共查询到20条相似文献，搜索用时 6 毫秒
1.
A general procedure is presented to study the dynamic soil–structure interaction effects on the response of long-span suspension and cable-stayed bridges subjected to spatially varying ground motion at the supporting foundations. The foundation system is represented by multiple embedded cassion foundations and the frequency-dependent impedance matrix for the multiple foundations system takes into account also the cross-interaction among adjacent foundations through the soil. To illustrate the potential implementation of the analysis, a numerical example is presented in which the dynamic response of the Vincent–Thomas suspension bridge (Los Angeles, CA) subjected to the 1987 Whittier earthquake is investigated. Although both kinematic and inertial effects are included in the general procedure, only the kinematic effects of the soil–structure interaction are considered in the analysis of the test case. The results show the importance of the kinematic soil–foundation interaction on the structural response. These effects are related to the type, i.e. SH-, SV-, P- or Rayleigh waves and to the inclination of the seismic wave excitation. Moreover, rocking components of the foundation motion are emphasized by the embedment of the foundation system and greatly alter the structural response. 相似文献
2.
Reduction of structural response to near fault earthquakes by seismic isolation columns and variable friction dampers 总被引：2，自引：2，他引：0
Y. Ribakov 《地震工程与工程振动(英文版)》2010,9(1):113-122
<正>This paper focuses on the investigation of a hybrid seismic isolation system with passive variable friction dampers for protection of structures against near fault earthquakes.The seismic isolation can be implemented by replacing the conventional columns fixed to the foundations by seismic isolating ones.These columns allow horizontal displacement between the superstructure and the foundations and decouple the building from the damaging earthquake motion.As a result, the forces in the structural elements decrease and damage that may be caused to the building by the earthquake significantly decreases.However,this positive effect is achieved on account of displacements occurring in the isolating columns.These displacements become very large when the structure is subjected to a strong earthquake.In this case,impact may occur between the parts of the isolating column yielding their damage or collapse.In order to limit the displacements in the isolating columns,it is proposed to add variable friction dampers.A method for selecting the dampers' properties is proposed.It is carried out using an artificial ground motion record and optimal active control algorithm.Numerical simulation of a seven-story structure shows that the proposed method allows efficient reduction in structural response and limits the displacements at the seismic isolating columns. 相似文献
3.
This paper deals with the vibration control of existing structures forced by earthquake induced ground motion. To this aim it is proposed for the first time to exploit the structure–soil–structure mechanism to develop a device, hosted in the soil but detached from the structure, able to absorb part of the seismic energy so to reduce the vibration of neighbourhood structures. The design of the device is herein addressed to protect monopile structures from earthquake induced ground motion. By modelling the ground motion as zero-mean quasi-stationary response-spectrum-compatible Gaussian stochastic process, the soil as visco-elastic medium and the target monopiled-structure as a linear behaving structure the device, herein called Vibrating Barrier (ViBa), has been designed through an optimization procedure. Various numerical and experimental results are produced to show the effectiveness of the ViBa. Remarkably, a significant reduction of the structural response up to 44% has been achieved. 相似文献
4.
An important aspect of earthquake loads exerted on extended structures, or structures founded on several foundations, is the spatial variability of the seismic motion. Hence, a rigorous earthquake resistant design of lifeline structures should account for the spatial character of the seismic input, at least in an approximate way. A procedure is proposed which enables addressing the problem of multiply supported structures, subjected to imperfectly correlated seismic excitations, by means of an extension to the response spectrum method. A modified response spectrum model is developed for the design of extended facilities subjected to single and multicomponent ground motion. The modification procedure is based on adjusting each spectral value of the given design response spectrum by means of a correction factor, which depends on the structural properties and on the characteristics of the wave propagation phenomenon. Finally, the theoretical model is validated through digital simulation of seismic ground motion, whereby model predictions are found to be in good agreement with exact results. 相似文献
5.
The seismic analysis of structures is usually carried out considering the ground motion as fully‐correlated in space and determining the structural response by pseudo‐deterministic methods such as the response spectrum technique. Actually, the partial correlation of the seismic acceleration may influence heavily the behaviour of spatially extended structures, such as bridges, viaducts or pipelines. In order to take its partial correlation into account, the seismic ground motion is schematized as a stochastic process dependent on time and on space; the hypotheses of stationarity and homogeneity are used to obtain simple and general results. The influence of the partial correlation of the seismic ground motion on the structural response is investigated by introducing suitable Equivalent Spectra. The acceleration of the support‐points of the structure is represented by the Proper Orthogonal Decomposition (POD), defining the modes of the earthquake. The method is formulated for any kind of multi‐degree‐of‐freedom system and is applied, as a case study, to an ideal single‐storey multi‐supported frame with an axially rigid beam. In the case of two supports, the POD decouples the pseudo‐static and the dynamic contributions to the structural response. This property is preserved for structural systems with many supports, where only the lower modes of the earthquake, usually the first two POD modes, are responsible for the structural response. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
6.
