共查询到20条相似文献，搜索用时 15 毫秒
1.
Shuenn-Yih Chang 《地震工程与结构动力学》1997,26(9):917-929
There is no second-order accurate, dissipative, explicit method in the currently available step-by-step integration algorithms. Two new families of second-order accurate, dissipative, explicit methods have been successfully developed for the direct integration of equations of motion in structural dynamics. These two families of methods are numerically equivalent and possess the desired numerical dissipation which can be continuously controlled. These two families of algorithms are very useful for pseudodynamic tests since the favourable numerical damping can be used to suppress the spurious growth of high-frequency modes due to the presence of numerical and/or experimental errors in performing a pseudodynamic test. © 1997 by John Wiley & Sons, Ltd. 相似文献
2.
Implementation and application of the unconditionally stable explicit parametrically dissipative KR‐α method for real‐time hybrid simulation 
下载免费PDF全文
下载免费PDF全文 Chinmoy Kolay James M. Ricles Thomas M. Marullo Akbar Mahvashmohammadi Richard Sause 《地震工程与结构动力学》2015,44(5):735-755
In real‐time hybrid simulations (RTHS) that utilize explicit integration algorithms, the inherent damping in the analytical substructure is generally defined using mass and initial stiffness proportional damping. This type of damping model is known to produce inaccurate results when the structure undergoes significant inelastic deformations. To alleviate the problem, a form of a nonproportional damping model often used in numerical simulations involving implicit integration algorithms can be considered. This type of damping model, however, when used with explicit integration algorithms can require a small time step to achieve the desired accuracy in an RTHS involving a structure with a large number of degrees of freedom. Restrictions on the minimum time step exist in an RTHS that are associated with the computational demand. Integrating the equations of motion for an RTHS with too large of a time step can result in spurious high‐frequency oscillations in the member forces for elements of the structural model that undergo inelastic deformations. The problem is circumvented by introducing the parametrically controllable numerical energy dissipation available in the recently developed unconditionally stable explicit KR‐α method. This paper reviews the formulation of the KR‐α method and presents an efficient implementation for RTHS. Using the method, RTHS of a three‐story 0.6‐scale prototype steel building with nonlinear elastomeric dampers are conducted with a ground motion scaled to the design basis and maximum considered earthquake hazard levels. The results show that controllable numerical energy dissipation can significantly eliminate spurious participation of higher modes and produce exceptional RTHS results. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
3.
The novel doubly asymptotic multi-directional transmitting boundary combines the advantages of the doubly asymptotic and multi-directional formulations. It is rigorous for the low-frequency limit (static case) and the high-frequency limit in the wave-propagation direction perpendicular to the artificial boundary and at all the preselected angles corresponding to various apparent velocities. It is implemented straightforwardly in the finite-element method. The doubly asymptotic multi-directional transmitting boundary is temporally local and spatially either global or local depending on the implementation of the static-stiffness matrix. It leads to much higher accuracy than other transmitting boundaries with the same finite-element mesh. 相似文献
4.
The single, long and narrow channel that usually connects choked coastal lagoons to the ocean can serve as a natural hydraulic low-pass filter that reduces or eliminates tidal and subtidal effects inside the lagoon. This study proposes an alternative method of estimating the attenuation of the tidal and subtidal oscillations throughout the Patos Lagoon estuary. The attenuation is estimated for conditions of contrasting river runoff and weather (summer and winter). A high-pass/low-pass filter (fast fourier transformation technique – FFT) is applied to time series of sea-surface elevation (SSE) measured at the mouth of the Patos Lagoon. The resulting high-frequency (tidal) and low-frequency (subtidal) signals are used in independent simulations to force the TELEMAC-2D model. Attenuation of the tidal and subtidal signals throughout the estuary is estimated by applying cross-spectral analysis between the model-generated SSE time series at different locations throughout the estuary and the filtered SSE time series measured at the mouth. Results from the proposed method suggest that: (1) the low-frequency (subtidal) oscillations are less attenuated and propagate further than the high-frequency (tidal) oscillations in the Patos Lagoon estuary; (2) the filtering capability of the Patos Lagoon estuary is expected to follow a seasonal pattern, although further investigations on an interannual time scale are recommended in order to confirm this hypothesis; (3) the influence of the oceanic boundary processes on the SSE dynamics of the lagoon is restricted to the lower estuary. Further inland, the local forcing generated by the wind and freshwater input is likely to be the main forcing effect controlling the dynamics of the system. The proposed method proved to be an efficient and alternative way of estimating the attenuation of energy in the tidal and subtidal bands throughout the access channel of a choked coastal lagoon located in an area of reduced tidal influence.Responsible Editor: Iris Grabemann 相似文献
5.
