After nearly a decade of application and investigation, a motion amplification device with viscous dampers for energy dissipation has been recognized as an effective solution to mitigate wind or seismic excitation, es...After nearly a decade of application and investigation, a motion amplification device with viscous dampers for energy dissipation has been recognized as an effective solution to mitigate wind or seismic excitation, especially for stiff structural systems. As a result of compensation of amplified motion, it has been proved that the efficiency of viscous damper largely depends on the motion amplification device configuration, particularly for device stiflhess. In this paper, a ＂scissor-jack＂ type of motion amplification device, called a ＂toggle brace damper＂ system, is studied. It is demonstrated that the efficiency of such a device reflected by its amplification factor is not merely a function of its geometric configuration, but is highly dependent on the support elements＇ stiffness as well, similar to the mechanism of a leverage arm. Accordingly, a mathematical model in terms of complex modulus of the viscous damper with consideration of the support brace＇s stiffness is established. The results indicate that the efficiency of the motion amplification device with viscous dampers significantly depends on the stiffness of the support elements. Other parameters, such as toggle brace configuration and damping values of the viscous damper, are studied and compared. As an application example, numerical analyses are conducted to study the dynamic performance of a 39-story office tower installed with toggle brace dampers constructed on soft soil in a reclaimed area, under a combined effect of the vortex shedding of an adjacent existing 52-story building and earthquakes. The results show that viscous dampers with a motion amplification system using a properly designed toggle brace device proved to be an effective solution to alleviate the external excitations.展开更多
文摘After nearly a decade of application and investigation, a motion amplification device with viscous dampers for energy dissipation has been recognized as an effective solution to mitigate wind or seismic excitation, especially for stiff structural systems. As a result of compensation of amplified motion, it has been proved that the efficiency of viscous damper largely depends on the motion amplification device configuration, particularly for device stiflhess. In this paper, a ＂scissor-jack＂ type of motion amplification device, called a ＂toggle brace damper＂ system, is studied. It is demonstrated that the efficiency of such a device reflected by its amplification factor is not merely a function of its geometric configuration, but is highly dependent on the support elements＇ stiffness as well, similar to the mechanism of a leverage arm. Accordingly, a mathematical model in terms of complex modulus of the viscous damper with consideration of the support brace＇s stiffness is established. The results indicate that the efficiency of the motion amplification device with viscous dampers significantly depends on the stiffness of the support elements. Other parameters, such as toggle brace configuration and damping values of the viscous damper, are studied and compared. As an application example, numerical analyses are conducted to study the dynamic performance of a 39-story office tower installed with toggle brace dampers constructed on soft soil in a reclaimed area, under a combined effect of the vortex shedding of an adjacent existing 52-story building and earthquakes. The results show that viscous dampers with a motion amplification system using a properly designed toggle brace device proved to be an effective solution to alleviate the external excitations.
文摘目的观察侧弯支具联合矫形鞋垫对青少年特发性脊柱侧弯(AIS)患者脊柱畸形和步行表现改善的效果。方法 2019年9月至2020年9月,门诊AIS患者42例随机分为支具组(n=21)和支具联合矫形鞋垫组(n=21)。两组均每天佩戴支具22~23 h,矫正体操每天1次,每天30 min,共2个月。支具联合矫形鞋垫组在此基础上增加矫形鞋垫干预,每天至少8 h,共2个月。同时,招募32例脊柱发育正常的同龄青少年作为健康组。采用GaitScan仪器采集研究对象步态及足底压力测量数据。先将AIS患者与健康组的步态与足底压力数据进行横向对比,找出异常指标,再进行支具组与支具联合矫形鞋垫组之间脊柱畸形和上述异常指标的比较。结果 AIS组足底压力中心漂移指数(CPEI)高于健康组(F=3.120, P <0.05),AIS组与健康组比较,单足足跟内侧与足跟外侧压力比值(M/L)和全足压力均存在显著性差异(P <0.05);支撑相周期、步行速度、各时相所占比例均不存在显著性差异(P> 0.05)。治疗后,支具组和支具联合矫形鞋垫组Cobb角均显著减小(t>7.552, P <0.001),组间比较无显著性差异(t=0.459, P> 0.05);支具组CPEI、M/L、双侧全足压力比无显著变化(P> 0.05);支具联合矫形鞋垫组CPEI减小(t=2.209, P <0.05),M/L、双侧全足压力比值趋于1(t> 2.306, P <0.05),且优于支具组(|t|> 2.319, P <0.05)。结论 AIS患者可能存在足底压力分布局部及整体不对称改变。加用矫形鞋垫改善AIS患者侧弯畸形的效果有限,但可有效改善AIS患者的异常生物力学,使患者受力趋于平衡。
