共查询到18条相似文献，搜索用时 820 毫秒
1.
采用主成分分析法与混沌时间序列分析方法对地震动的非线性特性进行分析,分别从定性与定量的角度考察地震动的非线性特性;探讨了地震动的要素对其混沌特性的影响。结果表明:地震动最大幅值的变化对混沌特性没有影响,而持时、频谱特性、采样频率等要素对混沌的定量指标均产生了影响。 相似文献
2.
为深入研究预制拼装结构的人致振动特性,采用限制结构加速度响应的方法,对某预制拼装人行斜拉天桥的舒适度进行评价.通过在控制点布设加速度传感器,获得结构在环境激励下的振型、自振频率及阻尼比;根据桥面拼接的弹性连接结构特性,确定相邻节段间的弹性连接刚度;参照国内外相关规范,建立行人和车辆通行荷载分析模型,获得各种荷载工况下的峰值加速度,分析人行天桥的舒适度.结果表明：结构的自振频率和峰值加速度与实测值吻合良好,从而验证了有限元分析模型的有效性;考虑预制拼装对结构刚度的折减可以更真实地反应结构的振动特性,预制拼装结构的舒适度评价指标与整体式结构一致;人群质量对该结构振动频率的影响较小,可以不考虑人群荷载与车辆通行荷载的耦合作用;车辆通行荷载对结构的舒适度产生一定程度的影响. 相似文献
3.
《实验室研究与探索》2013,(10)
混沌技术在通信领域中具有重要的应用价值,在混沌通信系统中,由于通信类型不同得出的性能指标也不同。文中以寻找合适的混沌模型使通信系统的性能指标达到最佳为出发点,利用Matlab技术构造一种新三维混沌系统,基于幅值同步技术快速实现混沌遮掩通信,给出对比效果图;同时与其他混沌系统对比,得出新系统相比其他系统更适合四进制多因子参数扩频技术混沌通信。文中首先通过Matlab分析系统的平衡点、分岔图、相关性、混沌吸引子等特性,再通过幅值实现同步,并与非线性同步性能作比较,得出幅值同步简单、响应快、误差小等优点,同时进行了掩膜通信验证;最后将本系统与其他混沌系统分别基于变参数扩频技术进行仿真对比,得出二四进制误码率的结果。 相似文献
4.
颜桂云余勇胜袁宇琴李环辉张东鹏 《福建工程学院学报》2021,(4):307-314
根据远场类谐和地震动、普通地震动反应谱与规范反应谱之间的包络关系,选取输入结构的地震动加速度峰值?建立双柱墩式抗震梁桥,分析同峰值加速度的远场类谐和地震动和普通地震动作用下双柱墩式梁桥主梁、墩柱的地震响应等,揭示远场类谐和地震动作用下双柱墩式梁桥的动力响应与失效机理?采用SR模型模拟双柱墩抗震梁桥墩底的SSI效应,分析远场类谐和地震动作用下梁桥地震响应变化规律。结果表明,远场类谐和地震动对桥梁的地震响应为普通地震动作用的1.5倍以上,其设防烈度至少应提高一度才能保证桥梁的安全?墩-系梁连接点处弯矩随桩土刚度减小而增大,有可能会引起桥墩弯曲破坏。 相似文献
5.
Yang Jihua 《大连大学学报》1992,(4)
本文对开孔(水工)结构进行了结构动力特性和规则波作用下结构动力响应的模型试验,并用有限元法计算了结构自振特性,分析了3种水位、不同波高、周期情况下结构的动力特性和结构的动力响应. 相似文献
6.
分别以外加周期信号的幅度和频率为参变量,改变两个参数仿真计算杜芬混沌系统的运动状态,确定了杜芬混沌系统状态运动特征与外加干扰信号之间的关系,仿真结果说明周期信号幅度与频率是影响杜芬振子状态的主要因素.本文还将系统在外加周期信号与随机信号干扰的运行结果进行了分析比较,结果表明混沌系统对噪声的干扰具有免疫力. 相似文献
7.
以一类金融混沌系统为例,提出了一个驱动系统对应多个响应系统的广义投影同步方法,实现了驱动-响应-响应系统之间的同结构广义投影同步,以及三个类型完全不同的混沌系统的异结构广义投影同步。通过改变广义投影同步的比例因子,获得了任意比例于原驱动混沌系统输出的混沌信号,数值仿真验证了此方法的有效性。 相似文献
8.
