共查询到20条相似文献，搜索用时 421 毫秒
1.
A spherical model of the Earth including a heterogeneous upper mantle and excited by the magnetic field of a magnetospheric ring current is constructed. The obtained synthetic data are used for testing a new approach to gradient geomagnetic sounding ensuring the immunity of the sought impedance to distortions caused by lateral heterogeneity of the Earth. It is shown that this approach significantly increases the informativeness of deep electromagnetic sounding. 相似文献
2.
本文采用Novak薄层法推导粘弹性地基的扭转动力阻抗,并将其用于考虑桩土相互作用的单桩扭转动力阻抗,又通过传递矩阵法将此公式推广到求取层状地基单桩扭转动力阻抗。而且本文以工程中常用的端承桩为例,推导了层状地基中端承桩扭转动力阻抗的简化计算公式。根据此公式,分析了频率、上覆软土层厚度、上覆软土层刚度等因素对单桩扭转动力阻抗的影响,分析结果表明,随着振动频率提高,层状地基中端承单桩的扭转动力阻抗的实部有缓慢下降的趋势,而虚部则增大;随着上覆土层厚度的增加,层状地基中端承单桩的扭转动力阻抗的实部和虚部均减小;随着上覆土层刚度的减小,层状地基中端承单桩的扭转动力阻抗的实部减小,虚部在低频段减小,而在较高频率段则增大。 相似文献
3.
Morteza Eskandari-Ghadi Azizollah Ardeshir-Behrestaghi 《Soil Dynamics and Earthquake Engineering》2010
This paper is concerned with the investigation of the vertical vibration of a rigid circular disc buried at an arbitrary depth in a transversely isotropic half space in such a way the axis of material symmetry of the half space is normal to the surface of it and parallel to the vibration direction. By using the Hankel integral transforms, the mixed boundary-value problem is transformed to a pair of integral equations called dual integral equations, which generally can be reduced to a Fredholm integral equation of the second kind. With the aid of complex variable or contour integration, the governing integral equation is numerically solved in the general dynamic case. Two degenerated cases (i) the disc is buried in a transversely isotropic full space, and (ii) rigid circular disc is attached on the surface of the half space are discussed. The reduced static case of the dual integral equations is solved analytically and the vertical displacement, the contact pressure and the static impedance/compliance function are explicitly found. It is shown that the vertical pressure and the compliance function reduced for isotropic half space are identical to the previous solutions reported in the literature. The dynamic contact pressure under the disc and the impedance function are numerically evaluated in general dynamic case and graphically shown that the singularity exists in the contact pressure at the edge of the disc is the same as the static case. In addition, the impedance functions evaluated here for the isotropic domain are collapsed on the solution given by Luco and Mita. To show the effect of different material anisotropy, the numerical evaluations are given for some different transversely isotropic materials and compared. 相似文献
4.
Summary In this work we study the effects on the surface impedance of a one-dimensional structure, caused by a perturbation due to the introduction of a deep perfect reflector.An algorithm for presenting the impedance in a rational polynomial form is outlined and the properties concerning the location of poles and zeros, corresponding to this function, are investigated. It is shown that perturbing the structure by the introduction of a perfect reflector at any finite depth will affect the analytic behaviour of the surface impedance for any frequency range. 相似文献
5.
6.
Mettupalayam V. Sivaselvan Andrei M. Reinhorn Xiaoyun Shao Scot Weinreber 《地震工程与结构动力学》2008,37(15):1785-1800
A new approach to dynamic force control of mechanical systems, applicable in particular to frame structures, over frequency ranges spanning their resonant frequencies is presented. This approach is implemented using added compliance and displacement compensation. Hydraulic actuators are inherently velocity sources, that is, an electrical signal regulates their velocity response. Such systems are therefore by nature high‐impedance (mechanically stiff) systems. In contrast, for force control, a force source is required. Such a system logically would have to be a low‐impedance (mechanically compliant) system. This is achieved by intentionally introducing a flexible mechanism between the actuator and the structure to be excited. In addition, in order to obtain force control over frequencies spanning the structure's resonant frequency, a displacement compensation feedback loop is needed. The actuator itself operates in closed‐loop displacement control. The theoretical motivation, as well as the laboratory implementation of the above approach is discussed along with experimental results. Having achieved a means of dynamic force control, it can be applied to various experimental seismic simulation techniques such as the effective force method and the real‐time dynamic hybrid testing method. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
7.
