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1.
The energy transmitting boundary used in programs such as FLUSH and ALUSH is a very accurate and useful technique for the earthquake response analysis of soil–structure interaction systems. However, it is applicable only to linear analyses or equivalent linear analyses, because it can be calculated only in the frequency domain. The author has proposed methods for transforming frequency-dependent impedance into the time domain. In this paper, an earthquake response analysis method for a soil–structure interaction system, using the energy transmitting boundary in the time domain, is proposed. First, the transform of the transmitting boundary matrices to the time domain using the methods proposed by the author is studied. Then, linear and nonlinear time history earthquake response analyses using the boundary are performed. Through these studies, the validity and efficiency of the proposed methods are confirmed. 相似文献
2.
Naohiro Nakamura 《地震工程与结构动力学》2005,34(11):1391-1406
It is important to estimate the influence of layered soil in soil–structure interaction analyses. Although a great number of investigations have been carried out on this subject, there are very few practical methods that do not require complex calculations. In this paper, a simple and practical method for estimating the horizontal dynamic stiffness of a rigid foundation on the surface of multi‐layered soil is proposed. In this method, waves propagating in the soil are traced using the conception of the cone model, and the impulse response function can be calculated directly and easily in the time domain with a good degree of accuracy. The characteristics of the impedance, that is the transformed value to the frequency domain of the obtained impulse response, are studied using two‐ to four‐layered soil models. The cause of the fluctuation of impedance is expressed clearly from its relation to reflected waves from the lower layer boundary in the model. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
3.
Naohiro Nakamura 《地震工程与结构动力学》2006,35(8):1037-1050
A method to transform the frequency‐dependent complex stiffness to the impulse response in the time domain was proposed in the previous paper. However, there is a problem in that the accuracy and the convergence of the transformed impulse response are not good in some cases. Moreover, the hysteretic damping was not considered in the previous study although it is essential for practical purposes. In this paper, transform method improvements are proposed. First, the accuracy and the convergence are improved by taking the concept of virtual mass into account. Then, a more improved method for transforming the complex stiffness with large hysteretic damping to the time domain is proposed using the least square method. It is well known that the rigorous transform of the hysteretic damping is impossible because it is non‐causal. So this method is thought to be an approximate causalization process. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
4.
Stability of the time‐domain analysis method including a frequency‐dependent soil–foundation system 
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下载免费PDF全文 A number of methods have been proposed that utilize the time‐domain transformations of frequency‐dependent dynamic impedance functions to perform a time‐history analysis. Though these methods have been available in literature for a number of years, the methods exhibit stability issues depending on how the model parameters are calibrated. In this study, a novel method is proposed with which the stability of a numerical integration scheme combined with time‐domain representation of a frequency‐dependent dynamic impedance function can be evaluated. The method is verified with three independent recursive parameter models. The proposed method is expected to be a useful tool in evaluating the potential stability issue of a time‐domain analysis before running a full‐fledged nonlinear time‐domain analysis of a soil–structure system in which the dynamic impedance of a soil–foundation system is represented with a recursive parameter model. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
5.
《地震工程与结构动力学》2018,47(6):1478-1495
In soil‐structure interaction modeling of systems subjected to earthquake motions, it is classically assumed that the incoming wave field, produced by an earthquake, is unidimensional and vertically propagating. This work explores the validity of this assumption by performing earthquake soil‐structure interaction modeling, including explicit modeling of sources, seismic wave propagation, site, and structure. The domain reduction method is used to couple seismic (near‐field) simulations with local soil‐structure interaction response. The response of a generic nuclear power plant model computed using full earthquake soil‐structure interaction simulations is compared with the current state‐of‐the‐art method of deconvolving in depth the (simulated) free‐field motions, recorded at the site of interest, and assuming that the earthquake wave field is spatially unidimensional. Results show that the 1‐D wave‐field assumption does not hold in general. It is shown that the way in which full 3‐D analysis results differ from those which assume a 1‐D wave field is dependent on fault‐to‐site geometry and motion frequency content. It is argued that this is especially important for certain classes of soil‐structure systems of which nuclear power plants subjected to near‐field earthquakes are an example. 相似文献
6.
