作为一类具有非线性刚度的典型非线性被动控制装置,非线性能量阱(nonlinear energy sinks,NESs)以其质量轻、频率鲁棒性强等优势引起了工程领域的广泛关注。目前,针对耦合NES的结构系统动力学研究主要是确定性载荷情形,仅少数涉及随机...作为一类具有非线性刚度的典型非线性被动控制装置,非线性能量阱(nonlinear energy sinks,NESs)以其质量轻、频率鲁棒性强等优势引起了工程领域的广泛关注。目前,针对耦合NES的结构系统动力学研究主要是确定性载荷情形,仅少数涉及随机激励情形的研究。该文章研究了随机激励下耦合NES的单自由度(single-degree-of-freedom,SDOF)结构随机振动的参数优化问题。首先应用加权残值法,将原系统等效为具有精确平稳解的随机动力学系统,理论解和蒙特卡洛解模拟(Monte Carlo solution,MCS)在误差允许范围内吻合,显示所提的数值方法有效;然后利用原系统的平稳响应概率密度函数(probability density function,PDF)的近似解析表达式来构造目标函数,提出了一种以主结构位移与速度响应量均方(mean-square,MS)最小为目标的NES参数优化设计策略,讨论了非线性能量阱的阻尼系数、非线性刚度系数、质量比等参数对减振性能的影响。结果表明,增加NES的质量比与阻尼系数,可以实现较强的减振性能,非线性刚度值对NES的减振性能的影响规律与质量比取值相关。相关工作可为NES的设计与应用提供参考。展开更多
The fiber reinforced concrete has good dynamic mechanical properties. But corresponding research lacks the dynamic damage characteristics of the polypropylene fiber(fiber of low elastic modulus) and steel fiber(fib...The fiber reinforced concrete has good dynamic mechanical properties. But corresponding research lacks the dynamic damage characteristics of the polypropylene fiber(fiber of low elastic modulus) and steel fiber(fiber of high elastic modulus) reinforced concrete under medium strain rate(10-6 s-1-10-4 s-1). In order to study the effect of strain rate on the damage characteristics of fiber reinforced concrete during the full curve damage process, the real time dynamic acoustic emission(AE) technique was applied to monitor the damage process of fiber reinforced concrete at three strain rates. The AE wavelet energy spectrum in ca8 frequency band and average AE peak frequency at three strain rates were analyzed. With the accumulation of damage, the AE wavelet energy spectrum in ca8 frequency band increased first and then decreased, and the average AE peak frequency increased gradually. With the increase of strain rate, the AE wavelet energy spectrum in ca8 frequency band and average AE peak frequency decreased gradually. The polypropylene fiber content has more obvious effect on the Dynamic increase factor(DIF) of the peak stress than the steel fiber content. The theoretical basis was provided for the monitoring of dynamic damage of fiber reinforced concrete based on the AE technique.展开更多
文摘作为一类具有非线性刚度的典型非线性被动控制装置,非线性能量阱(nonlinear energy sinks,NESs)以其质量轻、频率鲁棒性强等优势引起了工程领域的广泛关注。目前,针对耦合NES的结构系统动力学研究主要是确定性载荷情形,仅少数涉及随机激励情形的研究。该文章研究了随机激励下耦合NES的单自由度(single-degree-of-freedom,SDOF)结构随机振动的参数优化问题。首先应用加权残值法,将原系统等效为具有精确平稳解的随机动力学系统,理论解和蒙特卡洛解模拟(Monte Carlo solution,MCS)在误差允许范围内吻合,显示所提的数值方法有效;然后利用原系统的平稳响应概率密度函数(probability density function,PDF)的近似解析表达式来构造目标函数,提出了一种以主结构位移与速度响应量均方(mean-square,MS)最小为目标的NES参数优化设计策略,讨论了非线性能量阱的阻尼系数、非线性刚度系数、质量比等参数对减振性能的影响。结果表明,增加NES的质量比与阻尼系数,可以实现较强的减振性能,非线性刚度值对NES的减振性能的影响规律与质量比取值相关。相关工作可为NES的设计与应用提供参考。
基金Funded by the National Natural Science Foundation of China(No.51009058)Postdoctoral Science Foundation of China(No.2011M501160)+1 种基金the University Natural Science Research Project of Jiangsu Province(No.13KJD560002)the Doctoral Research Start-up Fund of Jinling Institute of Technology(No.Jit-b-201321)
文摘The fiber reinforced concrete has good dynamic mechanical properties. But corresponding research lacks the dynamic damage characteristics of the polypropylene fiber(fiber of low elastic modulus) and steel fiber(fiber of high elastic modulus) reinforced concrete under medium strain rate(10-6 s-1-10-4 s-1). In order to study the effect of strain rate on the damage characteristics of fiber reinforced concrete during the full curve damage process, the real time dynamic acoustic emission(AE) technique was applied to monitor the damage process of fiber reinforced concrete at three strain rates. The AE wavelet energy spectrum in ca8 frequency band and average AE peak frequency at three strain rates were analyzed. With the accumulation of damage, the AE wavelet energy spectrum in ca8 frequency band increased first and then decreased, and the average AE peak frequency increased gradually. With the increase of strain rate, the AE wavelet energy spectrum in ca8 frequency band and average AE peak frequency decreased gradually. The polypropylene fiber content has more obvious effect on the Dynamic increase factor(DIF) of the peak stress than the steel fiber content. The theoretical basis was provided for the monitoring of dynamic damage of fiber reinforced concrete based on the AE technique.