桩基—非线性框剪结构相互作用体系（上）——群桩阻抗函数的求取 总被引：4，自引：0，他引：4
为研究桩基－非线性框剪结构相互作用体系的地震反应,需要求解群桩基础的动力阻抗函数。本文利用单桩阻抗和群桩动力相互作用因子计算群桩动力阻抗函数,计算并讨论了不同构形群桩阻抗函数在软、中和硬土地基中的变化规律和特点。研究表明：群桩阻抗表现出很强的频率相关性,随土体剪切波速的增大,群桩阻抗有较大幅度的增加,但土体剪切波速的变化对群桩效率（规格化阻抗函数）影响不大。 相似文献
8.
二相介质饱和土中群桩动力阻抗分析 总被引：4，自引：0，他引：4
用流体饱和多孔介质材料描述土体，由饱和土和群桩及承台系统的位移协调条件和力平衡条件建立饱和土和群桩及承台系统动力相互作用的控制方程，分析饱和土中群桩动力阻抗。结果表明：孔隙流体对饱和土中桩基础动力阻抗有一定的影响；在饱和土具有不同的流体渗透系数时，饱和土中群桩动力阻抗也有一定差别。在地基上与基础结构动力相互作用研究中应该考虑地基土中孔隙流体的影响。 相似文献
9.
The problem of the dynamic response of rigid embedded foundations subjected to the action of external forces and seismic excitation is analysed. It is shown that to calculate the response of rigid embedded foundations, or the response of flat rigid foundations subjected to non-vertically incident seismic waves, it is necessary to obtain not only the impedance matrix for the foundation, but also the forces induced by the incident seismic waves. Under these general conditions, rocking and torsional motion of the foundation is generated in addition to translation. The case of a two-dimensional rigid foundation of semi-elliptical cross-section is used as an example to illustrate the effects of the embedment depth and angle of incidence of the seismic waves on the response of the foundation. 相似文献
10.
A. V. Guglielmi 《Izvestiya Physics of the Solid Earth》2009,45(9):740-743
The paper is dedicated to the 70th anniversary of the formulation of the Leontovich impedance boundary condition. This boundary
condition is applied in geophysics for sounding of the lithosphere and diagnostics of the magnetosphere by electromagnetic
waves. The use of the Leontovich condition is shown to open new possibilities for investigating the anharmonicity of MHD oscillations
of the magnetosphere. The differential impedance equation, which is derived with the aid of the Leontovich boundary condition,
can prove useful in the investigation of the electroconductivity of the lithosphere by the method of inductive sounding. It
is shown within the framework of a simple model that the method of the Leontovich parabolic equation makes it possible to
find a correction to the Leontovich boundary condition caused by the fact that, in general, the relation between the horizontal
components of an electromagnetic field is not local. It is shown that the anharmonicity of MHD oscillations of the magnetosphere
coupled with the nonlocality of the boundary condition on the Earth’s surface can lead to an apparent nonlinearity of the
surface impedance calculated in accordance with the classical technique of magnetotelluric sounding. 相似文献
11.
