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本文利用非线性理论分析了震前形变能随时间的演化关系，导出了应力与应变的本构关系为非线性时的突变演化模型。最后利用青海门源６．４级地震前后的跨断层形变资料，计算了非线性形变的演化过程。取得如下认识：１．震前形变能的演化过程是不稳定过程；２．形变能的突变发生在非平衡区；３．门源地震前后的跨断层地形变资料的计算结果与理论分析基本一致。 相似文献
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渡槽中流体非线性晃动的边界元模拟 总被引：20，自引：0，他引：20
应用边界元法分析了流体非线性晃动及其对渡槽的作用效应,将所得结果与线性解析结果作了比较．数值计算表明：流体以较大幅度晃动时,线性模型结果与非线性边界元结果有较大偏差,计算有限幅流体晃动反应宜采用非线性模型． 相似文献
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钢筋混凝土开洞剪力墙结构抗震非线性有限元分析 总被引：6，自引：1，他引：6
本文以钢筋混凝土开洞剪力墙结构为研究对象，建立了该类结构动力非线性有限元分析计算及该类结构静力非线性pushover有限元分析计算的基本过程，并编制了相应的计算机程序．通过与实验分析结果的比较，检验了本文动力非线性有限元分析计算方法的准确程度，验证了静力非线性pushover有限元分析方法应用于开洞剪力墙抗震非线性性能评估的可靠性。 相似文献
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本文分别采用纤维单元模型和塑性铰单元模型对一个四层足尺钢框架振动台试验进行模拟分析,在三维空间非线性分析程序Perform-3D中进行动力非线性分析,比较分析结果,并与试验结果对比,以研究两种模型应用于钢框架整体结构非线性分析的计算精度。文中并讨论了纤维单元模型截面纤维的划分、塑性区长度的取值等问题。最后对采用组合梁的整体结构模型进行了动力非线性分析。结果表明,纤维模型的建模速度比塑性铰模型快,但塑性铰模型能模拟结构的倒塌时间。Perform-3D程序的纤维单元模型和塑性铰单元模型用于计算我国规范规定的7度和8度地震作用的多层钢框架结构,其结果是真实可靠的,而且计算结果偏于安全。 相似文献
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有横缝拱坝的非线性动力模型试验和计算分析研究 总被引：12，自引：0，他引：12
本文通过在大型三向地震模拟振动台上进行的设置伸缩横缝的某拱坝非线性动力模型试验，应用非线性有限元动力分析程序同时进行计算分析，全面系统地研究了拱坝横缝对坝体动力特性和地震反应的影响，并对计算程序进行了改进。试验与计算结果相互印证，验证了试验成果的可靠性和计算分析模型、计算程序与计算结果的合理性。 相似文献
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钢筋混凝土核心筒体抗震性能分析 总被引：3，自引：1，他引：3
本文在非线性有限元计算模型和分析程序的基础上，对影响钢筋混凝土核心筒体抗震性能的三个重要参数，即高宽比、轴压比、连梁刚度比，进行了一系列模型的非线性计算分析，得出了各参数对核心筒的承载力、破坏形式、延性、耗能能力等抗震性能的影响，为参数影响的定量研究和工程设计提供了有价值的参考。 相似文献
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合理有效的工程场地自由场分析是开展地下结构地震反应计算、发展地下结构实用抗震分析方法的前提。目前常用的自由场分析方法多局限于单向地震动输入，难以考虑多向地震动共同作用时的非线性耦合效应。鉴于此，提出一种考虑水平和竖向地震动及重力荷载共同作用的土层地震反应分析力学模型，该模型采用捆绑约束条件作为侧面边界条件，采用基于黏性边界的地震动输入方法将输入地震动转化为等效地震荷载，可实现自由场计算中水平和竖向地震动以及重力荷载的同时施加，简化了计算步骤，减少了计算成本。此外，该方法考虑了水平和竖向地震荷载的叠加效应，对于考虑材料非线性及大变形影响的土层场地地震反应分析具有更为良好的计算精度与适用性。 相似文献
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通过观察和模拟干扰源试验,认为红山地震台ＧＳ－１５型重力仪潮汐观测曲线畸变和观测精度氏是因原配ＲＣ滤波电路的抗干扰能力差。用自制的有源贝赛尔滤波电路取代原配ＲＣ滤波电路后,观测质量得到了根本的改善,一系列参量的分析表明,ＧＳ型重力仪弹性系统手换能电路性能优良,有源滤波电路具有很强的抗干扰能力,使用数字记录代替模拟记录可以减小记录系统非线性失真,提高潮汐分析的精度和稳定性。 相似文献
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滞变—摩擦基底隔震支座的试验和模型 总被引：5，自引：3，他引：5
本提出了一种滞变－摩擦基底隔震支座。这种支座由钢棒和摩擦元件组成，钢棒容许摩擦元件水平滑动，同时又限制这种滑动；摩擦元件承受结构的竖向荷载，作完成了钢棒滞变恢复力特性的试验，并给出了钢棒的滞变恢复力模型的模型参数的计算公式，该模型与常用的折线模型有所不同，它仅用一个非线性微分方程来描述滞变恢复力，而不需要复杂的规则。 相似文献
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Based on a framework of Probabilistic Seismic Demand Analysis, a nonlinear dynamic model of a reinforced concrete (RC) building was established to obtain a demand hazard curve that considers multidimensional performance limit states (MPLSs), including combinations of peak floor acceleration and interstory drift. A definition of the two limit states is expressed using a generalized MPLSs equation. The peak floor acceleration and the interstory drift were considered to be dependent and were assumed to follow a bidimensional lognormal distribution. The maximum interstory drift and the maximum peak floor acceleration were calculated using Increment Dynamic Analysis and nonlinear time