Development of hybrid fiber reinforcements of enhancing structures with integrated performances

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In this study, first, a comprehensive design concept of hybrid fiber reinforced polymers (FRP) composites with several types of fibers with different specific properties is proposed in order to realize different required performances including tensile strength, stiffness, ductility, creep and fatigue resistances and cost performance as one of the most important indices. Then the material behavior including the long-term performances such as creep and fatigue is experimentally investigated. Quantitative indices to evaluate and control stress or load drops during the gradual fractures of different fibers are proposed and their effectiveness are experimentally verified. The usefulness of adopting continuous fibers with higher energy absorption capacity is also verified.For the application of hybrid fiber sheets in strengthening RC concrete structures, it is found that the use of high modulus carbon fibers in hybrid systems could increase the serviceability such as yielding load. Moreover, … More it is conformed that structures can be strengthened with appropriately designed hybrid fiber reinforcements of consisting of three type of continuous fibers with different specific properties to meet with the overall requirements of structural performances. The debonding failure of hybrid FRP sheets can be also avoided through an appropriate hybrid design. On the other hand, a novel type of FRP-RC hybrid structures as one of new constructions with integrated structural performances is proposed.Then, the flexural or diagonal macro-crack induced debonding failure mechanisms in FRP-strengthened concrete structures are investigated numerically based on nonlinear FEM and fracture mechanics. Moreover, the modeling of long-term behavior such as creep and fatigue of FRP-concrete interface is developed.Finally, a self-sensing manner of FRP-strengthened or FRP-RC hybrid structures is proposed through developing hybrid carbon fiber sensors. Besides, a health monitoring system based on distributed fiber optic sensing techniques is developed to monitor the strengthening effects and other structural performances of FRP-strengthened structures. Less