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1.
Introduction Estimation of an attenuation relationship for strong ground motion parameters has been an interesting research subject in the field of engineering seismology and has played a very important role in seismic safety evaluation, seismic zoning, seismic hazard evaluation of major constructions, etc. At present, the generally used parameters include peak acceleration, peak velocity and elastic response spectrum. Such parameters mentioned above are essentially independent of the duration… 相似文献
2.
This paper deals with the estimation of peak inelastic displacements of SDOF systems, representative of typical steel structures, under constant relative strength scenarios. Mean inelastic deformation demands on bilinear systems (simulating moment resisting frames) are considered as the basis for comparative purposes. Additional SDOF models representing partially‐restrained and concentrically‐braced (CB) frames are introduced and employed to assess the influence of different force‐displacement relationships on peak inelastic displacement ratios. The studies presented in this paper illustrate that the ratio between the overall yield strength and the strength during pinching intervals is the main factor governing the inelastic deformations of partially‐restrained models and leading to significant differences when compared with predictions based on bilinear structures, especially in the short‐period range. It is also shown that the response of CB systems can differ significantly from other pinching models when subjected to low or moderate levels of seismic demand, highlighting the necessity of employing dedicated models for studying the response of CB structures. Particular attention is also given to the influence of a number of scalar parameters that characterise the frequency content of the ground motion on the estimated peak displacement ratios. The relative merits of using the average spectral period Taver, mean period Tm, predominant period Tg, characteristic period Tc and smoothed spectral predominant period To of the earthquake ground motion, are assessed. This paper demonstrates that the predominant period, defined as the period at which the input energy is maximum throughout the period range, is the most suitable frequency content scalar parameter for reducing the variability in displacement estimations. Finally, noniterative equivalent linearisation expressions based on the secant period and equivalent damping ratios are presented and verified for the prediction of peak deformation demands in steel structures. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
3.
利用266条强震记录,在研究绝对输入能量谱和相对输入能量谱衰减规律的基础上,对由衰减关系所确立的两种输入能量谱进行对比分析,讨论了延性系数对这两种输入能量谱的影响. 研究发现,在弹性情况下,两种输入能量谱在周期0.5~1.0 s范围内相差不大; 在非弹性情况下 两种输入能量谱在周期0.5 s处相差不大. 周期较小时,绝对输入能量谱要大于相对输入能量谱;周期较大时,绝对输入能量谱小于相对输入能量谱. 延性系数对这两种输入能量谱影响均比较大, 对绝对输入能量谱而言,周期小于0.3 s时,随着延性系数的增大, 能量谱升高;周期大于0.3 s时,随着延性系数的增大能量谱降低. 不同延性系数的绝对输入能量谱在分界点0.3 s左右相等. 相对输入能量谱受延性系数影响与绝对输入能量谱相似, 但分界点在0.5 s左右. 与绝对输入能量谱相比, 相对输入能量谱在短周期段受延性系数的影响较大, 特别是当场地较软时更为明显. 相似文献
4.
Quantification of ground-motion parameters and response spectra in the near-fault region 总被引：2，自引：1，他引：1
R. Rupakhety S. U. Sigurdsson A. S. Papageorgiou R. Sigbj?rnsson 《Bulletin of Earthquake Engineering》2011,9(4):893-930
This study focuses on the characteristics of near-fault ground motions in the forward-direction and structural response associated
with them. These ground motions are narrow-banded in nature and are characterized by a predominant period at which structures
excited by them are severely affected. In this work, predominant period is defined as the undamped natural period of a single-degree-of-freedom
(SDOF) oscillator at which its 5% damped linear elastic pseudo-spectral velocity (PSV) contains a clear and dominant peak. It is found that a linear relationship exists between predominant period and seismic
moment. An empirical equation describing this relationship is presented by using a large set of accelerograms. Attenuation
equations are developed to estimate peak ground velocity (PGV) as a function of earthquake magnitude and source-to-site distance. In addition, a predictive equation for spectral shapes
of PSV (i.e., PSV normalized by PGV) is presented as a continuous function of the undamped natural period of SDOF oscillators. The model is independent of PGV, and can be used in conjunction with any available PGV attenuation relation applicable to near-fault ground motion exhibiting forward-directivity effects. Furthermore, viscous
damping of the SDOF is included in the model as a continuous parameter, eliminating the use of so-called damping correction
factors. Finally, simple equations relating force reduction factors and displacement ductility of elasto-plastic SDOF systems
are presented. 相似文献
5.