history analysis. The numerical formula for a demand hazard curve of the modelled building was then derived by coupling the bidimensional lognormal distribution with the ground motion hazard curve. The uncertainties involved in MPLSs and structural parameters, as well as the different threshold values for peak floor acceleration, were further considered to determine the sensitivity of demand hazard curves. The analysis results showed that the proposed method can be used to describe the damage performance of various building structures, which are sensitive to multiple response parameters including drift and acceleration. Moreover, it was demonstrated in this study that the demand hazard curves were relatively conservative if the coefficient of variation, the peak floor acceleration threshold, the interaction factor N IDR and added stiffness, were appropriately selected. 相似文献
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This work proposes two modelling frameworks for diagnosing temporal variations in nonlinear rating curves that describe suspended sediment–discharge relationships. A variant of the weighted regression on time, discharge, and season model is proposed and is compared against dynamic nonlinear modelling, a newly developed nonlinear time series filter based on sequential Monte Carlo sampling. Both approaches estimate a time series of rating curve parameters, with uncertainty, that can be used to diagnose variability in the sediment–discharge relationship over time. We evaluate the models with a variety of synthetic scenarios to highlight their ability to estimate signals of known rating curve change. Results reveal important bias‐variance trade‐offs unique to each approach, and in general, suggest that dynamic nonlinear modelling is better suited for rapid rating curve changes, whereas the weighted regression on time, discharge, and season variant more precisely estimates slow change. The techniques are then applied in two case studies in the Upper Hudson and Mohawk Rivers in New York. We conclude with a discussion of the implications of dynamic rating curves for the management of water quality in riverine and estuary systems. 相似文献
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《Advances in water resources》1998,22(4):399-412
Linear instability and nonlinear energy stability analyses are developed for the problem of a fluid-saturated porous layer stratified by penetrative thermal convection and two salt concentrations. Unusual neutral curves are obtained, in particular non-perfect `heart-shaped' oscillatory curves that are disconnected from the stationary neutral curve. These curves show that three critical values of the thermal Rayleigh number may be required to fully describe the linear stability criteria. As the penetrative effect is increased, the oscillatory curves depart more and more from a perfect heart shape. For certain values of the parameters it is shown that the minima on the oscillatory and stationary curves occur at the same Rayleigh number but different wavenumbers, offering the prospect of different types of instability occurring simultaneously at different wavenumbers. A weighted energy method is used to investigate the nonlinear stability of the problem and yields unconditional results guaranteeing nonlinear stability for initial perturbations of arbitrary sized amplitude. 相似文献
