共查询到19条相似文献,搜索用时 171 毫秒
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研究了震级频度关系式中非线性项产生的原因,指出由于地震孕育过程是非线性的,很多地震现象都服从分形和混沌规律,因此传统的震级频度关系式中应含有非线性项,才能全面描述地震过程的非线性规律.得出了新的含有非线性项的震级频度关系式.讨论了该公式中非线性项的含义. 相似文献
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非线性问题的逐次线性化方法的每个线性化过程可通过最小二乘QR分解算法求解.为了精确地描述和控制逐次线性化迭代过程,引入迭代阻尼系数.首先根据模型拟合表最小的准则确定满足最佳一次线性化效果的最佳初始迭代阻尼系数;然后随遂次线性化迭代而减小迭代阻尼系数,并加入松弛因子对每次迭代输出的波速修正量进行控制;最后根据混沌理论,采用Lyapunov指数和模型拟合差的变化,描述第k次迭代所处的状态,在解估计的方差急增之前及时停止迭代,获得可信度和分辨率最佳的解估计.模型计算与实例证明方法有效. 相似文献
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为研究隔震、减震装置非线性恢复力特性对2自由度主次结构体系均方根位移反应的影响规律,以隔震、减震装置微分型恢复力模式的滞回参数为变量,地震地面运动模拟成高斯白噪声过程,利用等效线性化方法得到主体结构和二次结构均方根位移反应的表达式.分析表明,主体结构隔震装置非线性恢复力特征对主、次结构的均方根位移反应的影响占主导地位;隔震、减震装置的恢复力特征产生适度非线性有利于减小主、次结构的均方根位移反应. 相似文献
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本文从哈密顿原理出发,讨论磁尾中性片中粒子受晨昏起伏电场的影响问题,并把它归结于讨论标准映射的性质.中性片本身是非线性系统,外加起伏场会导致其进入混沌状态.本文计算了进入该状态的临界电场E_c以及不同E下的粒子轨迹.计算表明,观测到的晨昏电场可以使离子进入混沌状态,但远小于电子的临界场值.这样离子运动是随机的,电子运动是规则的.仅对离子的随机加热可能是导致中性片中离子温度高于电子温度的原因. 相似文献
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极低屈服点软钢阻尼器恢复力模型的研究 总被引:3,自引:0,他引:3
本文通过试验和理论分析探讨极低屈服点软钢阻尼器的恢复力特性。随着塑性变形的发展将恢复力模型中的骨架曲线进行平移,其卸载曲线用Ramberg—Osgood函数来描述,由此得到的恢复力模型定义为骨架平移模型,将其应用于描述极低屈服点软钢阻尼器的恢复力特性、为了验证该馍型的有效性并确定合理的参数,对安装极低屈服点软钢阻尼器的3层钢框架结构进行了拟动力试验.同时用该骨架平移模型模拟极低屈服点软钢阻尼器的恢复力特性进行了大量的弹塑性地震反应分析,通过取用不同平移系数时的数值计算结果与拟动力试验结果的比较,发现平移系数为0.6左右时,该模型具有较高的精度。 相似文献
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研究地震和岩石破裂现象的非线性科学方法 总被引:3,自引:0,他引:3
本文以地震孕育和岩石破裂过程的阶段(包括裂纹系形成、变形局部化和断层形成、断层活动和松弛)为线索,阐述了非线性科学方法(包括分形几何学,自组织临界现象和混沌动力学)的应用,提出了地震孕育过程和岩石破裂各阶段的普适性特征、机理和要着重研究的课题. 相似文献
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Shuenn-Yih Chang 《地震工程与工程振动(英文版)》2011,10(3):437-451
Although the step degree of nonlinearity has been introduced to conduct basic analysis and error propagation analysis for the pseudodynamic testing of nonlinear systems, it cannot be reliably used to select an appropriate time step before performing a pseudodynamic test. Therefore, a novel parameter of instantaneous degree of nonlinearity is introduced to monitor the stiffness change at the end of a time step, and can thus be used to evaluate numerical and error propagation properties for nonlinear systems. Based on these properties, it is possible to select an appropriate time step to conduct a pseudodynamic test in advance. This possibility is very important in pseudodynamic testing, since the use of an arbitrary time step might lead to unreliable results or even destroy the test specimen. In this paper, guidelines are proposed for choosing an appropriate time step for accurate integration of nonlinear systems. These guidelines require estimation of the maximum instantaneous degree of nonlinearity and the solution of the initial natural frequency. The Newmark explicit method is chosen for this study. All the analytical results and the guidelines proposed are thoroughly confirmed with numerical examples. 相似文献
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Nonlinear dynamics of level variations in the Caspian Sea 总被引:2,自引:0,他引:2
Caspian Sea level variations, which have several equilibrium states, are studied by the methods of the theory of nonlinear dynamic systems. Normal monthly values of sea level according to data collected at Makhachkala gauge from 1900 to 2000 are considered. The diagnostic characteristics of dynamic chaos are used to show that sea level variations have some properties of series with chaotic behavior. A model of level variations in the Caspian Sea, comprising a system of water balance equations for the sea basin, the dynamics of river runoff, and water balance of the sea itself, is proposed. Equation of a nonlinear oscillator is derived and shown to have solutions with chaotic regimes at some combinations of parameters. 相似文献
