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impedance-functions
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Passively realisable impedance functions by using two fractional elements and some resistors
, Article IET Circuits, Devices and Systems ; Volume 12, Issue 3 , 2018 , Pages 280-285 ; 1751858X (ISSN) ; Sharif University of Technology
Institution of Engineering and Technology
2018
Abstract
Here, the necessary and sufficient conditions for realisability of a general class of impedance functions by passive electrical networks composed of two fractional element (fractional capacitor or fractional inductor) and some resistors are found. Also, a systematic procedure is proposed to obtain such passive electrical networks in the realisable cases. Moreover, by establishing a connection with the previously reported researches on the subject of inerter-based passive mechanical control, further results on the maximum number of the resistors required for passive realisation are obtained. Furthermore, a numerical example is presented to show the usefulness of the paper achievements in...
An inextensible membrane at the interface of a transversely isotropic bi-material full-space
, Article International Journal of Engineering Science ; Volume 91 , June , 2015 , Pages 34-48 ; 00207225 (ISSN) ; Khojasteh, A ; Mohammadnezhad, H ; Rahimian, M ; Pak, R. Y. S ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
A theoretical formulation is presented for the determination of the dynamic interaction of a horizontally loaded inextensible circular membrane embedded at the interface of a transversely isotropic bi-material full-space, using cylindrical co-ordinate system and applying Hankel integral transforms in the radial direction and Fourier series, the problem will be changed to a system of four separate integral equations, which, in turn, are reduced to a pair of Fredholm equations of the second kind that are amenable to numerical treatments. The impedance functions have been evaluated in dynamic case, which can be directly used in soil-structure-interaction and engineering problems. It is shown...
Investigation of Dynamic Response of Shallow Foundations on Sandy Soil to Horizontal Harmonic Loading by Physical Model Tests
, M.Sc. Thesis Sharif University of Technology ; Jafarzadeh, Fardin (Supervisor)
Abstract
The most important step in current dynamic analysis of machine foundations is determining dynamic impedance functions. Impedance functions are defined as ratios of applied force or moment to induced displacement or rotation angle of foundation. In this research, horizontal dynamic response of foundation on homogeneous halfspace was investigated using physical modeling. Soil medium was built in a 1mx1mx0.8m steel box whose interior walls were covered by 0.1m of sawdust (a material with high damping). In order to prevent possible reflection of waves, this cover was extended to the box bottom with 0.2 m thickness. Sand raining method was used to build soil medium. In this method, with...
Numerical Study of Dynamic Response of Shallow Foundations to Vertical Loads Induced by Machines
, M.Sc. Thesis Sharif University of Technology ; Ahmadi, Mohammad Mehdi (Supervisor)
Abstract
The main purpose of designing machine foundation is to limit its motion to such an amount that not to prevent the perfect workability of machine, not to let the foundation strains exceed the elastic limit and also not to disturb the persons working around the machine. The key note in successfull design of machine foundation, is to precisely analyse the response of foundation to dynamic loads induced by machine operations.The numerical study of shallow foundations response to vertical harmonic loads induced by machinaries have been discussed in this investigation.To aim this purpose, FLACD3D has been utilized in order to 3 dimensionally analyse a continuum medium comprising soil-foundation or...
Investigation of Dynamic Response of Shallow Foundations on Layered Soil Medium by Physical Modeling
, M.Sc. Thesis Sharif University of Technology ; Jafarzadeh, Fardin (Supervisor)
Abstract
Dynamic impedance functions method is most recent approach in the analysis of soil-foundation dynamic interaction, and presented for massless rigid foundations. Impedance functions are frequency dependent functions, and used to obtain dynamic response of foundation with arbitrary mass subjected to dynamic loading of any frequency and magnitude. The important assumptions for appropriate useof mentioned method are rigidity of foundation and visco-elastic behavior of the soil beneath the foundation. In this study, experimental vertical impedance functions of square and circular foundations have been investigated,using physical modeling tests. A granular soil layer with finite thickness...
