Journal articles on the topic 'Dynamic Stiffness Method (DSM)'
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1
Banerjee, J. R. "Review of the dynamic stiffness method for free-vibration analysis of beams." Transportation Safety and Environment 1, no. 2 (November 1, 2019): 106–16. http://dx.doi.org/10.1093/tse/tdz005.
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Abstract The application of the dynamic stiffness method (DSM) for free-vibration analysis of beams is surveyed in this paper. The historical development of the DSM, which has taken place in several stages, is discussed in detail with reference to the free-vibration problems of beams. In particular, the suitability of the DSM in solving the free-vibration problems of beams through the application of the well-known Wittrick–Williams algorithm as a solution technique is highlighted. The literature concerning homogeneous isotropic metallic beams, for which the DSM is well established, is reviewed first, after which, with the rapid and ongoing emergence of advanced composite materials, the development of the DSM in solving the free-vibration problems of anisotropic beams is discussed. The free-vibration analysis of functionally graded beams using the DSM is also highlighted. The survey covers the DSM application for free-vibration analysis of a wide range of beams, including sandwich beams, rotating beams, twisted beams, moving beams and bending-torsion coupled beams, amongst others. Some aspects of the contributions made by the author and his research team are also highlighted. Finally, the future potential of the DSM in solving complex engineering problems is projected.
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Liu, Xiang, Chen Xie, and Han-cheng Dan. "Exact Free Vibration Analysis for Plate Built-Up Structures under Comprehensive Combinations of Boundary Conditions." Shock and Vibration 2020 (March 20, 2020): 1–21. http://dx.doi.org/10.1155/2020/5305692.
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In this research, an exact dynamic stiffness model for spatial plate built-up structures under comprehensive combinations of different boundary conditions is newly proposed. Dynamic stiffness formulations for plate elements with 16 different types of supported opposite edges and arbitrarily supported boundary conditions along other edges are developed, which makes the dynamic stiffness method (DSM) more applicable to engineering problems compared to existing works. The Wittrick–Williams algorithm of the DSM is applied with the explicit expressions of the J0 count for plate elements under all above support conditions. In return, there is no need to refine the element in the DSM, and thus, it becomes immensely efficient. Moreover, the present theory is applied for exact free vibration analysis within the whole frequency range of three built-up structures which are commonly encountered in engineering. The results show that the DSM gives exact results with as much as 100-fold computational efficiency advantage over the commercial finite element method. Besides, benchmark results are also provided.
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Wu, Wenwei, Xuewen Yin, Hui Li, and Kuikui Zhong. "Power flow analysis of built-up plate structures using the dynamic stiffness method." Journal of Vibration and Control 24, no. 13 (February 27, 2017): 2815–31. http://dx.doi.org/10.1177/1077546317695132.
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The dynamic stiffness method (DSM) in our recent paper, which can consider both in-plane and out-of-plane vibrations simultaneously, is formulated to investigate the power flow characteristics of built-up plate structures. Prior to power flow analysis, comprehensive validation works on our DSM are performed so as to better exhibit its numerical capabilities. Power input and power transmission within a two-plate structure are then analyzed by following the context of in-plane and out-of-plane vibrations. In addition, three vibration transmission paths within a multiple plate structure are characterized in terms of power flow densities, which can provide better physical insights in vibration transmission within complex plate structures. Compared to power flow analysis based on the well-known reception/mobility method, our approach is strongly recommended for the dynamics of built-up structures since it can assemble the overall stiffness matrix in a straightforward manner like that in the conventional finite element technique.
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Wu, Nan, Yuzhen Zhao, Qing Guo, and Yongshou Liu. "The effect of two-parameter of Pasternak foundations on the dynamics and stability of multi-span pipe conveying fluids." Advances in Mechanical Engineering 12, no. 11 (November 2020): 168781402097453. http://dx.doi.org/10.1177/1687814020974530.
