共查询到18条相似文献，搜索用时 843 毫秒
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地震总输入能量与瞬时输入能量谱的研究 总被引：2，自引：0，他引：2
现有的抗震设计理论大多是基于承载力或强度的设计方法,与其相应的反应谱理论最大的缺陷是无法反映地震动持时的影响,而以地震动能量作为设计参数时就能弥补现有抗震理论的不足。本文按照反应谱理论的思路建立了线性单自由度体系的地震动总输入能量谱和瞬时输入能量谱。研究发现,阻尼比为5%时的地震动总输入能量谱和最大瞬时输入能量谱的等价速度谱可以分别用阻尼比为0.5%和10%下的拟速度谱来近似获得;地震波的V/A值大于0.15时,总输入能量谱的Δt谱峰值与地震波的强震持时呈线性增长关系,V/A值小于0.15时,两者间的关系无规律性。最大瞬时输入能量谱的Δt谱峰值基本不受地震波的V/A值与强震持时的影响;输入能量谱(总输入能量谱与最大瞬时输入能量谱)的特征周期随地震波V/A值的增大而增大,根据分析结果本文提出了线性单自由度体系输入能量谱的简化计算方法,方法简便,计算结果偏安全。 相似文献
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通过对多自由度体系结构在地震作用下的能量分析,考虑地震动因素和结构自身特性,提出一种框架结构地震总输入能量的简化求解方法.实例计算结果表明:基于等效单自由度体系来估计多自由度体系的地震总输入能,是一种计算简便且较为准确的方法. 相似文献
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双线性单自由度体系强迫动力反应的Hilbert谱与本征振动模态:输入简谐波频率的影响 总被引：5，自引：1，他引：4
系统地研究了双线性单自由度体系在简谐波输入下表现出非线性力学行为时,输入简谐波频率对体系动力响应的Hilbert谱、Hilbert边缘谱及Fourier幅值谱的影响.研究结果表明,如果体系输入简谐波频率为f,那么体系动力响应Hilbert边缘谱的能量分布在f附近一个较宽的频带上,该频带的产生是体系动力响应Hilbert谱中所蕴含的波内调制的必然结果,它源自于体系某个本征振动模态瞬时频率的波动,而这种瞬时频率的波动描述了体系屈服与卸载的非线性力学行为;体系动力响应的Fourier幅值谱自3f起,每隔2f就会出现一个幅值明显高出周围其它分量的Fourier“伪”谐波分量,这也是体系非线性力学行为所造成的结果. 相似文献
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本文将不同持续时间的八条天然地震记录及大量人工地震波,分别输入不同周期的11个个单自由度体系及三座遭受实际震害的多自由度结构中,进行直接动力积分计算,从计算出的累积变形能,能量反应指数和延性反应的结果中,分析它们与地震动持续时间的关系。其结果表明,我们所定义的能量指数对持续时间最为敏感。 相似文献
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基于瞬时输入能量的SDOF弹塑性结构最大位移反应分析 总被引：2，自引：0，他引：2
分析了不同周期的SDOF弹塑性模型在强震作用下的能量反应和位移反应，通过对二者相关性的探讨，提出了由瞬时输入能量推算结构最大位移反应的近似方法。 相似文献
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延性系数对SDOF体系地震能量输入历程的影响研究 总被引：4，自引：0，他引：4
文中以弹塑性SDOF体系为对象,提出将总输入能、最大瞬时输入能以及能量增长持时作为描述地震能量输入历程的三个特征参数。根据场地条件及地震动峰值速度与峰值加速度比值(V/A)双参数控制选择了不同场地条件下56条强震记录为输入,讨论延性系数的变化对这三个参数的影响。研究表明,随着延性系数的增加,总输入能量谱及最大瞬时输入能量谱在减小谱峰值的同时,谱型整体向短周期移动,形成压缩效应;弹塑性能量增长持时谱较弹性能量增长持时谱更为平滑,其谱值在统计意义上不发生变化;短周期结构延性的增大使得总输入能与最大瞬时输入能增加,但对于中长周期结构,总输入能与最大瞬时输入能随延性系数增加而减少;输入能量在时间轴上的分布模式受延性系数变化的影响不明显,能量时程增长台阶的总长度在各种延性系数条件下趋于一致。 相似文献
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This paper presents qualitative investigations on the energy behaviour of structures into which hysteretic dampers are incorporated. Emphasis was given to the ratio of the structural stiffness after the yielding of hysteretic dampers to the initial elastic stiffness, with a premise that this ratio, termed α in this study, tends to be large for structures with hysteretic dampers. Structures concerned were represented by discrete spring–mass systems having bilinear restoring force behaviour, in which the second stiffness relative to the initial stiffness is α. It was found that with the increase of α the total input energy tends to increase, but the increase is confined to a narrow range of natural periods. Both the total input energy and hysteretic energy were found to become less sensitive to the yield strength with the increase of α. A simple formula was also proposed to estimate the maximum deformation given the knowledge of the hysteretic energy. Analysis of MDOF systems revealed that, even when α is large, the total input energy and hysteretic energy for MDOF systems are approximately the same as those of the equivalent SDOF system, and the hysteretic energy can be distributed uniformly over the stories if α is large. 相似文献
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A new critical excitation method is developed for soil–structure interaction systems. In contrast to previous studies considering amplitude nonstationarity only, no special constraint of input motions is needed on nonstationarity. The input energy to the soil–structure interaction system during an earthquake is introduced as a new measure of criticality. It is demonstrated that the input energy expression can be of a compact form via the frequency integration of the product between the input component (Fourier amplitude spectrum) and the structural model component (so-called energy transfer function). With the help of this compact form, it is shown that the formulation of earthquake input energy in the frequency domain is essential for solving the critical excitation problem and deriving a bound on the earthquake input energy for a class of ground motions. The extension of the concept to MDOF systems is also presented. 相似文献
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基于MPA方法的结构滞回耗能计算 总被引：2，自引：0，他引：2
在能量反应分析中,滞回耗能是最具明确工程意义的而又便于工程应用的能量指标,可用以衡量结构的塑性累积损伤。然而,以往研究中,在计算多自由度体系的滞回耗能时,通常采用时程分析法,计算比较烦杂,不利于工程实际的应用。因此,本文提出了一种采用模态pushover分析（MPA）计算多层结构滞回耗能的简便方法,并通过两个高层结构算例,验证了该方法的精度。结果表明：基于模态pushover分析的结构滞回耗能计算方法精度良好,结果可靠;对于框架结构,可以直接采用第一阶模态（倒三角）加载模式对结构进行pushover分析计算,对于高层框架剪力墙结构,必须组合高阶模态的滞回耗能计算结果。 相似文献