S. M. Molodensky 《Izvestiya Physics of the Solid Earth》2008,44(7):519-526
Asymptotic analysis of low-frequency oscillations of a rotating liquid bounded by a solid surface is performed under the condition
that the oscillation frequency is much smaller than the angular rate of rotation. Simple analytical relations describing comprehensively
asymptotic modes of these oscillations are obtained. 相似文献
6.
A new energy density calculation method for reservoir delineation using seismic low-frequency signal
Xin Luo Xuehua Chen Yingkai Qi Jidong Yang Jie Zhang Wei Jiang 《Geophysical Prospecting》2020,68(8):2518-2535
In comparison to high-frequency signals, low-frequency seismic signals suffer less from scattering and intrinsic attenuation during wave propagation, penetrate deeper strata and thus can provide more energy information related to the hydrocarbon reservoirs. Based on the asymptotic representation for the frequency-dependent reflections in the fluid-saturated pore-elastic media, we first derive a novel equation of the reservoir energy density and present an efficient workflow to calculate the reservoir energy density using low-frequency seismic data. Then, within a low-frequency range (from 1 to 30 Hz), we construct an objective function to determine the optimal frequency, using the energy densities calculated from the post-stack seismic traces close to the wells. Next, we can calculate the reservoir energy density using the instantaneous spectra of optimal frequency at the low-frequency end of the seismic spectrum. Tests on examples for synthetic and field data demonstrate that the proposed reservoir energy density can produce high-quality images for the fluid-saturated reservoirs, and it produces less background artefacts caused by elastic layers. This method provides a new way to detect the location of hydrocarbon reservoirs and characterize their spatial distribution. 相似文献
7.
The mathematical methods of direct spectral analysis were employed for the database that was drawn from the monitoring of well # 30 during 2004 in order to obtain the amplitude-frequency function of steam-water mixture pressure in the Verkhne-Mutnovskii hydrothermal system (the depth at which pressure was measured was 950 m, the time interval between measurements was 2 min, resulting in a total of about 250000 determinations). We identified large-scale and small-scale types of pressure variability. The large-scale variability reflects the low-frequency component of the variation and is seen as macro-fluctuations involving considerable (as large as 2 bars), sudden or gradual pressure changes. The small-scale variability consists of both irregular and regular oscillations. Medium-frequency and high-frequency components can be identified in the latter variability. The medium-frequency component consists of gradual fluctuations with periods of about 20 min (a frequency of 0.00083 Hz), with the maximum pressure changes between measurements being 0.7 bars. The high-frequency component consists of sudden pressure changes (drops, rises, or spikes), as well as of fluctuations with periods below 5 min. 相似文献
8.
叠前地震资料中,高频分量和低频分量随传播距离的衰减特性不同.本文给出了一种在小波域定性估计叠前地震资料衰减参数的方法.该方法利用连续小波变换提取共反射点道集的高、低频分量,以低频分量和高频分量之差定性反映地震波的衰减.通过累加不同偏移距的衰减,提高了估计的稳定性;采用幅度归一化方法,降低了信号幅值对衰减参数估计的影响.将本文提出方法与常用的基于叠后地震资料衰减估计方法用于某油田的地震资料处理,结果表明,本文方法得到的衰减估计结果能够更好地反映油气的空间展布. 相似文献
9.