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Nonstationary stochastic response of structural systems equipped with nonlinear viscous dampers under seismic excitation 总被引：1，自引：0，他引：1 
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下载免费PDF全文 Nonlinear viscous dampers are supplemental devices widely used for enhancing the performance of structural systems exposed to seismic hazard. A rigorous evaluation of the effect of these damping devices on the seismic performance of a structural system should be based on a probabilistic approach and take into account the evolutionary characteristics of the earthquake input and of the corresponding system response. In this paper, an approximate analytical technique is proposed for studying the nonstationary stochastic response characteristics of hysteretic single degree of freedom systems equipped with viscous dampers subjected to a fully nonstationary random process representing the seismic input. In this regard, a stochastic averaging/linearization technique is utilized to cast the original nonlinear stochastic differential equation of motion into a simple first‐order nonlinear ordinary differential equation for the nonstationary system response variance. In comparison with standard linearization schemes, the herein proposed technique has the significant advantage that it allows to handle realistic seismic excitations with time‐varying frequency content. Further, it allows deriving a formula for determining the nonlinear system response evolutionary power spectrum. By this way, ‘moving resonance’ effects, related to both the evolutionary seismic excitation and the nonlinear system behavior, can be observed and quantified. Several applications involving various system and input properties are included. Furthermore, various response parameters of interest for the seismic performance assessment are considered as well. Comparisons with pertinent Monte Carlo simulations demonstrate the reliability of the proposed technique. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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船艏正撞刚性墙力—撞深关系的简化公式研究 总被引：2，自引：0，他引：2
面向工程应用,基于船艏正撞刚性墙的有限元碰撞计算,提出了撞击力—船艏撞深关系的基本简化公式,以应用于船撞桥的质量-弹簧体系简化动力分析模型的有限元计算。使用LS-DYNA软件,通过3000~50000 DWT（dead weight tonnage,载重吨）范围内4艘典型船舶的有限元碰撞分析,得到了船舶在1.0~5.0 m/s冲击速度范围内,与刚性墙面正撞的撞击力—撞深样本曲线。根据对样本曲线的观察,提出了一种基本的撞击力—撞深关系的简化数学公式,并统计得到了公式中各参数的表达式。船桥碰撞实际工况的有限元计算对比表明,提出的简化公式可以满足船桥碰撞简化动力分析的需要。 相似文献
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GS-15型重力仪是利用摆杆位移大小来量度重力相对变化的精密仪器,摆杆位移是通过电容换能进行测量。由于该仪器为开环检测系统,而且系统的末级加接0.01Hz的有源滤波器,这样就失去了大于0.01Hz的高频成分,且使潮波产生相位失真,同时还存在着电路非线性带来的测量误差,因而测量精度难以提高。为此笔者对GS-15型重力仪加装了电磁反馈装置,将开环检测改为闭环检测,利用电磁力使重力仪摆杆始终处于零电平的动态平衡状态,以电磁反馈输出大小来度量重力的变化,这样就将开环检测系统改装为平衡电桥闭环检测系统,其时间常数为2秒。 改装后,消除了电路的非线性影响,增强了系统的稳定性,记录的固体潮含有丰富的谐波,同时系统还增加了一路稳态零位输出,为地壳形变、地震预报和地球物理研究提供了波群丰富的资料 相似文献