大跨度悬索桥多模态涡振的阻尼器半主动控制方法研究

There exits a number of vertical bending modes with frequerncy less than 0.6Hz for long-span suspension bridges, and severe multi-mode vertical vortex-induced vibration (VVIV) has been observed on several steel box-girder suspension bridges under frequent wind velocities. For a finished bridge, it is difficult to suppress the multi-mode VVIV by additional aerodynamic measurements or tuned mass dampers. It has been found by the applicant in the previous study that for the multi-span suspension bridge the floating type pylon-girder connection is frequently used, in this case there is a relative displacement between the girder and the pylon when VVIV occurs, so the damping device installed between the girder and the pylon is able to suppress multi-mode VVIV. However, optimal control for multi-mode VVIV can not be achieved by a passive damping device. Since the damping device is just installed between the pylon and the girder, semi-active control of the VVIV for multiple modes is feasible. In this application, the semi-active control of the multi-mode VVIV using the damping device installed between the pylon and the girder will be studied, through the theoretical analysis, numerical simulation and experimental verification. To achieve this goal, the following contents will be deeply investigated: First, the characteristics of the VVIV of different modes will be studied, as well as the optimal control parameters of the damping device. Second, the effective semi-active control strategy will be proposed for the multi-mode VVIV control. Third, the hybrid axial eddy current damper employing both the permanent magnets and the electromagnets will be developed and served as the semi-active damper.

大跨度悬索桥频率在0.6Hz以内竖弯模态密集，国内外多个既有悬索桥在常遇风速下加劲梁多个模态都相继发生了较为严重的竖向涡激振动。在既有悬索桥上追加气动措施或附加TMD措施抑制多阶涡振都有较大的困难。申请人在前期工作中发现：多跨悬索桥一般为漂浮体系，涡振时在主塔和加劲梁相交处有相对位移；在此处安装竖向阻尼器对多阶模态涡振都有抑制效果；但参数固定的阻尼器无法实现多个模态的最优控制。注意到集中安装在塔梁相交处的阻尼器具备实施半主动控制的可行性，申请人将采用理论分析、数值模拟和试验验证相结合的方法研究采用塔梁相交处阻尼器进行半主动控制的方法，实现对多个模态涡振的最优抑制效果。为此，必须掌握不同模态竖向涡振的特征参数与所需的阻尼器最优控制参数；研究建立高效率的多模态竖向涡振半主动控制方法；研发可以执行半主动控制的永磁-电磁混合式轴向电涡流阻尼器。

近年来，国内外多座既有悬索桥在常遇风速下遭遇了较为严重的多模态竖向涡振，由此引发的行车安全和舒适性问题对大桥的正常运营造成了不利影响。在既有悬索桥上追加气动措施或附加TMD措施抑制多阶涡振都有较大的困难。本项目研究在桥塔和主梁交汇，二者存在相对竖向位移的位置设置竖向阻尼器的悬索桥多模态竖向涡振被动和半主动控制方法。本项目的工作如下：（1）针对节段模型涡振试验，研制了一种阻尼系数可调的板式电涡流阻尼器。试验表明它可为节段模型弹性悬挂系统提供连续、精确可调的线性粘滞阻尼，最大附加阻尼比2.0%以上；（2）精确识别了开口断面加劲梁竖向涡振锁定区间、最大涡振振幅以及对应的Scanlan非线性涡激力数学模型的气动参数随Sc数的变化规律。研究表明，主梁竖向涡振振幅和锁定风速区间都随着Sc数的增大而逐渐减小，但影响规律因风攻角而异；选取四到五组较小的Sc数开展风洞试验，利用Scanlan非线性涡激力模型可以预测桥梁最大涡振振幅随Sc数的变化规律；（3）研究了安装竖向阻尼器对大跨度悬索桥涡振敏感模态附加阻尼比的影响。理论分析表明，通过参数优化，被动式竖向阻尼器可显著提高悬索桥高阶竖弯模态的固有阻尼比，理想条件下可达1%以上；（4）研制了电磁轴向电涡流阻尼器样机并开展了性能测试，试验结果表明通过改变安匝数可有效调节轴向电涡流阻尼器的阻尼系数。（5）结合悬索桥有限元模型的动力响应分析方法研究了bang-bang半主动控制算法对加劲梁多竖向涡振的控制效果。结果表明，对于指定的高阶竖弯模态，半主动控制比被动控制效果更优；（6）开展了悬索桥等效气弹模型的涡振特性试验。结果表明，气弹模型不同竖弯模态的涡振响应随着结构阻尼比的增大而降低。

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