an aluminum bridge deck system as a proposed alternative to conventional reinforced steel bridge deck systems. The deck consists of a polymer concrete overlay and an aluminum substrate. The purpose of this investigation was to evaluate the bond durability between the overlay and the aluminum substrate after specimens were conditioned in various temperature and humidity conditions. The different environmental conditionings all had a significant effect on the bond durability. Specimens conditioned at 30C, 45 C, and 60C at 98 percent relative humidity all showed a decrease in interfacial bond strength after conditioning. There was also a decrease in the interfacial bond strength for the specimens conditioned in freezing and thawing cycles and specimens conditioned in a salt water soak. The only exposure condition that increased the bond strength was drying the specimens continuously in an oven at 60C.
- Implementation and Non-Destructive Evaluation of Composite Structural Shapes in the Tom's Creek BridgeHayes, Michael David; Haramis, John Emmanuel II; Lesko, John J.; Cousins, Thomas E.; Duke, John C. Jr.; Weyers, Richard E. (Virginia Center for Transportation Innovation and Research, 2000-05-01)A bridge rehabilitation utilizing a hybrid fiber reinforced polymeric composite has been completed in Blacksburg, Virginia. This project involved replacing the superstructure in the Tom's Creek Bridge, a rural short-span traffic bridge with a timber deck and corroded steel girders, with a glue-laminated timber deck on composite girders. In order to verify the bridge design and to address construction issues prior to the rehabilitation, a full-scale mock-up of the bridge was built and tested in the laboratory. This set-up utilized the actual composite beams, glue-laminated timber deck panels, and geometry to be implemented in the rehabilitation. After the rehabilitation was completed, the bridge was field tested under a known truckload. Both tests examined service load deflections, girder strains, load distribution, the degree of composite action, inter-panel deck deflections, and impact factor. The field test results indicate a service load deflection of L/400 under moving loads and a factor of safety of over 7 using the projected A-allowable for beam flexural strength. The data from the field test serves as a baseline reference for future field durability assessments as part of a long-term performance and durability study.
- Evaluation of the in-service performance of the Tom's Creek Bridge fiber-reinforced polymer superstructureNeely, W. D.; Cousins, Thomas E.; Phifer, S. P.; Senne, J. L.; Case, Scott W.; Lesko, John J. (Virginia Center for Transportation Innovation and Research, 2003-09-01)The Tom's Creek Bridge is a small-scale demonstration project involving the use of fiber-reinforced polymer (FRP) composite girders as the main load carrying members. It is a simply supported, short-span bridge located along Tom's Creek Road in Blacksburg, Virginia. As a result of discussions among Virginia Tech, Strongwell, the Virginia Department of Transportation, and the Town of Blacksburg, the existing deteriorated superstructure of the Tom's Creek Bridge was replaced with a glue-laminated timber deck on 8 in (20.3 cm) deep pultruded fiber-reinforced polymer beams. The project was intended to address two issues. First, by calculating bridge design parameters such as the dynamic load allowance, transverse wheel load distribution and deflections under service loading, the Tom's Creek Bridge will aid in modifying current AASHTO bridge design standards for use with FRP composite materials. Second, by evaluating the FRP girders after being exposed to controlled laboratory and service conditions, the project will begin to answer questions about the long-term performance of these advanced composite material beams when used in bridge design. A dynamic load allowance, IM, of 0.90 is recommended for the Tom's Creek Bridge. This value is the largest average IM observed and is therefore conservative. This value is significantly higher than those set forth in the AASHTO standards of 0.33 (AASHTO, 1998) and 0.30 (AASHTO, 1996). It is recommended to use a value of L/425 (LRFD Specification) or L/500 (Standard Specification). This value is consistent with AASHTO deflection control criteria for an all timber bridge. It is recommended to use the AASHTO wheel load distribution factors for a glulam timber deck on steel stringer bridge. There is no indication of loss of FRP girder ultimate strength after 15 months of service. Given the low service loads (no more than 10% of the ultimate capacity) and traffic volume the fatigue life prediction model suggests that fatigue will not be a major concern during the life of service (10 to 15 years).
- Health monitoring of post-tension tendons in bridgesDuke, John C. Jr. (Virginia Center for Transportation Innovation and Research, 2003-02-01)Post-tensioned concrete has been used in a number of bridge structures and is expected to be used more in future construction in Virginia. This type of detail offers unique advantages for improving the performance of concrete members. Recent problems in the United Kingdom and Florida have increased concern over the condition of post-tensioned tendons in Virginia's bridges. There is a need for efficient, cost-effective methods of assessing and monitoring the condition of aging tendons in-situ. This study was carried out to survey the literature that addresses the condition of tendons to identify technology, perform a limited assessment of the feasibility of as many of the candidate technologies as possible, and consider follow-on efforts for development and application to post-tensioned tendons in Virginia in was described.