《地震工程与工程振动(英文版)》2015,(3)
A dynamic model test(CL = 4) at different velocities of train,namely different loading frequencies,is carried out to study the dynamic characteristics of a high-speed railway tunnel invert and its foundation soils.Not only are the accelerations,dynamic coefficients,dynamic stresses of the invert and foundation soils emphatically analyzed,their relationship with the velocity of the train are discussed in detail.Through laboratory testing,the attenuation of vibration propagating from up the rails is obtained and the calculation formula of the speed influence coefficient of the tunnel invert is preliminarily established.The depth of the foundation soils influenced by vibration is also determined in this study.It is shown that the responses of the tunnel invert and foundation soils to vibration are slightly increased with the velocity of the train;circumferential stresses in the bottom of the invert are tensile stresses and maximum stresses appear under the foot of the rails;the dynamic soil pressures of the foundation decrease quickly with the distance away from the tunnel invert and an exponential relationship exists between them. 相似文献
12.
THE DISPERSION RELATION, OF EARTH''S ELECTROMAGNETIC RESPONSE FUNCTIONS AND THE JOINT INVERSION OF DATA 
下载免费PDF全文
下载免费PDF全文 On the basis of the dispersion relations of MT field, the necessity and applied prospects of the joint inversions using a pair of MT response functions which are correlative with the dispersion relations, are infered. A filter coefficient algorithm is made, with which the corresponding impedance phase data can be estimated using a set of apparent resistivities. The tests for the observed MT data show that when comparing the impedance phase estimated using the dispersion relation with the ob served phase, it can be checked whether the dispersion relation between observed apparent resistivity and phase data is satisfied or not, and that the use of the phase data corrected using the dispersion relation in the joint inversion is advantageous to obtain more confident results. It is shown that joint inversions are more advantageous than single parameter inversions, and that in the most case the joint inversion using the apparent resistivities of impedance real and imaginary parts is more advantageous than the jointinversion using the normal apparent resistivity and impedance phase. The existence of the dipersion relations between the ratio apparent resistivity and corresponding impedance phase of the orthogonal electric and magnetic field horizontal Components in the frequency EM sounding with horizontal electric dipole(FEMS) are discussed, the better effect of the joint inversion using the pair of EM response functions is obtained. The problems on the one-dimensional joint inversion for the MT and FEMS apparent resistivities, for which the observed frequency bands partly overlape each other, are studied. It is shown that this joint inversion is applicable and effective:the joint inversions of the practical data for two kinds of EM methods at two sites give the results well corresponding to the drilling data. The simulated MT inversions for the data of two kinds of EM methods are made, and more confident results also are obtained. 相似文献
13.
The ultimate goal of reservoir simulation in reservoir surveillance technology is to estimate long-term production forecasting and to plan development and management of petroleum fields. However, maintaining reliable reservoir models which honour available static and dynamic data, involve inherent risks due to the uncertainties in space and time of the distribution of hydrocarbons inside reservoirs. Recent applications have shown that these uncertainties can be reduced by quantitative integration of seismic data into the reservoir modelling workflows to identify which areas and reservoir attributes of the model should be updated. This work aims using seismic data to reduce ambiguity in calibrating reservoir flow simulation model with an uncertain petro-elastic model, proposing a circular workflow of inverted seismic impedance (3D and 4D) and engineering studies, with emphasis on the interface between static and dynamic models. The main contribution is to develop an updating procedure for adjusting reservoir simulation response before using it in the production forecasting and enhance the interpretive capability of reservoir properties. Accordingly, the workflow evaluates consistency of reservoir simulation model and inverted seismic impedance, assisted by production history data, to close the loop between reservoir engineering and seismic domains. The methodology is evaluated in a complex, faulted, sandstone reservoir, the Norne benchmark field, where a significant reservoir behaviour understanding (about the static and dynamic reservoir properties) is obtained towards the quantitative integration of seismic impedance data. This leads to diagnosis of the reservoir flow simulation reliability and generation of an updated simulation model consistent with observed seismic and well production history data, as well as a calibrated petro-elastic model. Furthermore, as Norne Field is a benchmark case, this study can be considered to enrich the discussions over deterministic or probabilistic history matching studies. 相似文献
14.
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
15.