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In this paper, the dynamics and stability of multi-span pipe conveying fluid embedded in Pasternak foundation is studied. Based on Euler-Bernoulli beam theory, the dynamics of multi-span pipe conveying fluid embedded in two parameters Pasternak foundation is analyzed. The dynamic stiffness method (DSM) is used to solve the control equation. A seven span pipe is calculated. The affection of two parameters of Pasternak foundation is mainly studied. Along with increasing the elastic stiffness K and shear stiffness G, the frequency is also increasing.
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Zhu, Zhihui, Lei Zhang, Wei Gong, Lidong Wang, Yu Bai, and Issam E. Harik. "An efficient hybrid method for dynamic interaction of train–track–bridge coupled system." Canadian Journal of Civil Engineering 47, no. 9 (September 2020): 1084–93. http://dx.doi.org/10.1139/cjce-2019-0020.
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An efficient hybrid method (HM) is proposed by combining the direct stiffness method (DSM) and the mode superposition method (MSM) for analyzing the train–track–bridge coupled system (TTBS). The train and the track are modeled by applying the multi-body dynamics and the DSM, respectively. The bridge is modeled by applying the MSM that is efficient in capturing the dynamic behavior with a small number of modes. The train–track subsystem and the bridge subsystem are coupled by the interaction forces between them. The computational efficiency is significantly improved because of the considerably reduced number of equations of motion of the TTBS. Numerical simulations of a train traversing an arch railway bridge are performed and the results are compared with the field test data and the data from other methods, demonstrating the efficiency and accuracy of the proposed method.
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Chen, Xudong, and Kangsheng Ye. "Comparison Study on the Exact Dynamic Stiffness Method for Free Vibration of Thin and Moderately Thick Circular Cylindrical Shells." Shock and Vibration 2016 (2016): 1–14. http://dx.doi.org/10.1155/2016/9748135.
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Comparison study on free vibration of circular cylindrical shells between thin and moderately thick shell theories when using the exact dynamic stiffness method (DSM) formulation is presented. Firstly, both the thin and moderately thick dynamic stiffness formulations are examined. Based on the strain and kinetic energy, the vibration governing equations are expressed in the Hamilton form for both thin and moderately thick circular cylindrical shells. The dynamic stiffness is assembled in a similar way as that in classic skeletal theory. With the employment of the Wittrick-Williams algorithm, natural frequencies of circular cylindrical shells can be obtained. A FORTRAN code is written and used to compute the modal characteristics. Numerical examples are presented, verifying the proposed computational framework. Since the DSM is an exact approach, the advantages of high accuracy, no-missing frequencies, and good adaptability to various geometries and boundary conditions are demonstrated. Comprehensive parametric studies on the thickness to radius ratio (h/r) and the length to radius ratio (L/r) are performed. Applicable ranges of h/r are found for both thin and moderately thick DSM formulations, and influences of L/r on frequencies are also investigated. The following conclusions are reached: frequencies of moderately thick shells can be considered as alternatives to those of thin shells with high accuracy where h/r is small and L/r is large, without any observation of shear locking.
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Obalareddy, Bharath, Prabhakar Sathujoda, and Roberto Citarella. "Dynamic Stiffness Matrix Approach to Free Vibration Analysis of Functionally Graded Rotor Bearing System Subjected to Thermal Gradients." Materials 15, no. 4 (February 18, 2022): 1540. http://dx.doi.org/10.3390/ma15041540.
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The dynamic stiffness matrix (DSM) method, an analytical method that provides exact solutions, has been used for the first time for the free vibration analysis of a functionally graded (FG) rotor bearing system subjected to temperature gradients and to investigate its application to FG rotors. The material gradation occurs based on the power law between the inner metal core and the outer ceramic rich layer of the FG rotor. The temperature gradation follows the Fourier law of heat conduction which leads to non-linear temperature distribution (NLTD) in the radial direction of the FG rotor. The development of the DSM formulations for Timoshenko FG rotor elements using the governing equations derived from translational and rotational equilibrium conditions is the novelty of the present work. The DSM of the FG rotor elements, rigid disk and linear isotropic bearings are assembled to obtain the global dynamic stiffness matrix of the FG rotor bearing system. The natural whirl frequencies are computed from the global DSM using the Wittrick–William algorithm as a root searching technique. The natural and whirl frequencies are validated with the results available in the literature and the exactness of the DSM method has been exemplified.
