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1.
Gaussian mixture–based equivalent linearization method (GM-ELM) is a recently developed stochastic dynamic analysis approach which approximates the random response of a nonlinear structure by collective responses of equivalent linear oscillators. The Gaussian mixture model is employed to achieve an equivalence in terms of the probability density function (PDF) through the superposition of the response PDFs of the equivalent linear system. This new concept of linearization helps achieve a high level of estimation accuracy for nonlinear responses, but has revealed some limitations: (1) dependency of the equivalent linear systems on ground motion intensity and (2) requirements for stationary condition. To overcome these technical challenges and promote applications of GM-ELM to earthquake engineering practice, an efficient GM-ELM-based fragility analysis method is proposed for nonstationary excitations. To this end, this paper develops the concept of universal equivalent linear system that can estimate the stochastic responses for a range of seismic intensities through an intensity-augmented version of GM-ELM. Moreover, the GM-ELM framework is extended to identify equivalent linear oscillators that could capture the temporal average behavior of nonstationary responses. The proposed extensions generalize expressions and philosophies of the existing response combination formulations of GM-ELM to facilitate efficient fragility analysis for nonstationary excitations. The proposed methods are demonstrated by numerical examples using realistic ground motions, including design code–conforming nonstationary ground motions. 相似文献
2.
A stochastic approach for obtaining reliable estimates of the peak response of nonlinear systems to excitations specified via a design seismic spectrum is proposed. This is achieved in an efficient manner without resorting to numerical integration of the governing nonlinear equations of motion. First, a numerical scheme is utilized to derive a power spectrum which is compatible in a stochastic sense with a given design spectrum. This power spectrum is then treated as the excitation spectrum to determine effective damping and stiffness coefficients corresponding to an equivalent linear system (ELS) via a statistical linearization scheme. Further, the obtained coefficients are used in conjunction with the (linear) design spectrum to estimate the peak response of the original nonlinear systems. The cases of systems with piecewise linear stiffness nonlinearity, along with bilinear hysteretic systems are considered. The seismic severity is specified by the elastic design spectrum prescribed by the European aseismic code provisions (EC8). Monte Carlo simulations pertaining to an ensemble of nonstationary EC8 design spectrum compatible accelerograms are conducted to confirm that the average peak response of the nonlinear systems compare reasonably well with that of the ELS, within the known level of accuracy furnished by the statistical linearization method. In this manner, the proposed approach yields ELS which can replace the original nonlinear systems in carrying out computationally efficient analyses in the initial stages of the aseismic design of structures under severe seismic excitations specified in terms of a design spectrum. 相似文献
3.
Track nonlinear energy sinks (track NESs) have been shown to be an effective and applicable strategy to mitigate structural response in recent years. However, previous studies on track NESs has mainly focused on demonstrating the benefits of track NESs through numerical simulations and experiments, with relatively little attention paid to the analytical understanding of the unique dynamics of track NESs. This study analyzes the responses of a track NES when subjected to impulsive and harmonic excitations by the harmonic balance method. Special attention is given to the cause and effect of the peaking behavior that is a prominent characteristic of the track NES's restoring force–displacement relationship. Analytical results reveal that the special energy–frequency characteristics of track NESs can be, at times, utilized to enhance the energy robustness that is absent in the conventional cubic NESs. Based on the analytical response expression, an equivalent linearization method (ELM) for the track NESs is developed for stochastic analysis. This ELM is numerically validated on the systems with strong nonlinearities. Stochastic optimization built on the ELM is performed to obtain design parameters of the track NES that can lead to minimum response variances of the primary structure. In particular, the proposed optimization procedure can be applied to seismic optimum design in which the seismic excitations are modeled as filtered white-noise ground motions. The analytical techniques provided in this study lay the groundwork for the practical implementation of track NESs as a robust and effective control strategy for engineering structures. 相似文献
4.