The inconsistency of records of local earthquakes and synthetic seismograms due to noise contamination of the data and/or to improper Green function because of an inexact structural model often results in high frequency oscillations of the source time function, which prolongs it spuriously. A priori limit on the roughness of the source time function turned out to reduce the spurious oscillations but it keeps its spurious extension unchanged. Thus, it may yield a severe distortion of the seismic moment. However, it reduces the spurious volumetric component of the mechanism resulting from improper modelling of the structure and, thus, may help decide whether the retrieved volumetric component is real or false. The demand for the smoothness is incorporated as a penalty function in the minimization of the least square residuals, which allows us to decide about the degree of the smoothness. The minimization is performed with a simple genetic algorithm, which offers the advantage of a detailed exploration of the model space reducing the danger of being trapped in local minima. 相似文献
10.
Introduction There are various factors affecting the propagation of earthquake waves. Usually these fac- tors include the earthquake source, the path and the site effects. Simulations of the earthquake wave propagation and the strong ground motion are an adequate way to exhibit these factors (Virieux, 1986; Levander, 1988; Frankel and Vidale, 1992; Frankel, 1993; Graves, 1993, 1996a; Olsen et al, 1995; Pitarka et al, 1996; Pitarka, 1999). The most popular numerical method in use is the gri… 相似文献
11.
An innovative method of analysis was developed to simulate the non-linear seismic finite-amplitude liquid sloshing in two-dimensional containers. In view of the irregular and time-varying liquid surface, the method employed a curvilinear mesh system to transform the non-linear sloshing problem from the physical domain with an irregular free-surface boundary into a computational domain in which rectangular grids can be analysed by the finite difference method. Non-linearities associated with both the unknown location of the free surface and the high-order differential terms were considered. The Crank–Nicolson time marching scheme was employed and the resulting finite difference algorithm is unconditionally stable and very lightly damped with respect to the temporal co-ordinate. In order to minimize numerical instability caused by the computational dispersion in spatially discretized surface wave, a second-order dissipation term was added to the system to filter out the spurious high-frequency waves. Sloshing effects and structural response were measured in terms of sloshing amplitude, base shear and overturning moment generated by the hydrodynamic pressure of the liquid exerted on the container walls. Simulation results of liquid sloshing induced by earthquake and harmonic base excitations were compared with those of the linear wave theory and the limitations of the latter in assessing the response of seismically excited liquids were addressed. 相似文献
12.
13.
《Advances in water resources》2005,28(2):117-133
Difficulty in solving the transient advection–diffusion equation (ADE) stems from the relationship between the advection derivatives and the time derivative. For a solution method to be viable, it must account for this relationship by being accurate in both space and time. This research presents a unique method for solving the time-dependent ADE that does not discretize the derivative terms but rather solves the equation analytically in the space–time domain. The method is computationally efficient and numerically accurate and addresses the common limitations of numerical dispersion and spurious oscillations that can be prevalent in other solution methods. The method is based on the improved finite analytic (IFA) solution method [Lowry TS, Li S-G. A characteristic based finite analytic method for solving the two-dimensional steady-state advection–diffusion equation. Water Resour Res 38 (7), 10.1029/2001WR000518] in space coupled with a Laplace transformation in time. In this way, the method has no Courant condition and maintains accuracy in space and time, performing well even at high Peclet numbers. The method is compared to a hybrid method of characteristics, a random walk particle tracking method, and an Eulerian–Lagrangian Localized Adjoint Method using various degrees of flow-field heterogeneity across multiple Peclet numbers. Results show the IFALT method to be computationally more efficient while producing similar or better accuracy than the other methods. 相似文献
14.
近断层地震动的向前方向性效应和永久地面位移效应导致其速度时程表现为长周期、大峰值的速度脉冲,其位移时程表现为阶跃型脉冲. 针对这些特点,同时考虑向前方向性效应和永久地面位移效应,提出了一种简单的、连续函数形式表达的等效速度脉冲模型. 在该模型中,包含描述速度脉冲周期、峰值和形状的5个待定参数,方便了实际脉冲型地震记录的拟合及模拟. 等效速度脉冲模型只包含单一的频率成分,不能反映脉冲型地震记录的高频成分. 根据对11次地震28条地震记录的分析, 速度脉冲的频率一般小于1Hz. 因此, 在模拟脉冲型地震记录的方法中,分别模拟低频脉冲成分和高频成分,并将两者叠加生成近断层脉冲型地震动的模拟时程. 相似文献
15.
