فناوری کنونی کامپوزیتهای FRP در پلهای بزرگراه
Abstract
1- Introduction
2- Research significance
3- State-of-current-practice survey
4- Summary and conclusions
References
Abstract
This case study presents the use of fiber reinforced polymer (FRP) composites in highway infrastructure. The state of current practice of FRP materials is established through a survey questionnaire and follow-up interviews with 46 responding transportation jurisdictions in North America (44 United States Departments of Transportation and 2 Canadian agencies) to identify current challenges requiring technical and administrative efforts to facilitate the employment of this promising construction material. FRP composites for infrastructure projects are generally satisfactory and promising. Most agencies have used FRP since 1996, although some agencies reveal pioneering endeavors in the early 1990s. The nature of construction projects determines whether FRP applications are experimental or a standard practice. The survey shows that CFRP-strengthening for upgrading bridge piers (primarily columns) is the most accepted standard practice, followed by GFRP-reinforced bridge decks. Challenges experienced by the responding agencies are detailed and analyzed. Various tests at material and structure levels are conducted to examine the performance of structural members constructed with FRP composites. Despite these endeavors, the long-term durability of in-situ FRP still requires additional research to generate technical data and to convince end-users. Lessons learned from sites are elaborated to assist practitioners who are interested in FRP-based projects. The majority of respondents state that more training is necessary to help understand the use of FRP composites in construction projects.
Introduction
The sustainability of highway infrastructure is one of the most crucial research/practice needs in the United States. Constructed facilities deteriorate owing to physical and environmental factors, and may become structurally deficient. There are a number of contributors to such deterioration; for example, water, ultraviolet radiations, temperature, freeze-thaw, traffic load, impact, and chemicals. Accordingly, structural members do not meet their expected design life. The loadbearing capacity of these members may decrease as their physical properties change, leading to public safety concerns. The members’ durability performance is also affected by the degree of deterioration (e.g., steel reinforcing bars become vulnerable to corrosion, when concrete surrounding the bars cracks or spalls). Transportation agencies are eager for alternative construction materials, which will enable them to extend the longevity of existing structural members in an economical manner. Fiber reinforced polymer (FRP) composites are a promising material and have shown excellent performance with numerous advantages. Examples involve favorable strength-to-weight ratio, noncorrosiveness, reasonable labor, rapid execution, and reduced long-term maintenance costs [2,3]. The application range of FRP materials is broad from internal reinforcing to external strengthening [7,10,9,4]. Various FRP materials and types (e.g., sheets, laminates, structural shapes, bars, and tendons) are available for highway infrastructure [1]. Further details on the various aspects of FRP applications (e.g., durability, statistical characteristics, test methods, and long-term performance) are expounded in state-of-the-art papers [8,5,6]. Although significant advancements have been made over the last two decades from research standpoints, FRP composites have not been widely adopted by state departments of transportation (DOT), including the Ministry of Transportation in Canadian Provinces, because of their high material costs, a lack of design guidelines or specifications, procurement, and relatively short application history. The FRP community is not properly informed of the contents related to the following questions: how the developed technologies are actually employed and how decision-making authorities consider such technologies in their projects. Given that the ultimate goal of all research activities is to provide end-use sectors with necessary information, answers to these questions are as important as technical investigations. This case study discusses the state of the practice of FRP composites for highway infrastructure. So informed, both transportation agencies and researchers will be aware of barriers that impede the use of FRPs and will identify directions toward future research and planning.