This paper concerns the seismic response of structures isolated at the base by means of High Damping Rubber Bearings (HDRB). The analysis is performed by using a stochastic approach, and a Gaussian zero mean filtered non‐stationary stochastic process is used in order to model the seismic acceleration acting at the base of the structure. More precisely, the generalized Kanai–Tajimi model is adopted to describe the non‐stationary amplitude and frequency characteristics of the seismic motion. The hysteretic differential Bouc–Wen model (BWM) is adopted in order to take into account the non‐linear constitutive behaviour both of the base isolation device and of the structure. Moreover, the stochastic linearization method in the time domain is adopted to estimate the statistical moments of the non‐linear system response in the state space. The non‐linear differential equation of the response covariance matrix is then solved by using an iterative procedure which updates the coefficients of the equivalent linear system at each step and searches for the solution of the response covariance matrix equation. After the system response variance is estimated, a sensitivity analysis is carried out. The final aim of the research is to assess the real capacity of base isolation devices in order to protect the structures from seismic actions, by avoiding a non‐linear response, with associated large plastic displacements and, therefore, by limiting related damage phenomena in structural and non‐structural elements. In order to attain this objective the stochastic response of a non‐linear n‐dof shear‐type base‐isolated building is analysed; the constitutive law both of the structure and of the base devices is described, as previously reported, by adopting the BWM and by using appropriate parameters for this model, able to suitably characterize an ordinary building and the base isolators considered in the study. The protection level offered to the structure by the base isolators is then assessed by evaluating the reduction both of the displacement response and the hysteretic dissipated energy. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
5.
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
6.
This study evaluates the response reduction effect of linear single degree of freedom systems with a clutching inerter damper (CID) via parametric analysis under harmonic excitations and real earthquake records. The cause of the displacement reduction effect of a CID is inherited from the inertial mass damper (IMD)—reducing the nominal load intensity by increasing the mass by inertance. Additionally, the displacement reduction effect is further enhanced by the clutching effect, which speeds up the decreasing of the velocity response from an instantaneous extremum to 0. Thus, the CID is more effective than the IMD at reducing displacement responses. For example, the displacement response for a long‐period structure with a CID can be reduced by approximately 53%, while for an IMD, it can only be reduced by approximately 24%. Additionally, the linear single degree of freedom system with a CID is a weak nonlinear system reserving homogeneity, indicating that the response reduction factor will provide enough information to reveal the seismic reduction effect of the CID and that there is no need to consider the amplitude of the input excitations. To simplify the analysis of such nonlinear systems, an equivalent linearization method and a simplified formula of displacement reduction factors for code‐based designs are proposed and validated by another independent set of records from the European Strong‐motion Database. 相似文献
7.
将土非线性分析的等效线性化方法与随机工程波动散射问题的求解方法相结合，建立了开放系统中非一致激励条件下考虑岩土介质非线性的工程场地地震动随机场数值模拟方法并研究了介质非线性对场地地震动相干性的影响。分析结果表明：与不考虑非线性相比，在地震过程中，场地土介质的非线性改变了复杂场地的局部特性从而导致场地地震动空间相干性的变化，因此有必要在场地地震动相干函数的分析中考虑场地介质非线性特性对地震动相干性的影响。 相似文献
8.
对一维剪切条计算模型进行改进,提出了土石坝非线性地震反应的简化计算方法。首先将坝体沿坝高离散为一系列的具有不同剪切刚度与阻尼比等参数特性的层状体系,建立了各层的振动控制方程及其边值条件,进而采用数学物理方程方法进行了求解,确定了体系的振动特性,并根据振型叠加原理和Duhamel积分确定了坝体地震反应的线弹性解。采用等价线性化方法考虑坝料的动力非线性性质,通过对线弹性地震响应的反复迭代计算,使得各层土的模量和阻尼比与其相应的剪应变水平相协调,确定出与非线性坝体系统相等效的线性解答,并将所得到的地震响应作为非线性地震响应的近似解。最后,以均质坝和心墙坝作为算例进行了具体的数值计算,将所得结果与有限元数值解进行对比分析,论证了所提方法的适用性和合理性。 相似文献
9.
The equivalent linearization method approximates the maximum displacement response of nonlinear structures through the corresponding equivalent linear system.By using the particle swarm optimization technique,a new statistical approach is developed to determine the key parameters of such an equivalent linear system over a 2D space of period and damping ratio.The new optimization criterion realizes the consideration of the structural safety margin in the equivalent linearization method when applied to the performance-based seismic design/evaluation of engineering structures.As an application,equations for equivalent system parameters of both bilinear hysteretic and stiffness degrading single-degree-offreedom systems are deduced with the assumption of a constant ductility ratio.Error analyses are also performed to validate the proposed approach. 相似文献
10.