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Gaber, Omar, and Seyed M. Hashemi. "Vibration Modeling of Machine Tool Spindles: A Calibrated Dynamic Stiffness Matrix Method." Advanced Materials Research 651 (January 2013): 710–16. http://dx.doi.org/10.4028/www.scientific.net/amr.651.710.
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The effects of spindles vibrational behavior on the stability lobes and the Chatter behavior of machine tools have been established. The service life has been observed to reducethe system natural frequencies. An analytical model of a multi-segment spinning spindle, based on the Dynamic Stiffness Matrix (DSM) formulation, exact within the limits of the Euler-Bernoulli beam bending theory, is developed. The system exhibits coupled Bending-Bending (B-B) vibration and its natural frequencies are found to decrease with increasing spinning speed. The bearings were included in the model usingboth rigid, simply supported, frictionless pins and flexible linear spring elements. The linear spring element stiffness is then calibrated so that the fundamental frequency of the system matches the nominal value.
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Wu, Duan Miao, Guo Jin Chen, and Shao Hui Su. "Research on Large Bulk Carrier Hull Production Design Process Planning Based on Dynamic Stiffness Matrix Method." Applied Mechanics and Materials 333-335 (July 2013): 2270–77. http://dx.doi.org/10.4028/www.scientific.net/amm.333-335.2270.
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According to the shortcomings such as long cycle, large consumption in view of the traditional method of shipbuilding, introduce the method named collaborative design, build hull production design process model. First, decompose hull production design process, then introduce the method of DSM-matrix to describe hull production design task, build the hull production design process model, then based on the model, develop collaborative design system. And use the system to make the hull production design process more reasonable. At last successfully apply them to the collaborative design system. The results suggest that the hull production design method based on DSM-matrix can effectively shorten the manufacturing cycle and save material.
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Erdelyi, Nicholas H., and Seyed M. Hashemi. "A Dynamic Stiffness Element for Free Vibration Analysis of Delaminated Layered Beams." Modelling and Simulation in Engineering 2012 (2012): 1–8. http://dx.doi.org/10.1155/2012/492415.
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A dynamic stiffness element for flexural vibration analysis of delaminated multilayer beams is developed and subsequently used to investigate the natural frequencies and modes of two-layer beam configurations. Using the Euler-Bernoulli bending beam theory, the governing differential equations are exploited and representative, frequency-dependent, field variables are chosen based on the closed form solution to these equations. The boundary conditions are then imposed to formulate the dynamic stiffness matrix (DSM), which relates harmonically varying loads to harmonically varying displacements at the beam ends. The bending vibration of an illustrative example problem, characterized by delamination zone of variable length, is investigated. Two computer codes, based on the conventional Finite Element Method (FEM) and the analytical solutions reported in the literature, are also developed and used for comparison. The intact and defective beam natural frequencies and modes obtained from the proposed DSM method are presented along with the FEM and analytical results and those available in the literature.
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Wei, Zitian, Hui Li, Xuewen Yin, and WenWei Wu. "Vibration Transmission from a Machine with Three Degree of Freedoms to Beam Structures by Dynamic Stiffness Method." Shock and Vibration 2022 (May 16, 2022): 1–18. http://dx.doi.org/10.1155/2022/1956518.
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The dynamic stiffness method (DSM) is proposed for vibration transmission from a machine with three degree of freedoms (DOFs) to its supporting beam structures. The machine is idealized as a rigid mass with three major degrees of freedom, namely, heave, roll, and pitch. It implies that the moments of inertia and torques due to unbalanced parts can be taken into consideration. The three types of vibration within beam structures, i.e., bending, longitudinal, and torsional motions, are formulated in terms of dynamic stiffness matrices. The finite element techniques can be applied similarly to assemble the developed dynamic stiffness matrices of both the machine and its supporting beam structures. A beam-like raft carrying a machine is designed to illustrate the accuracy of the proposed method in numerical simulation, where the differences brought by three-DOF modeling in vibration transmission analysis are discussed as well. This work would provide a novel and easy-to-use alternative to the existing mobility method and finite element method due to low discretization requirements, high efficiency, and high accuracy.