Der-Wen Chang J. M. Roesset Chan-Hua Wen 《Soil Dynamics and Earthquake Engineering》2000,19(8):157-558
This paper introduces the mathematics and procedures used in developing a time-dependent damping model for integration analyses of structural response. To establish the time-dependent viscous damping model, frequency-dependent damping ratios of the structure under a series of steady-state unit impulses corresponding to actual loads are first calculated. For simplicity, the ratios can be incorporated with the static stiffness of the structure to model approximately the impulse induced damping spectrum. According to the nature of the problem, these ratios can be calculated from the theoretical impedance functions and experimental observations. With the computed damping spectrum, the damping coefficient in the time domain can be obtained with the Fourier transform technique. Adopting the impulse–response method, the damping can be modeled rationally through integration with changing loads. Numerical examples are presented to show the feasibility of this model while the transform criterion is satisfied. 相似文献
7.
Vertical earthquake response of megawatt‐sized wind turbine with soil‐structure interaction effects 下载免费PDF全文
下载免费PDF全文 The dynamic response of a wind turbine on monopile is studied under horizontal and vertical earthquake excitations. The analyses are carried out using the finite element program SAP2000. The finite element model of the structure is verified against the results of shake table tests, and the earthquake response of the soil model is verified against analytical solutions of the steady‐state response of homogeneous strata. The focus of the analyses in this paper is the vertical earthquake response of wind turbines including the soil‐structure interaction effects. The analyses are carried out for both a non‐homogeneous stratum and a deep soil using the three‐step method. In addition, a procedure is implemented which allows one to perform coupled soil‐structure interaction analyses by properly tuning the damping in the tower structure. The analyses show amplification of the ground surface acceleration to the top of the tower by a factor of two. These accelerations are capable of causing damage in the turbine and the tower structure, or malfunctioning of the turbine after the earthquake; therefore, vertical earthquake excitation is considered a potential critical loading in design of wind turbines even in low‐to‐moderate seismic areas. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
8.
We propose an effective and reliable time-domain substructure technique which takes soil-structure interaction effects into account and uses the flexibility coefficients of unbounded soil obtained in the frequency domain. Compared with previous methods, the frequency points to calculate flexibility coefficients, and computational loads in the calculation of time-domain interaction forces, are reduced. In the formulation, we have assumed the flexibility coefficient to be a periodic function, obtained within the bandlimited frequency range, which also includes the predominant frequencies of the structure and incident wave. Then we simulate the periodic flexibility coefficients using discrete impulse responses in the time-domain analyses. However, the real and imaginary parts of the bandlimited flexibility coefficients do not form a Hilbert transform pair; the discrete impulse responses should be modified to be causal for the time-domain analyses. We present various discrete impulse responses which have been obtained from only the real part, only the imaginary part and from both the real and imaginary parts of the frequency-domain flexibility coefficients by FFT with causality conditions. Through a numerical example the relationship between the modified discrete impulse responses and the validity of the time-domain substructure method is presented. 相似文献
9.
10.
A method, based on the Hilbert–Huang spectral analysis, has been proposed by the authors to identify linear structures in which normal modes exist (i.e., real eigenvalues and eigenvectors). Frequently, all the eigenvalues and eigenvectors of linear structures are complex. In this paper, the method is extended further to identify general linear structures with complex modes using the free vibration response data polluted by noise. Measured response signals are first decomposed into modal responses using the method of Empirical Mode Decomposition with intermittency criteria. Each modal response contains the contribution of a complex conjugate pair of modes with a unique frequency and a damping ratio. Then, each modal response is decomposed in the frequency–time domain to yield instantaneous phase angle and amplitude using the Hilbert transform. Based on a single measurement of the impulse response time history at one appropriate location, the complex eigenvalues of the linear structure can be identified using a simple analysis procedure. When the response time histories are measured at all locations, the proposed methodology is capable of identifying the complex mode shapes as well as the mass, damping and stiffness matrices of the structure. The effectiveness and accuracy of the method presented are illustrated through numerical simulations. It is demonstrated that dynamic characteristics of linear structures with complex modes can be identified effectively using the proposed method. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
11.