Jun Iyama 《地震工程与结构动力学》2005,34(15):1799-1815
The response of an elasto‐plastic single degree of freedom (SDOF) system to ground motion is estimated based on wavelet coefficients calculated by discrete wavelet transform. Wavelet coefficients represent both the time and frequency characteristics of input ground motion, and thus can be considered to be directly related to the dynamic response of a non‐linear system. This relationship between the energy input into an elastic SDOF system and wavelet coefficients is derived based on the assumption that wavelets deliver energy to the structure instantaneously and the quantity of energy is constant regardless of yielding. These assumptions are shown to be valid when the natural period of the system is in the predominant period range of the wavelet, the most common scenario for real structures, through dynamic response analysis of a single wavelet. The wavelet‐based estimation of elastic and plastic energy transferred by earthquake ground motion is thus shown to be in good agreement with the dynamic response analysis when the natural period is in the predominant range of the input. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
6.
The seismic response of single‐degree‐of‐freedom (SDOF) systems incorporating flag‐shaped hysteretic structural behaviour, with self‐centring capability, is investigated numerically. For a SDOF system with a given initial period and strength level, the flag‐shaped hysteretic behaviour is fully defined by a post‐yielding stiffness parameter and an energy‐dissipation parameter. A comprehensive parametric study was conducted to determine the influence of these parameters on SDOF structural response, in terms of displacement ductility, absolute acceleration and absorbed energy. This parametric study was conducted using an ensemble of 20 historical earthquake records corresponding to ordinary ground motions having a probability of exceedence of 10% in 50 years, in California. The responses of the flag‐shaped hysteretic SDOF systems are compared against the responses of similar bilinear elasto‐plastic hysteretic SDOF systems. In this study the elasto‐plastic hysteretic SDOF systems are assigned parameters representative of steel moment resisting frames (MRFs) with post‐Northridge welded beam‐to‐column connections. In turn, the flag‐shaped hysteretic SDOF systems are representative of steel MRFs with newly proposed post‐tensioned energy‐dissipating connections. Building structures with initial periods ranging from 0.1 to 2.0s and having various strength levels are considered. It is shown that a flag‐shaped hysteretic SDOF system of equal or lesser strength can always be found to match or better the response of an elasto‐plastic hysteretic SDOF system in terms of displacement ductility and without incurring any residual drift from the seismic event. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
7.
本文对具有旗帜型滞回模型的单自由度自复位体系提出了设计能量谱的构造方法,包括设计输入能量谱和设计滞回耗能比谱。首先按中国规范场地类别选取360条实际强震记录进行时程分析,对影响单自由度自复位体系输入能量谱和滞回耗能比谱的参数,包括地震波类型、滞回模型、阻尼比、延性系数等进行研究。在此基础上分别建议了设计输入能量谱和设计滞回耗能比谱及其曲线参数的确定方法,并与实际强震记录计算结果进行比较。结果表明结构滞回模型对能量谱影响明显;阻尼比和延性系数对输入能量谱的影响在整个周期范围内有显著差异,但均有明显的削峰作用。建议的两种设计能量谱综合考虑了结构参数、地震波参数和中国场地类别的影响,可以较好的拟合实际情况,并对弹塑性单自由度自复位体系在地震作用下的耗能需求做出较准确的估计。 相似文献
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The sensitivity of seismic energy dissipation to ground motion and system characteristics is assessed. It is found that peak ground acceleration, peak ground velocity to acceleration (V/A), dominant period of ground excitation and effective response duration are closely correlated with the energy dissipated by a SDOF system. Ductility ratio and damping ratio have no significant influence on the energy dissipation. An energy dissipation index is proposed for measuring the damage potential of earthquake ground motion records which includes the effects of basic excitation and response characteristics contributing to the seismic energy dissipation. The proposed index is compared with several intensity measures for the set of 94 ground motion records considered in the study. 相似文献
10.
In this paper, we present a post-processing technique and an a posteriori error estimate for the Newmark method in structural dynamic analysis. By post-processing the Newmark solutions, we derive a simple formulation for linearly varied third-order derivatives. By comparing the Newmark solutions with the exact solutions expanded in the Taylor series, we achieve the local post-processed solutions which are of fifth-order accuracy for displacements and fourth-order accuracy for velocities in one step. Based on the post-processing technique, a posteriori local error estimates for displacements, velocities and, thus, also the total energy norm error estimate are obtained. If the Newmark solutions are corrected at each step, the post-processed solutions are of third-order accuracy in the global sense, i.e. one-order improvement for the original Newmark solutions is achieved. We also discuss a method for estimating the global time integration error. We find that, when the total energy norm is used, the sum of the local error estimates will give a reasonable estimate for the global error. We present numerical studies on a SDOF and a 2-DOF example in order to demonstrate the performance of the proposed technique. 相似文献
11.