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Liao, Xia, Danhui Dan, Fei Han, and Rui Zhao. "Research on the Dynamic Characteristics of the Double Slings System with Elastic Connection Considering Boundary Conditions." Mathematics 10, no. 17 (September 1, 2022): 3129. http://dx.doi.org/10.3390/math10173129.
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As the length of single sling increases, double slings with transverse connections are gradually becoming one of the effective measures to control the undesirable vibration of single slings. In the analysis of the dynamic characteristics of the double sling system, this paper firstly deduces the dynamic stiffness matrix of the elastically connected double sling system by the dynamic stiffness method (DSM), solves the frequency equation evolved from the dynamic stiffness matrix by using the Wittrick-Williams (W-W) algorithm, and obtains the systematic analysis and calculation of the dynamic characteristics of the double sling system under arbitrary boundary conditions. Secondly, a complete and accurate analysis method of the dynamic characteristics of the double sling system is obtained by comprehensively considering the bending stiffness and boundary conditions of the sling, and the accuracy of the calculation can be verified by the actual measurement data. Finally, the best installation position and quantity of transverse sling clamps in the double sling system are obtained by the parametric analysis of transverse sling clamps. The analysis of this paper will provide a theoretical basis for the design and optimization of slings, and further promote the wide application of the double sling system.
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Chauhan, Manish, Pawan Mishra, Sarvagya Dwivedi, Minvydas Ragulskis, Rafał Burdzik, and Vinayak Ranjan. "Development of the Dynamic Stiffness Method for the Out-of-Plane Natural Vibration of an Orthotropic Plate." Applied Sciences 12, no. 11 (June 5, 2022): 5733. http://dx.doi.org/10.3390/app12115733.
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In this present paper, the dynamic stiffness method (DSM) was formulated to investigate the out-of-plane natural vibration of a thin orthotropic plate using the classical plate theory (CPT). Hamilton’s principle was implemented to derive the governing differential equation of motion for free vibration of the orthotropic plate for Levy-type boundary conditions. The Wittrick–Williams (W–W) algorithm was used as a solution technique to compute the natural frequencies of a thin orthotropic plate for different boundary conditions, aspect ratios, thickness ratios, and modulus ratios. The obtained results are compared with the results by the finite element method using commercial software (ANSYS and those available) in the published literature. The presented results by the dynamic stiffness method can be used as a benchmark solution to compare the natural frequencies of orthotropic plates.
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Badr, Atef, and Aristides G. Karlaftis. "Using the Asphalt Pavement Dynamic Stiffness Modulus in Assessing Falling Weight Deflectometer Test Results." Advanced Materials Research 685 (April 2013): 233–39. http://dx.doi.org/10.4028/www.scientific.net/amr.685.233.
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Assessing pavement quality has attracted significant interest in the literature. Despite this interest, what has been commonly overlooked in pavement research are cost and time related constraints imposed by the various most frequently employed methods. This study develops an approach for the rapid assessment of pavement structural quality that can be readily implemented in the field and can lead to limiting testing budget. Assessment is based on the Dynamic Stiffness Modulus (DSM) that has been recognized as a fairly accurate indicator of pavement quality. Results indicate that a DSM value of less than 0.80 indicates poor pavement conditions and a value higher than 1.20 indicates good pavement structural conditions. Also, the DSM shows a relatively good correlation with the asphalt pavement modulus in flexible pavements and, since the DSM can be easily produced in the field during testing, it can also be used to ascertain the amount of FWD testing required at each testing section.
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Ter-Martirosyan, Armen, Vitalii Sidorov, and Evgeny Sobolev. "Dynamic Properties of Soil Cements for Numerical Modelling of the Foundation’s Basis Transformed under the Technology of Deep Soil Mixing: A Determination Method." Buildings 12, no. 7 (July 16, 2022): 1028. http://dx.doi.org/10.3390/buildings12071028.