A procedure for three-dimensional (3-D) coupling of finite elements (FEs), boundary elements (BEs) and infinite boundary elements (IBEs) is presented for the numerical modelling of seismic interaction between arch dams and rock canyons. First, a system of coupling 3-D boundary and infinite boundary elements is developed for simulation of infinite and irregular canyons and for determination, in the frequency domain, of impedance functions on the dam-canyon interface. Secondly, the impedance functions for all degrees-of-freedom are transformed approximately into frequency independent discrete parameters by a curve fitting technique. Finally, these discrete parameters are combined with the dam structure which is discretized by finite elements, thus allowing the response of the arch dam-canyon system to be evaluated. The proposed procedure is efficient because it permits the seismic analysis of arch dam-canyon interaction by the substructure technique in the time domain. To demonstrate both the validity and efficiency of the present procedure, the response of an arch dam-canyon system is obtained under unit impulse acting on the dam-canyon interface as the free field input. Very good agreement is noted when comparing the frequency response determined from the time domain with that from the frequency domain under harmonic excitation applied on the interface of the dam-canyon. 相似文献
12.
Naohiro Nakamura 《地震工程与结构动力学》2008,37(4):495-515
The author has studied the transform method of complex stiffness, which is strongly dependent on frequency, to the time domain. In this paper, new transform methods that use only the real part or the imaginary part data are proposed. By applying them to example problems, it is confirmed that the accuracy of the proposed methods is almost high in both causal and noncausal cases. These methods can also be thought as a standby for the Hilbert transform, because the undefined part is easily calculated by the recovering complex function from the obtained impulse response. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
13.
Masoud Moghaddasi Misko Cubrinovski J. Geoff Chase Stefano Pampanin Athol Carr 《地震工程与结构动力学》2011,40(2):135-154
Complex seismic behaviour of soil–foundation–structure (SFS) systems together with uncertainties in system parameters and variability in earthquake ground motions result in a significant debate over the effects of soil–foundation–structure interaction (SFSI) on structural response. The aim of this study is to evaluate the influence of foundation flexibility on the structural seismic response by considering the variability in the system and uncertainties in the ground motion characteristics through comprehensive numerical simulations. An established rheological soil‐shallow foundation–structure model with equivalent linear soil behaviour and nonlinear behaviour of the superstructure has been used. A large number of models incorporating wide range of soil, foundation and structural parameters were generated using a robust Monte‐Carlo simulation. In total, 4.08 million time‐history analyses were performed over the adopted models using an ensemble of 40 earthquake ground motions as seismic input. The results of the analyses are used to rigorously quantify the effects of foundation flexibility on the structural distortion and total displacement of the superstructure through comparisons between the responses of SFS models and corresponding fixed‐base (FB) models. The effects of predominant period of the FB system, linear vs nonlinear modelling of the superstructure, type of nonlinear model used and key system parameters are quantified in terms of different probability levels for SFSI effects to cause an increase in the structural response and the level of amplification of the response in such cases. The results clearly illustrate the risk of underestimating the structural response associated with simplified approaches in which SFSI and nonlinear effects are ignored. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
14.
A three-dimensional backfill–structure–soil/foundation interaction phenomenon is simulated using the finite element method in order to analyze the dynamic behavior of cantilever retaining wall subjected to different ground motions. Effects of both earthquake frequency content and soil–structure interaction are evaluated by using five different seismic motions and six different soil types. The study mainly consists of three parts. In the first part, following a brief review of the problem, the finite element model with viscous boundary is proposed under fixed-base condition. In the second part, analytical formulations are presented by using modal analysis technique to provide the finite element model verification, and reasonable agreement is found between numerical and analytical results. Finally, the method is extended to further investigate parametrically the effects of not only earthquake frequency content but also soil/foundation interaction, and nonlinear time history analyzes are carried out. By means of changing the soil properties, some comparisons are made on lateral displacements and stress responses under different ground motions. It is concluded that the dynamic response of the cantilever wall is highly sensitive to frequency characteristics of the earthquake record and soil–structure interaction. 相似文献
15.