Study of the Dynamic Response of Foundation Resting on Sandy soil by Means of Physical Modeling
, M.Sc. Thesis Sharif University of Technology ; Jafarzadeh, Fardin (Supervisor)
Abstract
Experimental investigations in the subject of dynamic response of machine foundations for verification of many theoretical studies are scant. The effects of several factors, namely, shape and weight of foundation, frequency of vibration, depth of embedment, dynamic load levels and type of loading (harmonic and impact) on dynamic response of foundation were studied experimentally.Also, the current methods of machine foundation analysis mostly are based on the concept of the dynamic impedance function. Therefore, using these tests results, impedance functions for the model are calculated and presented. The physical model tests were carried out in a steel container with dimension of 1×1×0.9 m....
Probabilistic Output-Only Identification of Soil-Structure Systems Using Shear Beam Model
, M.Sc. Thesis Sharif University of Technology ; Mahsuli, Mojtaba (Supervisor) ; Ghahari, Farid (Co-Supervisor)
Abstract
This paper proposes a novel probabilistic framework for output-only identification of a soil-structure system. The system is modeled by a vertical shear beam resting on the soil representative springs. The proposed framework estimates the unknown parameters of the system and the foundation input motion time history simultaneously, using sparsely measured responses of the structure. The unknown parameters of the system include stiffness of the sway and rocking springs, shear modulus of the beam, and the modal damping ratios of the system. These parameters are modeled as random variables whose joint probability distribution is updated in a Bayesian scheme using the observations of structural...
Passively realizable approximations of non-realizable fractional order impedance functions
, Article Journal of the Franklin Institute ; Volume 357, Issue 11 , 2020 , Pages 7037-7053 ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Approximating the fractional order differentiation and integration operators is a common approach in implementation of fractional order dynamics. This paper aims to investigate how the procedure of approximating the fractional order operators influences on the realizability of a fractional order impedance function by passive networks. To this aim, conditions for the possibility of passive realization of the approximations of the fractional order impedance functions by using RLC components are obtained. More precisely, considering two general forms for the filters approximating the fractional order operators, the open mapping theorem in complex analysis is applied to obtain the realizability...
Dynamic impedance functions of machine foundations on sandy soils by physical model tests
, Article Proceedings of the 17th International Conference on Soil Mechanics and Geotechnical Engineering: The Academia and Practice of Geotechnical Engineering, 5 October 2009 through 9 October 2009, Alexandria ; Volume 1 , 2009 , Pages 478-481 ; 9781607500315 (ISBN) ; Mashhadi, H. G ; Sharif University of Technology
Abstract
In order to improve new methods of design of machine foundations by means of impedance function, implementation of experimental investigations to calibrate these methods is vital. The physical model tests were carried out in a steel container with dimension of 1×1×0.9 m. The Babolsar sand was employed in the model. To eliminate reflection of elastic waves, a sawdust layer was used in the lateral walls and bottom of the container. Also, in order to have homogeneous medium with unified density, air pluviation of sand method was employed. Response of the models to harmonic excitations was measured using various instruments deployed around the foundation. Results of the tests are shown in the...
Investigation of Dynamic Response of Foundations on Sandy Soils to Two-Way Horizontal Harmonic Loading by Physical Model Tests
, M.Sc. Thesis Sharif University of Technology ; Jafarzadeh, Fardin (Supervisor)
Abstract
Increasing requirements of industries and research institutes to analytical results of interaction soil-foundation related systems, reveals the importance of the dynamic impedance functions than ever before. The dynamic impedance function relations are presented for massless rigid foundations which is possible to obtain dynamic response of foundations for different frequencies and masses accordingly. In this study, the dynamic impedance functions were investigated using physical modeling tests on sandy soil with finite thickness soil stratum over bedrock. The tests were carried out inside a steel container of dimensions 1*1*0.8m in length, width and height respectively which was filled into...
Investigation of Dynamic Response of Shallow Foundations on Layered Soils to Horizontal Harmonic Loading by Physical Model Tests
, M.Sc. Thesis Sharif University of Technology ; Jafarzadeh, Fardin (Supervisor)
Abstract
Increasing requirements of industries and research institutes to analytical results of interaction soil-foundation related systems, reveals the importance of the dynamic impedance functions than ever before. The dynamic impedance function relations are presented for massless rigid foundations which is possible to obtain dynamic response of foundations for different frequencies and masses accordingly. In this study, the dynamic impedance functions were investigated using physical modeling tests on sandy soil with finite thickness soil stratum over bedrock. The tests were carried out inside a steel container of dimensions 110.8m in length, width and height respectively which was filled into...
