Fatigue Performance Evolution Analysis Of PC Bridge Based On Damage Accumulation Effect

As the important structure in the field of transportation, the bridge and its members are not only undertaking the transport task, but also are related to the life of us and the property of our country. In the modern times, with the development of the transportation, which is heavier and higher frequency, so the damages from the whole or the local of the bridge are incurred more and more. In this way, the durability and safety of the bridge are payed more attention to and the design, construction, operation and maintenance are investigated and discussed by the bridge engineers and researchers. From the aspect of fatigue accumulated damage of the structures, and from the construction stage to operation stage or the life cycles of the bridge, base on the considering the damage in these fields, the damage effect would be analyzed systematically. Such as stress amplitude and displacement amplitude, the damage effects and fatigue characters from damage would be demonstrated from the determine and fix quantify. The main researches in the thesis are following:(1) Based on the investigating of the bridge in the stage of construction and operation, the current problems in the times and the endangers were introduced by the damage in it. And the fatigue damages and internal damages were emphasized much more. In the other hand, the fatigue characters of the concrete and steel were discussed which are applied widely in the PC bridge.(2) From the various accidents of the bridges in these times, three kinds of reasons were put forward:retrograde strength, retrograde stiffness and retrograde durability and stated defects and phenomenons in the bridge engineerings. The variable quantities of damage the applying principles were raised in the general. From the aspects of three reasons, the foundation of the FEM model of accumulated damages was set up and the working conditions in this model.(3) The above FEM model of accumulated damages was put into the two bridges engineerings, and the working conditions were calculated subtly. Taking the long span rigid frame bridge as the example, effects from the damage about the stress and the deformation were compared and summarized. And take the Huanghe bridge as the other example, especially the abnormal construction stage was considered. So the accumulated damage affection was demonstrated and compared.In the end, the results are valuable in the engineerings.(4) The analysis model of bridge fatigue character with considering the damage was put forward. In the model considering the possible factors that caused the damages, the theory would be the support of the following researches. Based on the statistic analysis of the amount of traffic flow and the accumulated damages theory, the standard traffic truck loading was proposed and applied which was fit for the operation condition in the above FEM model.(5) According to the above model and working conditions, the fatigue evolutional characters of the bridge were analyzed on condition of accumulated damage. Most of all, taking the long span rigid frame bridge as the example, the fatigue ranges curves of stress and deformation were obtained entirety with all kinds of working conditions.The results demonstrate that the parameters of the midspans were sensitive and should be taken seriously.At last, the summary of the thesis and main conclusions were raised.In the following research, the problems and prospects were also raised which are all important in the fatigue damage research task.