利用小波多分辨率分析将地震动加速度分解为多频段小波分量,并运用复模态方法推导其计算层间隔震体系在地震作用下的动力响应公式,讨论各频段地震信号及结构响应的能量分配。同时利用小波时频工具分析地震动能量在时频域内的分布对层间隔震结构响应的影响,进而为考察地震动非平稳性对层间隔震结构非线性分析的影响提供方法。利用小波分析的以上优势,对一典型层间隔震结构分别进行弹性和弹塑性分析,结果表明弹性体系在地震作用下的响应可由该地震波各小波分量的响应叠加而得,地震动能量在时间上的集中会对层间隔震结构响应产生不利影响。 相似文献
16.
Site effects characterize the filtering mechanisms within the soil sedimentary layers overlying bedrock. In regions of high seismicity such as California where strong motion records are relatively abundant, site coefficients can be developed by regression of recorded ground shaking parameters. In regions of low‐to‐moderate seismicity or of high seismicity but with a paucity of recorded strong motion data, such empirical models cannot be obtained in the same way. This study describes the theoretical development of a simple, rational manual procedure to calculate site coefficients, based on a single period approximation (SPA), and to construct displacement response spectra (RSD) for soil sites. The proposed simplified model, which takes into account the non‐linear behaviour of soil that is dependent on the level of shaking, impedance contrast at the soil–bedrock interface and the plasticity of soil material, has been verified by comparison with results obtained from non‐linear shear wave analyses and data recorded during the 1994 Northridge earthquake. The proposed model is believed to be a convenient tool for calculating non‐linear site responses and constructing site‐specific response spectra, which has the potential of being incorporated into code provisions. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
17.
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
18.
The response of buried pipelines to random excitation by earthquake forces is obtained using a lumped mass model. The earthquake is considered as a stationary random process characterized by a power spectral density function (PSDF). The cross spectral density function between two random inputs along the length of the pipe is defined with the help of the local earthquake PSDF which is the same for all points, and a frequency dependent exponentially decaying (with distance) function. Soil resistance to dynamic excitation along the pipelength is obtained in an approximate manner with the help of frequency independent impedance functions derived from half-space analysis and Mindlin's static stresses within the soil due to point loads. The proposed method has the advantage that it can take into consideration the cross terms in soil stiffness and damping matrices and can consider any boundary condition that needs to be satisfied at the ends of the pipe. A parametric study is also made to show the influence of cross terms in the soil stiffness and damping matrices on the response of the pipe. 相似文献
19.
Charles Menun 《地震工程与结构动力学》2004,33(9):981-998
A previously developed response‐spectrum‐based procedure for computing the envelope that bounds the time‐varying realizations of Mohr's circle at any prescribed location within a two‐dimensional structure is extended for use with three‐dimensional structures subjected to as many as three translational components of ground acceleration. The proposed envelope, which is completely defined by quantities that are routinely used and calculated in conventional response spectrum analyses, is developed for the general case in which the principal directions of the earthquake, along which the ground accelerations are uncorrelated, are unknown. The accuracy of the proposed envelope is evaluated by comparing it to the results of an ensemble of time‐history analyses performed on a concrete arch dam using simulated accelerograms. It is found that the proposed envelope has a level of accuracy that is suitable for structural design and analysis. The largest observed difference between the simulated and predicted mean envelopes is less than 5%. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
20.
The simultaneous effects of soil–structure interaction, foundation uplift and inelastic behavior of the superstructure on total displacement response of soil–structure systems are investigated. The superstructure is modeled as an equivalent single‐degree‐of‐freedom system with bilinear behavior mounted on a rigid foundation resting on distributed tensionless Winkler springs and dampers. It is well known that the behavior of soil–structure systems can be well described using a limited number of nondimensional parameters. Here, by introducing two new parameters, the concept is extended to inelastic soil–structure systems in which the foundation is allowed to uplift. An extensive parametric study is conducted for a wide range of the key parameters through nonlinear time history analyses. It is shown that while uplifting soil–structure systems experience excessive displacements, in comparison with systems that are not allowed to uplift, ductility demand in the superstructure generally decreases owing to foundation uplift. A new inelastic displacement ratio (IDR) is proposed in conjunction with a nonlinear static analysis of uplifting soil–structure systems. Simplified expressions are also provided to estimate the proposed IDR. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献