Probabilistic Identification of Soil-foundation Impedance Function Using Kalman Filter
,
M.Sc. Thesis
Sharif University of Technology
;
Mahsouli, Mojtaba
(Supervisor)
;
Ghahari, Farid
(Co-Supervisor)
Abstract
This paper puts forward a probabilistic approach for simultaneous identification of the dynamic stiffnesses of the soil-foundation and the foundation input motion of soil-structure systems from sparsely-measured structural responses. The soil-structure system in this approach is represented by a shear building resting on sway- and rocking-representative springs and dashpots. The proposed approach employs unknown-input extended Kalman filtering in time domain. This method is built upon Bayesian updating and accounts for two major sources of uncertainty in the problem: the process noise that account for the modeling errors and the measurement noise. In the proposed method, the state vector of...
Realizability of fractional-order impedances by passive electrical networks composed of a fractional capacitor and RLC components
, Article IEEE Transactions on Circuits and Systems I: Regular Papers ; Volume 62, Issue 12 , 2015 , Pages 2829-2835 ; 15498328 (ISSN) ; Tavazoei, M. S ; Sharif University of Technology
Abstract
This paper deals with realization of fractional-order impedance functions by passive electrical networks composed of a fractional capacitor and some RLC components. The necessary and sufficient conditions for the existence of such a realization are found in a general case. Also for impedance functions described by a class of fractional-order transfer functions, the realizability conditions are stated as some algebraic conditions on the parameters of the transfer function. Moreover, a procedure is proposed for implementation of such impedance functions by passive electrical networks composed of a fractional capacitor and some RLC components. Numerical examples are presented to show the...
Passive realization of fractional-order impedances by a fractional element and rlc components: conditions and procedure
, Article IEEE Transactions on Circuits and Systems I: Regular Papers ; Volume 64, Issue 3 , 2017 , Pages 585-595 ; 15498328 (ISSN) ; Tavazoei, M. S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2017
Abstract
In this paper, conditions for checking the realizability of fractional-order impedance functions by passive networks composed of a fractional element (either a fractional capacitor or a fractional inductor) and some RLC components are derived. To this end, at first the newly obtained conditions for realizability of fractional-order impedance functions by a passive network composed of a fractional capacitor and some RLC components are extended to include the case that the polynomials involving in the impedance function can have roots on the imaginary axis. Then, the necessary and sufficient conditions are found on a fractional-order impedance function to be realized by a passive network...
Blind identification of soil-structure systems
, Article Soil Dynamics and Earthquake Engineering ; Volume 45 , February , 2013 , Pages 56-69 ; 02677261 (ISSN) ; Ghannad, M. A ; Taciroglu, E ; Sharif University of Technology
2013
Abstract
Surrounding soil can drastically influence the dynamic response of buildings during strong ground shaking. Soil's flexibility decreases the natural frequencies of the system; and in most cases, soil provides additional damping due to material hysteresis and radiation. The additional damping forces, which are in non-classical form, render the mode shapes of the soil-structure system complex-valued. The response of a soil-foundation system can be compactly represented through impedance functions that have real and imaginary parts representing the stiffness and damping of the system, respectively. These impedance functions are frequency-dependent, and their determination for different...
A discrete model for response estimation of soil-structure systems with embedded foundations
, Article Earthquake Engineering and Engineering Vibration ; Volume 10, Issue 2 , June , 2011 , Pages 263-276 ; 16713664 (ISSN) ; Jahankhah, H ; Ghannad, M. A ; Sharif University of Technology
2011
Abstract
The need for simplified physical models representing frequency dependent soil impedances has been the motivation behind many researches throughout history. Generally, such models are generated to capture impedance functions in a wide range of excitation frequencies, which leads to relatively complex models. That is while there is just a limited range of frequencies that really influence the response of the structure. Here, a new methodology based on the response-matching concept is proposed, which can lead to the development of simpler discrete models. The idea is then used to upgrade an existing simple model of surface foundations to the case of embedded foundations. The applicability of...