In order to investigate the response of structures to near‐fault seismic excitations, the ground motion input should be properly characterized and parameterized in terms of simple, yet accurate and reliable, mathematical models whose input parameters have a clear physical interpretation and scale, to the extent possible, with earthquake magnitude. Such a mathematical model for the representation of the coherent (long‐period) ground motion components has been proposed by the authors in a previous study and is being exploited in this article for the investigation of the elastic and inelastic response of the single‐degree‐of‐freedom (SDOF) system to near‐fault seismic excitations. A parametric analysis of the dynamic response of the SDOF system as a function of the input parameters of the mathematical model is performed to gain insight regarding the near‐fault ground motion characteristics that significantly affect the elastic and inelastic structural performance. A parameter of the mathematical representation of near‐fault motions, referred to as ‘pulse duration’ (TP), emerges as a key parameter of the problem under investigation. Specifically, TP is employed to normalize the elastic and inelastic response spectra of actual near‐fault strong ground motion records. Such normalization makes feasible the specification of design spectra and reduction factors appropriate for near‐fault ground motions. The ‘pulse duration’ (TP) is related to an important parameter of the rupture process referred to as ‘rise time’ (τ) which is controlled by the dimension of the sub‐events that compose the mainshock. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
12.
The effects of soil–structure interaction (SSI) while designing the liquid column damper (LCD) for seismic vibration control of structures have been presented in this study. The formulation for the input–output relation of a flexible‐base structure with attached LCD has been presented. The superstructure has been modelled by a single‐degree‐of‐freedom (SDOF) system. The non‐linearity in the orifice damping of the LCD has been replaced by equivalent linear viscous damping by using equivalent linearization technique. The force–deformation relationships and damping characteristics of the foundation have been described by complex valued impedance functions. Through a numerical stochastic study in the frequency domain, the various aspects of SSI on the functioning of the LCD have been illustrated. A simpler approach for studying the LCD performance considering SSI, using an equivalent SDOF model for the soil–structure system available in literature by Wolf (Dynamic Soil–Structure Interaction. International Series in Civil Engineering and Engineering Mechanics. Prentice‐Hall: Englewood Cliffs, NJ, 1985) has also been presented. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
13.
The stationary response of base-isolated buildings subjected to earthquake excitation is studied. The frequency content of earthquake input is described by the Clough-Penzien spectral model. The response parameters of interest are (1) the root-mean-square (RMS) displacement σx of the basement relative to the foundation (i.e. shear deformation of the isolation system) and (2) the ratio (σa/σa0) of the RMS value of the absolute acceleration at the roof of the isolated structure over the corresponding value when the isolation system is locked. The variation of these response parameters with the effective frequency f0 of the base-isolated structure is investigated. As input, earthquakes with moment magnitudes M = 7-3 and M = 6-0 are considered. The acceleration spectra corresponding to these two earthquake sizes have pronouncedly different frequency content over the frequency range 0–1-1–0 Hz which is of primary importance for base-isolated structures. An important conclusion that comes from these analyses is that confidence in the effectiveness of a base-isolated system should be based primarily on its capacity to absorb/dissipate energy and less on its influence in shifting the fundamental period of the structure out of the range of dominant earthquake energy. 相似文献
14.
This paper presents a single-degree-of-freedom (SDOF) constitutive model for assessing the performance of freestanding block contents of buildings. The model incorporates a bespoke damper to account for energy dissipation associated with rocking. It is advantageous in its direct correlation, via energy conservation, to the restitution coefficient for impact during rocking. A comparative study with the existing SDOF rocking models shows that the proposed model significantly improves the accuracy of free-rocking simulations, in which inherent damping predominantly affects response. It provides a promising and efficient tool for computationally intensive performance evaluation of nonstructural components.
相似文献15.