Izuru Takewaki 《地震工程与结构动力学》2001,30(9):1345-1360
Earthquake ground motions and their effects on structural responses are very uncertain even with the present knowledge. It is therefore desirable to develop a robust structural design method taking into account these uncertainties. Critical excitation approaches are promising and a new random critical excitation method is proposed for MDOF elastic–plastic shear‐building structures on compliant ground. The power (area of power spectral density (PSD) function) and the intensity (magnitude of PSD function) are fixed and the critical excitation is found under these restrictions. In contrast to linear elastic structures, transfer functions and simple expressions for response evaluation cannot be defined in elastic–plastic structures and difficulties arise in describing the peak responses except by laborious elastic–plastic time‐history response analysis. Statistical equivalent linearization is used to estimate the elastic–plastic stochastic peak responses approximately. The critical excitation responses are obtained for several examples and compared with those of the corresponding recorded earthquake ground motion. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
7.
为了在众多参数中挑选其中最有代表性的参数,来解释和反映脉冲型地震动对结构的潜在破坏能力,以338条脉冲型地震动记录作为研究对象,分析地震动参数与中低层结构响应的相关性。选取了14个常用地震动参数,对各地震动参数之间的相关性进行分析,从中选出7个代表性地震动参数;并将脉冲型地震动输入中低层结构模型中计算结构响应,分析代表性地震动参数与结构响应的相关性,与基于非脉冲型地震动的相关性计算结果进行对比。选用了3层和7层2个RC框架结构作为中低层结构代表,其基本周期为0.62s和0.89s。结果表明:对于脉冲型地震动,对于3层结构时与结构响应相关性最好的为EPV,对于7层结构时与结构响应相关性最好的为PGV,因此可以用PGV和EPV作为表征脉冲型地震动对中低层结构潜在破坏能力的参数;而对于非脉冲型地震动,与结构响应相关性最好的参数为PGV,可以用PGV作为表征脉冲型地震动对中低层结构的潜在破坏能力的参数。因此,通过地震动参数来解释和表征脉冲型地震动对结构的破坏能力是可行的。 相似文献
8.
9.
确定地震动输入样本容量是开展结构动力地震反应分析的重要环节,目前国内外关于地震动输入样本容量的讨论往往忽略或尚难以定量考虑结构地震反应估计的可靠度水平。以一实际钢筋混凝土框架结构为例,首先分析在大样本地震动作用下结构非线性地震反应的统计特征,研究估计结构地震反应时取样本最大值和平均值的差异,然后借助于假设检验分析结构地震反应的概率分布模型,给出基于一致可靠度的地震动样本容量确定方法,并对比分析单周期点、多周期点、谱值匹配调整地震动及人工合成地震动对样本容量需求的影响,为保证在小样本地震动输入下结构地震反应估计值满足给定可靠度和容许误差提供分析方法和判断依据。本文方法适应于定量确定不同结构类型和不同地震强度水平下的地震动样本容量需求,对建筑结构抗震性能评估及设计规范研究有一定意义。 相似文献
10.
The rocking response of large flexible structures to earthquakes 总被引：1，自引：0，他引：1
The rocking response of structures subjected to strong ground motions is a problem of ‘several scales’. While small structures are sensitive to acceleration pulses acting successively, large structures are more significantly affected by coherent low frequency components of ground motion. As a result, the rocking response of large structures is more stable and orderly, allowing effective isolation from the ground without imminent danger of overturning. This paper aims to characterize and predict the maximum rocking response of large and flexible structures to earthquakes using an idealized structural model. To achieve this, the maximum rocking demand caused by different earthquake records was evaluated using several ground motion intensity measures. Pulse-type records which typically have high peak ground velocity and lower frequency content caused large rocking amplitudes, whereas non-pulse type records caused random rocking motion confined to small rocking amplitudes. Coherent velocity pulses were therefore identified as the primary cause of significant rocking motion. Using a suite of pulse-type ground motions, it was observed that idealized wavelets fitted to velocity pulses can adequately describe the rocking response of large structures. Further, a parametric analysis demonstrates that pulse shape parameters affect the maximum rocking response significantly. Based on these two findings, a probabilistic analysis method is proposed for estimating the maximum rocking demand to pulse-type earthquakes. The dimensionless demand maps, produced using these methods, have predictive power in the near-field provided that pulse period and amplitude can be estimated a priori. Use of this method within a probabilistic seismic demand analysis framework is briefly discussed. 相似文献
11.