等效线性化方法是计算结构弹塑性地震反应的实用方法.通过对几种等效线性化方法的比较分析,提出了基于FEMA440 （2005）计算等效刚度和等效阻尼比的等效线性化方法;分别采用静力弹塑性分析方法和等效线性化方法,分析了局部使用高性能纤维增强混凝土新型框架结构的弹塑性地震反应.结果表明,两种方法所得结构的地震反应均比较接近.因此,本文建议的等效线性化方法能够较好地预测新型框架结构的弹塑性地震反应. 相似文献
11.
12.
城市桥梁粘滞阻尼器防地震碰撞分析与参数设计 总被引：2，自引：0，他引：2
研究了粘滞阻尼器防止城市梁桥地震碰撞反应的效果并提出了其参数设计方法。分析了线性粘滞阻尼器与非线性粘滞阻尼器阻尼系数的等效关系。运用随机振动理论与随机等效线性化理论建立了邻联间安装粘滞阻尼器后最大相对位移及墩顶最大位移的计算方法。以控制邻联最大相对位移小于实际间隙为目标,提出了防碰撞粘滞阻尼器参数设计方法。对1座4跨隔震连续梁桥进行了仿真分析,结果表明:粘滞阻尼器能有效抑制邻联的碰撞反应且不会显著增大桥墩的延性需求。在相同阻尼系数的情况下,粘滞阻尼器的速度指数越小,其防碰撞效果越好。利用人工波进行的时程分析结果验证了参数设计方法的可行性。 相似文献
13.
In the most recent seismic codes, the assessment of the seismic response of structures may be carried out by comparing the displacement capacity, provided by nonlinear static analysis, with the displacement demand. In many cases the code approach is based on the N2 method proposed by Fajfar, which evaluates the displacement demand by defining, as an intermediate step, a single degree‐of‐freedom (SDOF) system equivalent to the examined structure. Other codes suggest simpler approaches, which do not require equivalent SDOF systems, but they give slightly different estimation of the seismic displacement demand. The paper points out the differences between the methods and suggests an operative approach that provides the same accuracy as the N2 method without requiring the evaluation of an equivalent SDOF system. A wide parametric investigation allows an accurate comparison of the different methods and demonstrates the effectiveness of the proposed operative approach. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
14.
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
15.
随着地下空间大规模开发利用,地震灾害对其造成的潜在威胁不容忽视。基于《城市轨道交通结构抗震设计规范(GB50909-2014)》和《地下铁道建筑结构抗震设计规范(DG/TJ08-2064-2009)》建议的分析方法,选取惯性力法、反应位移法(国家规范法、上海规范法)、动力时程方法(线弹性方法、等效线性化方法)三类共5种计算方法,以典型两层双柱三跨地铁车站结构为分析对象进行地震反应的对比验算,对上述计算方法的适应性进行评价。分析结果表明,与动力时程方法相比较,惯性力法计算得到的侧墙剪力值偏大,中柱结果较为接近;对于反应位移法,国家规范方法和上海规范方法的计算模型略有不同,但两者计算结果基本相近,其中土体强制位移、集中地基弹簧、土体动剪切模量等参数取值对计算结果影响显著;对于动力时程方法,线弹性方法和等效线性化方法的结果较为接近,且变化趋势相同。 相似文献
16.
通过有限元方法进行非线性动力时程分析获取解析的易损性曲线,计算量大且耗时。本文采用一种简化的计算方法,即基于单自由度的等效线性化模型,对钢筋混凝土框架结构进行地震易损性分析,并研究了该方法在结构高度上的适用性。通过选用5种典型的等效线性化模型对3栋不同高度的钢筋混凝土框架结构进行增量动力分析（IDA）,得到了不同高度的结构在不同强度地震作用下结构的反应和易损性,并与OpenSees程序的计算结果进行对比,研究了等效线性化模型应用于RC框架结构易损性分析在高度上的适用性。分析结果表明:对于10层及以下的框架结构,基于单自由度的等效线性化模型在结构地震易损性分析中具有较好的适用性;对于更高层数的结构,由于高阶振型反应对整体结构反应的影响增大,基于单自由度等效线性化模型的易损性分析结果会出现明显的偏差。 相似文献
17.