The main purpose of this paper is to study the collapse capacity of single degree of freedom(SDOF) systems and to produce fragility curves as well as collapse capacity spectra while considering a broad range of structural parameters, including system degradation, the P-Δ effect, ductility capacity and the post-capping stiffness ratio. The modified IbarraKrawinkler deterioration model was used to consider hysteretic behavior. A comprehensive study was conducted to extract the collapse capacity spectrum of SDOF systems with a wide range of periods, varying from 0.05 to 4 s, to cover short, intermediate and long periods. Incremental dynamic analysis(IDA) was performed for SDOF systems to identify the condition in which the collapse capacity of the system is determined. The IDAs were performed using different sets of seismic ground motions. The ground motion records were categorized into different sets based on three spectral shape parameters, including the epsilon, Sa Ratio and N_p. The collapse fragility curves of SDOF systems with different periods were extracted to illustrate the collapse capacity at different probability levels. The results show that structural degradation and ductility as well as the spectral shape parameters significantly affect the collapse capacity of SDOF systems. On the other hand, the post-capping stiffness ratio and small levels of the P-Δ effect do not remarkably change collapse capacity. Also, the collapse capacity of SDOF systems is more sensitive to the records categorized based on Sa Ratio and N_p than those classified based on epsilon. 相似文献
16.
Based on the results of an extensive parametric study of elastic and inelastic response of SDOF systems, in which the most important structural parameters were varied and ground motions of very different characteristics were taken into account, simple formulae for determining the seismic demand in SDOF systems with natural periods in the medium- and long-period range are proposed. Seismic demand is expressed in terms of the mean values of maximum relative displacements and maximum input energy. These results can be used to provide rough estimates of structural behaviour when different damage models are applied. As well as this, the proposed formulae can be used to construct design spectra of the Newmark-Hall type. 相似文献
17.
Changhai Zhai Duofa Ji Weiping Wen Cuihua Li Weidong Lei Lili Xie 《地震工程与工程振动(英文版)》2018,17(2):277-291
Structures located in seismically active regions may be subjected to mainshock-aftershock (MSAS) sequences. Strong aftershocks significantly affect the hysteretic energy demand of structures. The hysteretic energy, EH,seq, is normalized by mass m and expressed in terms of the equivalent velocity, VD,seq, to quantitatively investigate aftershock effects on the hysteretic energy of structures. The equivalent velocity, VD,seq, is computed by analyzing the response time-history of an inelastic single-degree-of-freedom (SDOF) system with a varying vibration period subjected to 309 MSAS sequences. The present study selected two kinds of MSAS sequences, with one aftershock and two aftershocks, respectively. The aftershocks are scaled to maintain different relative intensities. The variation of the equivalent velocity, VD,seq, is studied for consideration of the ductility values, site conditions, relative intensities, number of aftershocks, hysteretic models, and damping ratios. The MSAS sequence with one aftershock exhibited a 10% to 30% hysteretic energy increase, whereas the MSAS sequence with two aftershocks presented a 20% to 40% hysteretic energy increase. Finally, a hysteretic energy prediction equation is proposed as a function of the vibration period, ductility value, and damping ratio to estimate hysteretic energy for mainshock-aftershock sequences. 相似文献
18.
Application of support vector machine and relevance vector machine to determine evaporative losses in reservoirs 总被引：1，自引：0，他引：1
This article employs Support Vector Machine (SVM) and Relevance Vector Machine (RVM) for prediction of Evaporation Losses (E) in reservoirs. SVM that is firmly based on the theory of statistical learning theory, uses regression technique by introducing ε‐insensitive loss function has been adopted. RVM is based on a Bayesian formulation of a linear model with an appropriate prior that results in a sparse representation. The input of SVM and RVM models are mean air temperature (T) ( °C), average wind speed (WS) (m/sec), sunshine hours (SH)(hrs/day), and mean relative humidity (RH) (%). Equations have been also developed for prediction of E. The developed RVM model gives variance of the predicted E. A comparative study has also been presented between SVM, RVM and ANN models. The results indicate that the developed SVM and RVM can be used as a practical tool for prediction of E. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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Under the assumption that hydrograph generation was affected by n linear reservoirs with the same value of storage coefficient k, Nash proposed the formulation of the Instantaneous Unit Hydrograph (IUH), which has been widely used in rainfall–runoff simulation and flood forecasting. However, the assumption of the parameter k having the same value in all reservoirs is obviously unphysical as it results in the estimated value of n not being integral. In this study, for parameter n integral, the different k value for each reservoir was derived using the Laplace transform and developing a general rule for the equation of the IUH of any order. The relationship between parameter k and the slope of the river channel estimated using digital elevation model (DEM) data is established, the parameter estimation procedures are given. As in most unit hydrograph studies, only isolated storm events are considered here. Seventeen flood events in three catchments were selected for the case studies. Application results show that the proposed method is slightly better than Nash's IUH with higher model efficiency and smaller absolute relative errors. This work provides a new methodology for the formulation of the IUH. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献