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Hysteretic energy dissipation in a structure during an earthquake is the key factor, besides maximum displacement, related to the amount of damage in it. This energy demand can be accurately computed only through a nonlinear time‐history analysis of the structure subjected to a specific earthquake ground acceleration. However, for multi‐story structures, which are usually modeled as multi‐degree of freedom (MDOF) systems, this analysis becomes computation intensive and time consuming and is not suitable for adopting in seismic design guidelines. An alternative method of estimating hysteretic energy demand on MDOF systems is presented here. The proposed method uses multiple ‘generalized’ or ‘equivalent’ single degree of freedom (ESDOF) systems to estimate hysteretic energy demand on an MDOF system within the context of a ‘modal pushover analysis’. This is a modified version of a previous procedure using a single ESDOF system. Efficiency of the proposed procedure is tested by comparing energy demands based on this method with results from nonlinear dynamic analyses of MDOF systems, as well as estimates based on the previous method, for several ground motion scenarios. Three steel moment frame structures, of 3‐, 9‐, and 20‐story configurations, are selected for this comparison. Bias statistics that show the effectiveness of the proposed method are presented. In addition to being less demanding on the computation time and complexity, the proposed method is also suitable for adopting in design guidelines, as it can use response spectra for hysteretic energy demand estimation. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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A modified energy-balance equation accounting for P-delta effects and hysteretic behavior of reinforced concrete members is derived. Reduced hysteretic properties of structural components due to combined stiffness and strength degradation and pinching effects, and hysteretic damping are taken into account in a simple manner by utilizing plastic energy and seismic input energy modification factors. Having a pre-selected yield mechanism, energy balance of structure in inelastic range is considered. P-delta effects are included in derived equation by adding the external work of gravity loads to the work of equivalent inertia forces and equating the total external work to the modified plastic energy. Earthquake energy input to multi degree of freedom (MDOF) system is approximated by using the modal energy-decomposition. Energy-based base shear coefficients are verified by means of both pushover analysis and nonlinear time history (NLTH) analysis of several RC frames having different number of stories. NLTH analyses of frames are performed by using the time histories of ten scaled ground motions compatible with elastic design acceleration spectrum and fulfilling duration/amplitude related requirements of Turkish Seismic Design Code. The observed correlation between energy-based base shear force coefficients and the average base shear force coefficients of NLTH analyses provides a reasonable confidence in estimation of nonlinear base shear force capacity of frames by using the derived equation. 相似文献
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A procedure is proposed whereby input and hysteretic energy spectra developed for single-degree-of-freedom (SDOF) systems are applied to multi-degree-of-freedom (MDOF) steel moment resisting frames. The proposed procedure is verified using four frames, viz., frame with three-, five-, seven- and nine-stories, each of which is subjected to the fault-normal and fault-parallel components of three actual earthquakes. A very good estimate for the three- and five-story frames, and a reasonably acceptable estimate for the seven-, and nine-story frames, have been obtained. A method for distributing the hysteretic energy over the frame height is also proposed. This distribution scheme allows for the determination of the energy demand component of a proposed energy-based seismic design (EBSD) procedure for each story. To address the capacity component of EBSD, a story-wise optimization design procedure is developed by utilizing the energy dissipating capacity from plastic hinge formation/rotation for these moment frames. The proposed EBSD procedure is demonstrated in the design of a three-story one-bay steel moment frame. 相似文献
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基于小波变换的结构地震响应与能量计算分析 总被引：1，自引：0，他引：1
多分辨分析可将地震信号分解到不同的频段。本文推导了运用多分辨分析计算多自由度体系地震响应的基本公式,讨论了各频段地震信号及结构响应的能量分配。最后,通过多自由度体系的算例验证了弹性体系在原始地震作用下的动力响应可以由该地震作用在时域的各小波分量的动力响应叠加而得,同时将高频抑制后的重构信号应用于近似模型的计算,并利用能量分析明确了地震信号与结构响应在各频段的能量分配。 相似文献