综合考虑齿轮时变啮合刚度、齿面间隙、轴承游隙和啮合综合误差等多种非线性因素影响,建立三自由度直齿轮振动模型,并对模型进行无量纲化处理。采用4阶变步长Runge－Kutta法对齿轮模型微分方程进行求解,得到齿轮在轴承径向游隙变化时运动的分岔图、相图和Poincaré映射图。发现随着轴承游隙的变小,系统响应也经历了从混沌态到稳态再到混沌态的历程,其中发生了倍周期分岔的现象。给出了系统的分岔值,得到了系统混沌形成的过程。 相似文献
9.
为了研究地铁荷载作用下饱和粉性土的孔隙水压力特性,针对上海地铁10号线国权路附近的饱和粉性土进行多功能GDS循环三轴试验,考虑了振动频率、动应力幅值及固结比等因素对孔隙水压力的影响。试验结果表明:土体遭受地铁振动荷载作用下,孔隙水压力经过三个阶段的变化过程,即快速增长-缓慢增加-衰减稳定。相同振动频率及固结比条件下,动应力幅值越大,产生的孔隙水压力越大;相同动应力幅值及固结比条件下,频率越小,产生的孔隙水压力越大;相同动应力幅值及振动频率条件下,固结比越大,产生的孔隙水压力越大。采用单因素设计法及方差分析,得到振动频率、动应力幅值及固结比等因素均对孔隙水压力有非常显著的影响。 相似文献
10.
给出一种基于广义混沌序列的多幅图像隐藏算法.利用图像的迭代混合可以将多幅图像隐藏于一幅图像之中,借助Logistic混沌动力学系统过程既非周期又不收敛,且对初始条件敏感性,产生实数值混沌序列,利用该混沌序列生成广义混沌序列,作为隐藏算法的混合因子,提高了隐藏算法的安全性.数值实验结果表明,算法简单易行,安全性好. 相似文献
11.
Most reinforced concrete(RC)frame structures did not achieve the "strong column-weak beam" failure mode in recent big earthquakes, resulting in a large number of casualties and significant property loss. To deal with this serious problem, a new column-beam relative factor was proposed to characterize the relative yield situation of column ends and beam ends. By limiting the column-beam relative factor, RC frame structures could achieve the "strong column-weak beam" failure mode under the excitation of strong ground motions. The limit values of column-beam relative factor were calculated, analyzed and verified by using structural simulation models for corner columns in the bottom story of structures, which are destroyed most seriously in earthquakes. The results show that the limit values should be analyzed under bi-directional ground motion and with different axial compression ratios of columns. The peak ground acceleration(PGA)of ground motions has no significant effect on the limit values, while the type of strong ground motions has a significant effect on the limit values. 相似文献
12.
Izuru Takewaki 《浙江大学学报(A卷英文版)》2011,12(5):327-334
On March 11, 2011, eastern Japan was shaken by the 2011 off the Pacific coast of Tohoku Earthquake (the Great East Japan Earthquake).
Almost 30 000 people have been killed or are missing as a result of that earthquake and the subsequent monster tsunami, as
of April 11, 2011. This paper reports several aspects of this devastating earthquake. It has been reported that long-period
ground motions, which had been predicted by many researchers, occurred in Tokyo, Nagoya and Osaka. The response characteristics
of high-rise buildings to the recorded long-period ground motions are discussed from the viewpoint of resonance and critical
excitation. It is shown that high-hardness rubber dampers are very effective in the reduction of vibration duration in addition
to the reduction in vibration amplitude. 相似文献
13.
This study introduces measures to identify resonant （concentration of energy in a single or a few frequencies） or unfavorable earthquake ground motions. Probabilistic measures based on the entropy rate and the geometric properties of the power spectral density function （PSDF） of the ground acceleration are developed first. Subsequently, deterministic measures for the frequency content of the ground acceleration are also developed. These measures are then used for identifying resonance and criticality in stochastic earthquake models and 110 acceleration records measured at rock, stiff, medium and soft soil sites. The unfavorable earthquake record for a given structure is defined as the record having a narrow frequency content and dominant frequency close to the structure fundamental natural frequency. Accordingly, the measures developed in this study may provide a basis for selecting records that are capable of producing the highest structural response. Numerical verifications are provided on damage caused to structures by identified resonant records. 相似文献
14.