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强随机噪声干扰是导致地震勘探资料低信噪比的主要原因,如何在强随机噪声干扰下获取有效的信息是值得关注的问题.Duffing振子混沌系统是一个非线性的动力学系统,其对强随机噪声具有免疫能力,而对特定的周期性信号具有敏感性.本文提出一种基于Duffing振子混沌系统的速度分析方法.对CMP道集按照时距曲线关系进行移动窗口截取,将所截取的信号构建为待测信号加入Duffing振子混沌系统,通过相图网格分割方法(GPM)判断系统状态的改变,从而在强随机噪声背景下获得高分辨率的速度谱.理论模型和实际资料的处理结果表明,与传统的水平叠加速度分析方法相比,本方法能够在强随机噪声背景下获得更准确的速度分析结果. 相似文献
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Performance‐based seismic assessment of conventional and base‐isolated steel buildings including environmental impact and resilience
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Sustainability and resilience are issues that are recognized worldwide, and increased attention should be placed on strategies to design and maintain infrastructure systems that are hazard resilient, damage tolerant, and sustainable. In this paper, a methodology to evaluate the seismic sustainability and resilience of both conventional and base‐isolated steel buildings is presented. Furthermore, the proposed approach is used to explore the difference between the performance associated with these buildings by considering the three pillars of sustainability: economic, social, and environmental. Sustainability and resilience are both considered to cover a comprehensive performance‐based assessment content. The uncertainties associated with performance and consequence evaluation of structural and non‐structural components are incorporated within the assessment process. The proposed performance‐based assessment approach is illustrated on conventional and base‐isolated steel buildings under given seismic scenarios. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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Existing buildings can be at a greater seismic risk due to non-conformance to current design codes and may require structural retrofitting to improve building performance. The performance of buildings is measured in terms of immediate consequences due to direct damage, but the continuing impacts related to recovery are not considered in seismic retrofit assessment. This paper introduces a framework of retrofit selection based on the seismic resilience of deficient buildings retrofitted with the conventional mitigation approaches. The assembly-based methodology is considered for the seismic resilience assessment by compiling a nonlinear numerical model and a building performance model. The collapse fragility is developed from the capacity curve, and the resulting social, economic, and environmental consequences are determined. The seismic resilience of a building is assessed by developing a downtime assessment methodology incorporating sequence of repairs, impeding factors, and utility availability. Five functionality states are developed for the building functionality given investigated time interval, and a functionality curve for each retrofit is determined. It is concluded that seismic resilience can be used as a performance indicator to assess the continuing impacts of a hazard for the retrofit selection. 相似文献
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在侧向风力或侧向水平地源力作用下,斜拉桥容易发生扭转振动。本文采用非线性Rayleigh阴尼,它能反映在低速振动时有激发而加速振动,至一定高速后又衰减的完整振动过程。对非线性的统辖方程及定解条件,先使之无量纲化,再按非线性项的系数这个小参数展开未知函数,得到线性化的各级近似方程。把待求函数展成梁轴坐标的Fourier级数,其系数为待定的时间函数,应用Fourier级数的正交性,得到求解未知时间函数的二阶常微分方程,完全类似单自由度质点在线性粘滞性阻尼作用下的统辖方程,其解为已知。 相似文献
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现有的抗震避灾韧性评估模型存在着评估精准性差、模型灵活性差的缺陷,为了解决上述问题,提出标致性景观设计抗震避灾韧性评估模型分析与研究。通过对现有模型的分析,对构建的抗震避灾韧性评估模型整体架构进行提出,以此为基础构建整体结构数值分析模型,并采用回归分析方法对非线性动力时程进行分析,得到标致性景观抗震避灾韧性评估指标-损伤指数,采用pushover分析方法对损伤分布系数进行计算,以得到的损伤分布系数为依据建立标致性景观性易损性曲面,由其推导出抗震避灾韧性指数公式,从而实现标致性景观设计抗震避灾韧性的评估。通过实验得到,与现有的抗震避灾韧性评估模型相比较,构建的抗震避灾韧性评估模型极大的提升了评估的精准性与模型的灵活性,充分说明构建的标致性景观设计抗震避灾韧性评估模型具备更好的评估性能。 相似文献
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非线性地震道的混沌反演——Ⅱ.关于Lyapunov指数和吸引子 总被引:29,自引:4,他引:25
在本文上篇《非线性地震道的混沌反演--1.理论和数值试验》中讨论了非线性反问题逐次线性化方法及迭代过程的系统特性、递推法和广义线性反演法输出波阻抗序列的特征。本篇参照混沌理论中关于Lyapunov指数、相空间和吸引子的概念,深入研究逐次线性化迭代的状态变化的阶段性及其定量描述.当引用相空间描述系统的演化时,对于随迭代变化的阻尼因子可以发现几种吸引子.最后,总结了非线性地震混沌反演的要点,指出非线性反演迭代的复杂阶段性要川混沌理论来描述,而Lyapunov指数等才是控制迭代过程的实质性参数. 相似文献