Development of fiber reinforced polymeric deck and cable system for cable-stayed bridges
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This research study addresses the effective use of fiber reinforced polymeric (FRP) materials in cable-stayed bridges with a primary focus on incorporating the light FRP materials in the deck and the cable system. As the main span length of cable-stayed bridges increases, several technical challenges become more dominant with traditional material. Such technical challenges include: large axial stress in the main girders, cable sag effect, and flutter instability, consequently limiting chances of extending the span length of future cable-stayed bridges with traditional materials. In order to remedy these issues, this study proposes FRP composites for the deck and cable system of cable-stayed bridges in combination with traditional materials. This study seeks to answer the fundamental question: "How can FRP be used most effectively and most efficiently in the deck and cable system for cable-stayed bridges?" To use FRP most effectively in terms of static, dynamic and flutter performance, genetic algorithm (GA)-based optimizations were performed to optimize the distribution of FRP and concrete in the hybrid deck system and carbon fiber reinforced polymer (CFRP) volume ratio of each cable to maximize both static and flutter performances. To use FRP most efficiently, another GA optimization module was also developed to distribute the minimum amount of FRP in the deck and cable system to satisfy required performance limits. Implementing this GA optimization module in the traditional bridge design framework, a GA optimization-based bridge design framework was developed. To facilitate the optimization process, two numerical computer programs were developed: the analysis engine to evaluate the geometrical nonlinear static, modal, and flutter performances of cable-stayed bridges; and the optimization engine to conduct the search for optimal solutions. The analysis and optimization engines were combined into a single unit to perform the GA-based optimization process of cable-stayed bridges to make effective use of FRP materials and traditional materials that can extend the span length of cable-stayed bridges.