Sébastien Blaise Benjamin de Brye Anouk de Brauwere Eric Deleersnijder Eric J. M. Delhez Richard Comblen 《Ocean Dynamics》2010,60(3):535-554
At high Peclet number, the residence time exhibits a boundary layer adjacent to incoming open boundaries. In a Eulerian model,
not resolving this boundary layer can generate spurious oscillations that can propagate into the area of interest. However,
resolving this boundary layer would require an unacceptably high spatial resolution. Therefore, alternative methods are needed
in which no grid refinement is required to capture the key aspects of the physics of the residence time boundary layer. An
extended finite element method representation and a boundary layer parameterisation are presented and tested herein. It is
also explained how to preserve local consistency in reversed time simulations so as to avoid the generation of spurious residence
time extrema. Finally, the boundary layer parameterisation is applied to the computation of the residence time in the Scheldt
Estuary (Belgium/The Netherlands). This timescale is simulated by means of a depth-integrated, finite element, unstructured
mesh model, with a high space–time resolution. It is seen that the residence time temporal variations are mainly affected
by the semi-diurnal tides. However, the spring–neap variability also impacts the residence time, particularly in the sandbank
and shallow areas. Seasonal variability is also observed, which is induced by the fluctuations over the year of the upstream
flows. In general, the residence time is an increasing function of the distance to the mouth of the estuary. However, smaller-scale
fluctuations are also present: they are caused by local bathymetric features and their impact on the hydrodynamics. 相似文献
16.
Simulation method of near-fault pulse-type ground motion 总被引：1，自引：0，他引：1
Introduction With the development of the economy of China, it is possible to build large-span bridges, pipelines, dams and other lifeline structures in the seismically active regions or through the active faults. In addition, some isolated and energy diss… 相似文献
17.
A. W. Hurst 《Bulletin of Volcanology》1998,60(1):1-9
Virtually all the seismicity within Ruapehu Volcano recorded during a 2-month deployment in early 1994, with 14 broadband
seismographs around the Tongariro National Park volcanoes in the North Island of New Zealand, was associated with the active
vent and occurred within approximately 1 km of Ruapehu Crater Lake. High-frequency volcano-tectonic earthquakes and low-frequency
events (similar to bursts of 2 Hz volcanic tremor) were both found to have sources in this region. The high-frequency events,
which often consisted of a smaller precursor event followed approximately 2 s later by the main event, had sharp onsets and
were locatable using standard techniques. The depth of these events ranged from the surface down to approximately 1500 m below
Crater Lake. The low-frequency events did not have sharp onsets and were located by phase-correlation methods. Nearly all
occurred under a small region on the east side of Crater Lake, at depths from 200 to 1000 m below the surface. This low-frequency
earthquake source region, in which no high-frequency events occurred, may be the steam zone within the actual vent of Ruapehu
Volcano.
Received: 30 June 1996 / Accepted: 16 February 1998 相似文献
18.
采用短时单频脉冲震源的浅地层剖面,记录的波形数据空间假频较严重。因其信号具有频率高、频带窄的特征,通常利用Hiibert变换提取瞬时振幅属性（信号包络）供解释使用。但瞬时振幅均为正值,在进行构造解释时不方便使用。本文提出在对浅层剖面资料提取瞬时振幅的基础上,计算瞬时振幅的微分并配合滤波的方法,实现高频窄带浅地层剖面资料的一种频移处理。该方法把高频窄带的多周期信号变为低频带宽的单周期信号,有效扩展了倍频程并消除假频。应用在南海浅地层剖面资料处理中,资料处理后更利于构造解释。 相似文献
19.
The application of Maslov asymptotic theory in a general 3-D mixed subspace of 6-D complex phase space is proposed to obtain the integral superpositions of Gaussian packets and beams. The ray method and the superposition of plane waves (Maslov method of Chapman and Drumond [7]) are special limiting cases of the above mentioned approach. The same high-frequency asymptotic expansion formulae for seismic body waves were derived previously in [8] using the Gaussian beam method. 相似文献