Experimental investigation on the seismic performance of PP-band strengthening stone masonry houses 总被引：1，自引：0，他引：1
Navaratnarajah Sathiparan Kotaro Sakurai Muneyoshi Numada Kimiro Meguro 《Bulletin of Earthquake Engineering》2013,11(6):2177-2196
The collapse of stone masonry is one of the greatest causes of death in major earthquake events around the world. This paper investigates a recently developed retrofitting technology specifically aimed at preventing or prolonging the collapse of stone masonry buildings under strong earthquakes. This technology uses common polypropylene packaging straps to form a mesh, which is then used to prevent or prolong collapse. This paper examines the findings from static and dynamic testing of the proposed retrofit. It is shown that the proposed technique effectively prevents brittle masonry collapse and the loss of debris. 相似文献
16.
在常温、固体围压介质(铅)三轴压缩的条件下,采用磁带记录的快速数据采集系统,对完整的居庸关花岗岩、迁安石英岩和含不同角度锯切面的居庸关花岗岩试件的突发失稳动态过程进行了实验研究。结果表明,当试件沿内部斜面快速错动而突发失稳时,表现为各点应力和位移的振动、衰减,并趋于新的稳定终止态。根据应力和位移的记录,得到了应力-应变(相对位移)动态合成图。以失稳振动的初动半周期为界,可将整个动态过程划分为摩擦错动阶段和自由振动阶段。实验还表明,突发失稳岩石的动态错距等于或近似于终态错距。实测的动态应力降约为终态应力降的1.6倍。 相似文献
17.
Stability of the time‐domain analysis method including a frequency‐dependent soil–foundation system 下载免费PDF全文
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
18.
The analytical solution, for the H-polarization magnetotelluric impedance, of a series of multiple, vertical, conducting slabs (dikes) embedded in a host medium is extended to an infinite array in order to model an anisotropic layer. The solution is used to study the effects of such strongly anisotropic media on the surface impedance. At low frequencies such vertically laminated structures behave as a bulk material. It is shown that the effective bulk parameters are those expected from d.c. theory. However, practical electrode separations may not be long enough or adequately positioned to correctly obtain these bulk parameters from the measured impedance. Thus, such structures can masquerade as quite different one-dimensional structures. A haphazard use of long electrode spacings will not necessarily produce correct results. 相似文献
19.
This paper describes an experimental program to examine the force–displacement behavior of a class of multi‐spherical sliding bearings. The primary goal of the experiments is to test the validity of the theory developed in a companion paper that describes the behavior of these devices. Experimental work consisted of testing the three primary variations of these bearings in several configurations of different friction and displacement capacities. Most tests were carried out at slow speeds; however, some testing was also conducted at high speed (up to approximately 400 mm/s) to examine the behavior under dynamic conditions. The results of experimental testing were generally found to be in very good agreement with the analytical results. It is shown that the forces and displacements at which transitions in stiffness occur are predictable and therefore controllable in design. Furthermore, the underlying principles of operation were confirmed by the fact that starting and stopping of sliding on the different surfaces occurred as expected from theory. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
20.
A variant of the Rosenbrock‐W integration method is proposed for real‐time dynamic substructuring and pseudo‐dynamic testing. In this variant, an approximation of the Jacobian matrix that accounts for the properties of both the physical and numerical substructures is used throughout the analysis process. Only an initial estimate of the stiffness and damping properties of the physical components is required. It is demonstrated that the method is unconditionally stable provided that specific conditions are fulfilled and that the order accuracy can be maintained in the nonlinear regime without involving any matrix inversion while testing. The method also features controllable numerical energy dissipation characteristics and explicit expression of the target displacement and velocity vectors. The stability and accuracy of the proposed integration scheme are examined in the paper. The method has also been verified through hybrid testing performed of SDOF and MDOF structures with linear and highly nonlinear physical substructures. The results are compared with those obtained from the operator splitting method. An approach based on the modal decomposition principle is presented to predict the potential effect of experimental errors on the overall response during testing. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献