为了考察地震动加速度反应谱的统一性,用2种标定周期(反应谱卓越周期Tp和平滑化反应谱卓越周期To)分别对传统规准反应谱的横坐标进行规准化.考虑场地条件和断层距的影响,对集集地震近600水平向分量地震动5%阻尼比的规准反应谱和2种双规准反应谱进行了分析.结果表明场地条件和断层距对规准谱的影响明显,但对2种双规准谱的影响甚小.离散性分析表明对规准反应谱横坐标的规准化得到的双规准谱具有离散性小的特点.最后,对标定周期(Tp,To)的分布进行了参数分析并与以往结果进行了比较.地震动反应谱和标定周期的新特性可以为规范设计谱的应用和发展提供参考依据. 相似文献
15.
马莉 《兰州石化职业技术学院学报》2011,11(4):29-31
在一类含间隙多自由度动力系统的力学模型的基础上,根据系统在无碰撞情况下的无量纲微分方程和相应的无量纲冲击方程,利用龙格一库塔数值仿真方法揭示了系统存在复杂的混沌运动行为。理论分析了延迟反馈方法对混沌控制的有效性,相图和时间历程图均表明该方法能将系统的混沌行为有效地控制到周期轨道。 相似文献
16.
Collapses of transmission towers were often observed in previous large earthquakes such as the Chi-Chi earthquake in Taiwan
and Wenchuan earthquake in Sichuan, China. These collapses were partially caused by the pulling forces from the transmission
lines generated from out-of-phase responses of the adjacent towers owing to spatially varying earthquake ground motions. In
this paper, a 3D finite element model of the transmission tower-line system is established considering the geometric nonlinearity
of transmission lines. The nonlinear responses of the structural system at a canyon site are analyzed subjected to spatially
varying ground motions. The spatial variations of ground motion associated with the wave passage, coherency loss, and local
site effects are given. The spatially varying ground motions are simulated stochastically based on an empirical coherency
loss function and a filtered Tajimi-Kanai power spectral density function. The site effect is considered by a transfer function
derived from 1D wave propagation theory. Compared with structural responses calculated using the uniform ground motion and
delayed excitations, numerical results indicate that seismic responses of transmission towers and power lines are amplified
when considering spatially varying ground motions including site effects. Each factor of ground motion spatial variations
has a significant effect on the seismic response of the structure, especially for the local site effect. Therefore, neglecting
the earthquake ground motion spatial variations may lead to a substantial underestimation of the response of transmission
tower-line system during strong earthquakes. Each effect of ground motion spatial variations should be incorporated in seismic
analysis of the structural system. 相似文献
17.
Numerical simulation on floating behavior of buoyancy tank foundation of anemometer tower 总被引：1，自引：0，他引：1
The intact stability and damage stability of a model of an anemometer tower with buoyancy tank foundation are computed by the finite element software MOSES in this paper. The natural period of the anemometer tower is discussed through frequency domain analysis. The influence of a single factor, such as towing point position, wave height, wave direction and wave period, on towing stability is discussed through time domain analysis. At the same time, the towing stability under the condition of various combinations of many factors is analyzed based on the meas- ured data of the target area. Computer simulation results show that the intact stability is preferable and the damage stability is sufficient under the condition of plenty of subdivisions. Within the scope of the buoyancy tank foundation, the higher the towing point position is, the better the stability is. Wave height has a great impact on the motion amplitude of buoyancy tank foundation, but the effect on the acceleration is not obvious; wave period has a great impact on the acceleration, while the effect on the motion amplitude is not obvious; following-waves towing is more conducive to safety than atry. 相似文献
18.
利用QLVC-ZSA1振动信号分析仪及加速度传感器,对数控车床在不同切削要素的车削过程中刀具的振动响应进行了测试及量化研究,得到了刀具振动加速度信号的时域曲线及自功率谱密度曲线。研究表明:刀具的振动响应是一个随车削进行的时变过程,在同一走刀相同车削要素的车削过程中,随着去除材料的增加,刀具所受的激振能量减少;随着切削深度的增加,刀具振动的最大自功率谱密度并非单调增加,车削深度对于刀具振动的影响存在一个临界值;随着主轴转速及进给速度的提高,刀具振动的自谱密度值随之增大,而相应的振动频率降低。 相似文献