Research On Energy Dissipation Mechanisms Of The Fiber Structure In Fiber Reinforced Concrete

Concrete structures are commonly used in Civil Engineering infrastructures. Therefore it has been drawing research on improving of their dynamic characteristics. Many investigations have shown both an increase in energy dissipation and. an improving of dynamic properties of those concrete structures under dynamic loading with addition of fibers. Thus conducting research on the roles played by the fiber structure part in the energy dissipation process is of significance importance to material designing.The dynamic characteristics of the structure or the structure element are a direct reflection of its energy dissipation ability. Based on the previous related works, this thesis is mainly concerned with the wavy fiber structures that have relatively many design variables, and their effects on the dynamic properties of their reinforcing systems were studied. First a general wave propagation model that can model wave propagation in composites reinforced with different fiber structures is introduced, for which then numerical solution is developed and written with computer language to study the fiber structure's effect on the propagating waves. The results are explanative to the energy loss during vibration as well as wave propagation that can include seismic waves, ultrasonic waves and impulse waves. Followed, a finite element cantilever reinforced with different fiber structures was modeled using ANSYS program, in which the viscous damping was considered that has different damping direction for different fiber structures. Then the nature dynamic properties were computed for the model to study the role of the fiber structure. In the end of this thesis, the analysis results and its conclusions were verified by the complementary experimental results.By the works above have done, this thesis have the following conclusions: (1) Fiber structures' effects on the dynamic properties and wave propagation depend upon the modes excited. (2) Fiber structures influence the order of modes excited, thus finally the response of the system under dynamic loading. (3) The wave propagation in composites reinforced with wavy fiber structures is dispersive. As a whole, it obeys the "stiffness law". (4) When the distance between two neighboring nodes of vibration (standing waves) or the wave length of a propagating wave is far less than the wavy fiber's wave length, then "stiffness law" holds, but if the other way around, and then exist a combination process between the vibration waves and the wavy fiber waves. (5) The curved angle variable of the wavy fiber structure have much more apparent effects on the dynamic performance of the system than the fiber wave length variable, thus it is more controllable and has more practicability of optimization.