多频率拟合法测在役预应力空间结构拉索索力的研究

发布时间：2018-04-04 04:50

本文选题：索力测试　切入点：多频率拟合　出处：《辽宁工程技术大学》2014年硕士论文

【摘要】：结构健康监测系统是确保预应力大跨度空间结构安全建造和健康营运的一个重要保障手段,也可以对极端条件下结构可能出现的失效进行预警从而最大程度地减少人员和财产损失。预应力大跨度空间结构在建造和运营期间的外部荷载作用(风、地震、温度等)以及结构外部荷载作用效应(位移、加速度、应力、裂缝等)是判断结构是否健康的重要指标,也是结构健康监测的重要内容。预应力大跨度空间结构形式主要有预应力网格结构、斜柱网格结构、索穹顶结构、张弦梁结构等,预应力拉索在这些结构中,施工张拉完成后初始状态索力是否达到设计目标、使用阶段索力是否符合设计要求、灾害发生后结构的索力和内力水平等直接关系到结构的安全性。预应力拉索的施工过程中,索的张拉(特别是分批张拉)会使拉索之间相互影响：每一次张拉几乎都会使先前张拉的索力发生变化,使结构索力偏离设计值,造成索力的失控。拉索在使用过程中,即在役预应力拉索会发生松弛和损伤从而导致应力损失,造成索力的失控。索力失控带来不可知的结构内力重分布,甚至造成整个结构的失效,预应力拉索结构索力的精确测量是保障工程安全的关键性技术。当前,预应力拉索施工过程中采用的有压力表测试法和压力传感器法测索力,基本上能够保证测试精度要求。在役拉索索力测量方法有压力传感器法、力平衡法、频率法(振动法)、磁通量法、光纤光栅等。压力传感器法须在每根拉索的锚固端安装一个压力传感器,花费很大；力平衡法只对截面较小的柔性索有较高的测量精度；磁通量法需预先将传感器穿在拉索上,对于没有预埋传感器的拉索不能应用该法；光纤光栅法由于成本太高不适用在役拉索的检测。因此,从经济和技术等方面考虑,频率法具有测试仪器日趋小型化,携带方便,容易安装,可以重复使用的优点,并且其测试精度高,因此频率法师目前索力测试的最佳选择。针对预应力拉索结构工程中短粗索和多跨索索力测试困难的问题,本文对基于频率法原理的索力测试理论进行了深入研究,提出了基于正弦激振的多频率拟合法。首先对不同的边界条件和索刚度条件的索振动动力模型进行求解,并推导出索力计算公式；然后通过对张弦梁结构拉索进行计算,并分析结果,验证了多频率拟合法的适用性；最后基于理论成果研制了拉索安全监测系统。
[Abstract]:Structural health monitoring system is an important means to ensure the safe construction and healthy operation of prestressed long-span spatial structures.The possible failure of structures under extreme conditions can also be forewarned to minimize the loss of personnel and property.The external loads (wind, earthquake, temperature, etc.) and the external load effects (displacement, acceleration, stress, cracks, etc.) of prestressed long-span spatial structures during construction and operation are important indexes to judge the health of structures.It is also an important part of structural health monitoring.There are prestressed grid structure, oblique column grid structure, cable dome structure, beam string structure and so on. In these structures, whether the initial state cable force reaches the design goal after the construction of tensioning is completed,Whether the cable force meets the design requirements at the stage of use, the cable force and internal force level of the structure after the disaster are directly related to the safety of the structure.In the construction process of prestressed cable, the cable tension (especially the batch tension) will make the cable affect each other: each tension will almost make the cable force of the previous tension change, make the structural cable force deviate from the design value, cause the cable force out of control.In the process of using the cable, that is, the pre-stressed cable in service will be relaxed and damaged, which will lead to stress loss, resulting in the loss of cable force.The loss of cable force leads to the unknowable redistribution of internal forces and even the failure of the whole structure. The accurate measurement of the cable force of prestressed cable structure is the key technology to ensure the safety of engineering.At present, the pressure gauge test method and the pressure sensor method are used to measure the cable force in the construction process of the prestressed cable, which can basically ensure the precision of the test.In service cable force measurement methods include pressure sensor method, force balance method, frequency method (vibration method, magnetic flux method, fiber grating and so on).The pressure sensor method is required to install a pressure sensor at the anchoring end of each cable, which is costly; the force balance method has higher measurement accuracy only for flexible cables with a smaller section; and the magnetic flux method requires the sensor to be worn in advance on the cable,The method can not be applied to cables without embedded sensors, and the FBG method is not suitable for the detection of in-service cables because of its high cost.Therefore, in terms of economy and technology, the frequency method has the advantages of miniaturization, convenient carrying, easy installation, and high precision of test, so the frequency magician is the best choice for cable force test at present.In order to solve the problem of short thick cable and multi-span cable force measurement in prestressed cable structure engineering, the theory of cable force measurement based on frequency method is studied in this paper, and the multi-frequency fitting method based on sinusoidal vibration is proposed.At first, the dynamic model of cable vibration with different boundary conditions and cable stiffness conditions is solved, and the calculation formula of cable force is deduced, and the applicability of multi-frequency fitting method is verified by calculating the cable strands of beam string structure and analyzing the results.Finally, based on the theoretical results, the cable safety monitoring system is developed.
【学位授予单位】：辽宁工程技术大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU399;TU317

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