Study on Energy-Based Damping Evaluation of Structural Systems

本研究的主要目的是发展一种以能量为基础的方法，以评估结构的阻尼特性，特别是子结构的相互作用。本研究的主要内容如下：1.通过对多田良大桥进行基于ERA的试验模态分析、基于有限元的理论模态分析和基于子结构综合的阻尼分析，研究了大跨度斜拉桥的索振耦合特性及其对模态阻尼特性的影响.应用基于能量的评估方法，在假设梁的内阻尼和支座的摩擦阻尼的基础上，推导出了梁桥模态阻尼的显式计算公式，并用现场振动数据和模型试验数据验证了公式的正确性。通过对2梁和4梁桥梁中混凝土板和钢主梁等下部结构的阻尼贡献的评价，阐明了梁桥的阻尼机理.采用能量法对由两条相同拉索和一条次级拉索组成的拉索系统模型进行了阻尼分析，并与试验结果进行了比较。研究表明，子结构间的内共振可以提高系统的模态阻尼.通过引入基于能量的阻尼器性能指标，研究了用于控制中高层建筑的滞回阻尼器在地震特性变化时的鲁棒性能。研究发现，除了最大输入能量对阻尼器效率的影响外，基于能量的有效持续时间和地震优势周期等时变特性对阻尼器效率也有很大的影响.通过考虑等效复刚度矩阵，研究了结构阻尼矩阵的一般求解方法，但仍处于研究阶段。

The main objective of this study is to develop an energy-based method for evaluating damping characteristics of structures with special reference to sub-structural interaction. The main parts of the present study are summarized as follows.1. The coupled cable-vibration characteristics and its effect on the modal damping characteristics have been investigated for long-span cable-stayed bridges by conducting the experimental modal analysis based on ERA, the theoretical modal analysis based on FEM, and the damping analysis based on sub-structural synthesis for the Tatara Bridge.2. A explicit formula for modal damping of girder bridge has been derived by applying the energy-based evaluation method with an assumption of girder's internal damping and support's friction damping, and its validity has been checked with field vibration data as well as a model experiment data. The damping mechanism of girder bridges has been also clarified by evaluatin damping contributions of substructures such as concrete slab and steel main girder in 2-girders and 4-girders bridges.3. The energy-based damping analysis of a cable system model consisting of two identical cables with a secondary cable was conducted and the results were compared with the experimental ones. It is concluded that the modal damping of system can be made higher by means of internal resonance among substructures.4. Robust performance of hysteretic dampers, used in controlling mid-rise buildings, against change of earthquake characteristics is investigated by introducing an energy-based damper performance index. It is found out that, besides the effect of maximum energy input on damper efficiency, othertime dependant properties as energy-based effective duration and earthquake dominant period have great influence on the damper efficiency.5. A general method for evaluating a damping matrix of structure has been studied by considering an equivalent complex stiffness matrix but is still under investigation.