The response and damage assessment of engineering structures under near-field ground motions is currently of great interest. Near-field ground motion with directivity focusing or fling effects produces pulse-like ground motion that has characteristics different from those of ordinary records. This paper develops simple deterministic and probabilistic models for near-field pulse-like ground motions. These models belong to the class of engineering models that aim to replicate some of the gross features observed in near-field records. The ground velocity is expressed as a steady-state function or a stationary random process modulated by an envelope function. Both models account for the non-stationarity and the multiple pulses in the ground velocity. While the deterministic model is similar to some of the models developed earlier, the probabilistic model facilitates handling uncertainties in the ground motion and variability in the structure's properties. For instance, this model combined with structural reliability methods can be used for reliability assessment of structures under near-field random ground motion. The reduction of the structural response by adding supplemental dampers is also investigated. 相似文献
12.
It is commonly understood that earthquake ground excitations at multiple supports of large dimensional structures are not the same. These ground motion spatial variations may significantly influence the structural responses. Similarly, the interaction between the foundation and the surrounding soil during earthquake shaking also affects the dynamic response of the structure. Most previous studies on ground motion spatial variation effects on structural responses neglected soil–structure interaction (SSI) effect. This paper studies the combined effects of ground motion spatial variation, local site amplification and SSI on bridge responses, and estimates the required separation distances that modular expansion joints must provide to avoid seismic pounding. It is an extension of a previous study (Earthquake Engng Struct. Dyn. 2010; 39 (3):303–323), in which combined ground motion spatial variation and local site amplification effects on bridge responses were investigated. The present paper focuses on the simultaneous effect of SSI and ground motion spatial variation on structural responses. The soil surrounding the pile foundation is modelled by frequency‐dependent springs and dashpots in the horizontal and rotational directions. The peak structural responses are estimated by using the standard random vibration method. The minimum total gap between two adjacent bridge decks or between bridge deck and adjacent abutment to prevent seismic pounding is estimated. Numerical results show that SSI significantly affects the structural responses, and cannot be neglected. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
13.
Studies of structural responses and damage to high-frequency blast motion are very limited. Current practice uses some empirical allowable ground vibration limits in assessing structural performance. These empirical limits overlook the physical parameters that govern structural response and damage, such as the ground motion characteristics and inherent structural properties. This paper studies the response of RC frame structures to numerically simulated underground blast-induced ground motions. The structural response and damage characteristics of frame structures to ground motions of different frequencies are investigated first. The effects of blast ground motion spatial variations and soil–structure interaction on structural responses are also studied. A suitable discrete model that gives accurate response prediction is determined. A damage index defined based on the accumulated plastic hinge rotation is used to predict structural damage level. Numerical results indicated that both the low structural vibration modes (global modes) and the first elemental vibration mode (local) might govern the dynamic structural responses depending on the ground motion frequency and structural response parameters under consideration. Both ground motion spatial variations and soil–structure interaction effects are prominent. Neglecting them might yield inaccurate structural response prediction. The overall structural response and damage are highly ground motion frequency dependent. Numerical results of structural damage are also compared with some test results obtained in a previous study and with code specifications. Discussions on the adequacy of the code allowable ground vibration limits on RC frame structures are also made. 相似文献
14.
G. N. Bycroft 《地震工程与结构动力学》1980,8(5):397-404
Differential ground motions due to horizontally propagating surface waves are of importance in determining the stresses and displacements developed in extended structures such as large mat foundations for nuclear power stations, dams, bridges and pipe-lines. A general method is developed for determining the motion of a large rigid mat foundation subjected to travelling surface waves and observations made on the relative displacements of individual foundations and their importance in bridge failure. 相似文献
15.
大跨空间结构由于其体量大且多作为人流密集的公共场所,因而在各种非常规荷载作用下破坏将造成更大的经济损失、人员伤亡和社会影响。系统的从以下3个方面总结了近年来大跨空间结构抗震理论所取得的主要进展:(1)大跨空间结构精细化的抗震性能评估理论,主要包括材料本构模型、地震动多点输入和结构强非线性模拟;(2)大跨空间结构抗震性能提升与修复技术,主要包括结构减震技术和隔震技术的研究与应用;(3)大跨空间结构抗震设计理论与方法,主要包括基于性态的设计方法和功能可恢复性的抗震设计方法。通过以上部分的系统总结和论述,形成大跨空间结构统一的抗震设计指导思想,并对此类结构的抗震研究的发展趋势和方向进行展望,从而为大跨空间结构设计、施工和监测提供借鉴。 相似文献
16.
