Design Analysis of Single-span Advanced Composite Deck-and-stringer Bridge Systems

There is a concern with worldwide deterioration of highway bridges, particularly reinforced concrete. Due to the corrosive nature of steel re-bars used in concrete bridge decks, the service-life of these bridges is reduced. The advantages of advanced composite materials (ACM) over conventional materials motivate their use in highway bridges for rehabilitation and replacement of structures. However, the complexity of the composites has prevented widespread implementation of ACM members in highway bridge design. There is a need for simplified design analysis procedures that account for both the geometry and material properties of ACM members and system. In this study, a combined analytical and experimental study of fiber-reinforced plastic (FRP) composite bridges consisting of cellular box decks and wide-flange I-beam as stringer is presented. The study includes design, modeling and experimental/numerical verification of FRP composite decks and deck-and-stringer bridge systems. The design analysis covers: (1) ply stiffnesses and strengths; (2) laminate engineering stiffnesses; (3) apparent stiffness iii properties for composite decks; and (4) stringer stiffness properties. A finite element modeling (NISA) is used to verify the accuracy of the design analysis. For design analysis of FRP deck-and-stringer bridge system, an approximate series solution for orthotropic plate including first-order shear deformation is developed. The results of the explicit solution are correlated with finite element analyses. Based on the analytical/experimental study, simplified design equations are developed for bridge applications, which include global design of deck-and-stringer system accounting for load distribution factors. Under this research effort, two FRP decks are fabricated. The first deck is 5'x5'x5 " and consists of bonded box beams that are 5' x 5' x 3/8 ". The second deck is 10′ × 10′ × 8″ and consists of bonded box beams that are 4 " x 8 " x 1/4 " ; the deck is further placed over FRP wide-flange I-beams (12 " x 12 " x 1/2 ") and tested as a deck-and-stringer bridge system. The box beams for decks and I-beams for stringers were both produced by pultrusion. The decks and bridge systems are tested under static loads for various boundary conditions. The experimental results are used to compare with the approximate series solution and finite element model. The comprehensive experimental/analytical results of this study are used to propose efficient FRP sections and simplified design equations for new and replacement ACM highway bridge decks and deck-and-stringer system. iv ACKNOWLEDGMENTS First I wish to thank God for allowing me …