The seismic performance of existing structures can be assessed based on nonlinear static procedures, such as the Capacity Spectrum Method. This method essentially approximates peak responses of an inelastic single‐degree‐of‐freedom (SDOF) system using peak responses of an equivalent linear SDOF model. In this study, the equivalent linear models of inelastic SDOF systems are developed based on the constant strength approach, which does not require iteration for assessing the seismic performance of existing structures. To investigate the effects of earthquake type and seismic region on the equivalent linear models, four ground‐motion data sets—Japanese crustal/interface/inslab records and California crustal records—are compiled and used for nonlinear dynamic analysis. The analysis results indicate that: (1) the optimal equivalent linear model parameters (i.e. equivalent vibration period ratio and damping ratio) decrease with the natural vibration period, whereas they increase with the strength reduction factor; (2) the impacts of earthquake type and seismic region on the equivalent linear model parameters are not significant except for short vibration periods; and (3) the degradation and pinching effects affect the equivalent linear model parameters. We develop prediction equations for the optimal equivalent linear model parameters based on nonlinear least‐squares fitting, which improve and extend the current nonlinear static procedure for existing structures with degradation and pinching behavior. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
18.
Procedures for calibration of linear models for damage limitation in design of masonry‐infilled RC frames 下载免费PDF全文
下载免费PDF全文 Paolo Ricci Maria Teresa De Risi Gerardo Mario Verderame Gaetano Manfredi 《地震工程与结构动力学》2016,45(8):1315-1335
Recent earthquakes have confirmed the role played by infills in the seismic response of reinforced concrete buildings. The control and limitation of damage to such nonstructural elements is a key issue in performance‐based earthquake engineering. The present work is focused on modeling and analysis of damage to infill panels, and, in particular, it is aimed towards linear analysis procedures for assessing the damage limitation limit state of infilled reinforced concrete frames. First, code provisions on infill modeling and acceptance criteria at the damage limitation limit state are reviewed. Literature contributions on damage to unreinforced masonry infill panels and corresponding displacement capacity are reported and discussed. Two procedures are then proposed aiming at a twofold goal: (i) the determination of ‘equivalent’ interstory drift ratio limits for a bare frame model and (ii) the estimation of the stiffness of equivalent struts representing infill walls in a linear model. These two quantities are determined such that a linear model ensures a reliable estimation of seismic capacity at the damage limitation limit state, providing the same intensity level as that obtained from nonlinear analyses carried out on structural models with infills. Finally, the proposed procedures are applied to four‐story and eight‐story case study‐infilled frames, designed for seismic loads according to current technical codes. The results of these application examples are presented and discussed. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
19.
粘弹性阻尼器连接的相邻结构非线性随机地震反应分析 总被引：7，自引：1，他引：7
本文用随机等价线性化方法探讨了相邻结构之间用粘弹性阻尼器连接后的非线性随机地震反应，分析发现：在小震作用下，粘弹性阻尼器对相邻结构可以同时达到较好的控制效果；但是在强烈地震作用下，安装粘弹性阻尼器有可能会在减少一个结构的地震反应的同时，增大另外一个结构的地震反应。 相似文献
20.
The present study deals with the non‐linear stochastic dynamic analysis of a soil–structure interacting system. The ultimate objective is to determine the risk of damage to the system due to liquefaction under a wide range of earthquake intensities. A Monte Carlo simulation approach is followed in conjunction with advanced finite element procedures. The stochastic spatial variability of soil properties and the randomness of the seismic excitation are taken into account in order to estimate the statistics of the response, measured in terms of uniform foundation settlement and tilting. Specifically, soil properties are modelled as non‐Gaussian random fields and seismic excitations as non‐stationary random processes. The probabilistic characteristics of the stochastic field modelling soil properties are established from in situ tests. The risk of damage to the soil–structure system due to liquefaction is assessed by establishing fragility curves, which are of paramount importance for risk assessment and management studies of such systems. Fragility curves express the probability of exceeding various thresholds in the response. The relative effect of the variability of various soil parameters on the variability of the response is also examined. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献