双向地震动作用的拟等延性系数谱 总被引：1，自引：0，他引：1
首先建立了以强度折减系数表述的恢复力特性满足二维屈服面模型的理想弹塑性单质点系统(它在2个相互垂直的主轴方向上分别具有水平平动自由度)在双向地震动作用下的归一化运动方程。然后引入单向地震动作用下等延性系数的强度折减系数谱,给出了双向地震动作用的拟等延性系数谱(定义为系统分别承受双向和单向地震动作用,在同一主轴方向上的最大位移反应之比)最后通过硬土场地10组双向地震动记录拟等延性系数谱的统计平均结果,分析了结构周期、位移延性系数和阻尼等因素对谱值及结构双向地震反应的影响。结果表明,双向地震动作用与单向地震动作用相比主要增加结构较长周期方向的最大位移反应。若在基于位移的抗震设计中降低结构较短周期方向的设计位移延性系数,可在一定程度上降低双向地震动的不利影响。因定义的谱为比值形式,阻尼对其影响不大。 相似文献
17.
本文在对实际地震加速度记录统计分析的基础上,给出了能够合理描述地震动强度非平稳特性的参数及其取值范围;然后引入实验设计方法,建立了适合于地震动强度非平稳特性参数分析的实验设计算法,用来分析地震动强度非平稳特性参数的变化对结构响应的影响;最后通过与近似技术相结合,建立了地震动强度非平稳特性参数与结构响应之间的近似定量关系模型.结果表明,本文提出的实验设计方法适合于对地震动强度非平稳特性参数进行分析,该方法在有效地减小计算量的同时,获得了结构响应与参数变化之间的对应关系.基于实验设计方法进行的特性参数方差分析结果表明:地震动的稳态持时对结构地震响应的影响比较显著;对于周期较小的结构,特性参数之间的交互作用对结构地震响应的影响显著,但当周期大于1 s时,则不显著.本文建立的近似定量关系模型能够较好地反映不同特性参数、不同周期结构动力响应之间的联系,为工程实践中基于结构特性合理设置地震动特性参数、合成或挑选地震加速度时程提供理论依据. 相似文献
18.
The effect of the vertical component of ground motion on the horizontal response of a sliding system is studied. Soil–foundation interaction is included. The results indicate that the effect of vertical motion is significant in the cascs of harmonically excited foundations. 相似文献
19.
A novel ground motion selection and modifications method to perform response history analysis of structures is presented in this paper. Currently, the accessibility of ground motion information permits the analysis of structures using real ground motion data. Predicting the dynamic behavior of structures is a primary objective; therefore, the selection of a set of ground motions that shows a reduction in the variability of the structural response and accuracy in preserving the median demand is a challenging task. The new selection and scaling procedure emerges from comparing a set of horizontal ground motions at various ranges of frequency. In this study, the conditional mean spectrum and the design response spectrum are used as target spectra, and the records that give an applicable and compelling contribution to the hazard are considered. It is possible to obtain a set of ground motions with similar seismic severity by matching the target spectrum at the period of interest T ref , where the scaled spectrum should have an equivalent Housner intensity in the period range 0.2T ref –2T ref . The horizontal components for every band of frequency is obtained using a specific index that depends on the energy-frequency trend’s shape as well as on its scattering degree around the mean value. This allows obtaining a set of spectrum-compatible records with almost identical severity and low dispersion of the structural response parameters. The methodology has been tested showing a significant effectiveness in terms of low variability of parameters and accuracy in preserving the median demand for a given hazard scenario. 相似文献
20.
The paper examines the effect on the structural response of the inevitable correlation which exists between the six earthquake components acting along a set of structural axes. The rotational components are expressed in terms of the spatial derivatives of the translational components. For the calculation of response, modal analysis is employed so that ground response spectra can also be used as seismic input. A methodology is developed to obtain the maximum mean square response which can occur in a structure, irrespective of its orientation with respect to the impinging seismic waves. The application of this methodology for the calculation of design response is advocated, especially for asymmetric structures. For the assumed model of seismic wave motion, the numerical results show a significant contribution to the response from the rotational components. This contribution is, however, expected to be reduced by structural foundation averaging and interaction effects. Further studies with more complete models of seismic wave motions, and their interaction with structural foundations, are thus warranted for a realistic evaluation and characterization of the rotational inputs for design purposes. 相似文献