RESEARCH ON DYNAMIC RESPONSE ANALYSIS AND CABLE FORCE IDENTIFICATION METHOD OF SUBMERGED ANCHOR CABLES
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摘要: 海洋资源和海洋空间的开发利用是21世纪人类发展海洋的两大主题. 锚索作为海洋装备和深海建筑的重要承力和锚固构件, 其损伤和破坏将直接影响整个结构的安全性和耐久性, 因此有必要对锚索的服役期状态进行实时监测和评估. 索力是反映锚索静动力学特性的重要物理量, 掌握索力的实时变化情况对于锚索的健康监测及状态评估具有重要意义. 现有研究通常在张紧弦或简支梁模型的基础上, 采用修正索力公式或智能优化算法来识别索力, 未能充分考虑垂度引起的几何非线性影响. 为了在理论上给出物理意义更加明确、识别精度更高的锚索索力识别公式, 针对水下锚索的几何非线性及阻尼非线性特点, 首先利用等效线性化技术, 推导了锚索自由振动频率和响应的摄动解, 给出了考虑锚索垂度的频率解析表达式; 在此基础上给出了基于振动法的索力识别方案; 数值案例表明本文方法识别结果与真实值一致, 从而验证了本文方法的准确性. 相关理论和结论能够为此类工程结构的动力分析和健康监测提供理论依据.Abstract: The development and utilization of marine resources and space are two major themes of human development of the ocean in the 21st century. As an important force-supporting and anchoring component of marine equipment and deep-sea structures, the damage and destruction of anchor cable will directly affect the safety and durability of the whole structure, so it is necessary to monitor and evaluate the service state of anchor cable in real time. Cable force is an important physical quantity reflecting the static and dynamic characteristics of anchor cable. It is of great significance to master the real-time change of cable force for the health monitoring and state assessment of anchor cable. The existing researches usually use modified cable force formula or intelligent optimization algorithm to identify cable force on the basis of tension string or simply supported beam model, but fail to fully consider the geometric nonlinearity caused by sag. In order to give a more explicit physical meaning and more accurate identification formula of anchor cable force in theory, aiming at the geometric nonlinearity and damping nonlinearity of underwater anchor cable, firstly, the perturbation solution of free vibration frequency and response of anchor cable is derived by using equivalent linearization technique, and the analytical expression of frequency considering sag of anchor cable is given. On this basis, the cable force identification scheme based on vibration method is given. Numerical examples show that the recognition results of this method are consistent with the real values, thus verifying the accuracy of this method. The relevant theories and conclusions can provide theoretical basis for dynamic analysis and health monitoring of such engineering structures.
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表 1 索力识别迭代过程
Table 1. Iteration of cable force identification
Step ${H_0}$/kN $\eta $ $\bar H/{\rm{kN}}$ 1 4197 4.2648 4051 2 4051 4.5853 4040 3 4040 4.5853 4040 -
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