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This research investigates the mechanical properties of soil-cement specimens ranging from ultrasmall to large values of shear strain at dynamic loading. The nonlinear behavior of soil cement exposed to dynamic loading in a wide range of changing shear strains was examined on the basis of two mechanical models. All soil-cement specimens were collected from under an existing building and modified with deep soil mixing (DSM.). Soil-cement samples were examined using low-amplitude oscillations in the resonant column and the dynamic triaxial compression method. Additionally, the stress–strain state for modified footings exposed to dynamic loading, and the approximation of soil stiffness and damping coefficient was analyzed. Dependencies on the basis of the resilient elastic models of Ramberg–Osgood and Hardin–Drnevich are proposed for application. Results reveal that the empirical graphs of the dependency soil stiffness–shear strain based on various methods exhibited the distinctive S-shape of decreased stiffness. The stiffness of the soil cement was reduced by 50% of the maximal value at shear strains of the 10−3 decimal order. The method presented in this study enables the drawing of stiffness change and damping–shear strain dependency where the range of shear strains changes from ultrasmall to large strains. The normalized modulus of shearing and the damping coefficient on shear strains for soil cement could be obtained under the proposed method. This method can be used for the preliminary calculations of structures on the footing modified by mathematical modelling or when field research data from site investigation are not available.
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Gaber, Omar, and Seyed M. Hashemi. "On the Free Vibration Modeling of Spindle Systems: A Calibrated Dynamic Stiffness Matrix." Shock and Vibration 2014 (2014): 1–10. http://dx.doi.org/10.1155/2014/787518.
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The effect of bearings on the vibrational behavior of machine tool spindles is investigated. This is done through the development of a calibrated dynamic stiffness matrix (CDSM) method, where the bearings flexibility is represented by massless linear spring elements with tuneable stiffness. A dedicated MATLAB code is written to develop and to assemble the element stiffness matrices for the system’s multiple components and to apply the boundary conditions. The developed method is applied to an illustrative example of spindle system. When the spindle bearings are modeled as simply supported boundary conditions, the DSM model results in a fundamental frequency much higher than the system’s nominal value. The simply supported boundary conditions are then replaced by linear spring elements, and the spring constants are adjusted such that the resulting calibrated CDSM model leads to the nominal fundamental frequency of the spindle system. The spindle frequency results are also validated against the experimental data. The proposed method can be effectively applied to predict the vibration characteristics of spindle systems supported by bearings.
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Thinh, Tran Ich, Nguyen Manh Cuong, and Vu Quoc Hien. "Dynamic stiffness method for free vibrations analysis of partial fluid-filled orthotropic circular cylindrical shells." Vietnam Journal of Mechanics 37, no. 1 (February 28, 2015): 43–56. http://dx.doi.org/10.15625/0866-7136/37/1/5508.
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Free vibrations of partial fluid-filled orthotropic circular cylindrical shells are investigated using the Dynamic Stiffness Method (DSM) or Continuous Element Method (CEM) based on theFirst Order Shear Deformation Theory (FSDT) and non-viscous incompressible fluid equations. Numerical examples are given for analyzing natural frequencies and harmonic responses of cylindrical shells partially and completely filled with fluid under various boundary conditions. The vibration frequencies for different filling ratios of cylindrical shells are obtained and compared with existing experimental and theoretical results which indicate that the fluid filling can reduce significantly the natural frequencies of studiedcylindrical shells. Detailed parametric analysis is carried out to show the effects of some geometrical and material parameters on the natural frequencies of orthotropic cylindrical shells. The advantages of this current solution consist in fast convergence, low computational cost and high precision validating for all frequency ranges.
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Ali, Md Imran, and Mohammad Sikandar Azam. "Dynamic Stiffness Formulation for Out-of-Plane Natural Vibration of Elastically Supported Functionally Graded Plates." International Journal of Structural Stability and Dynamics 21, no. 05 (February 25, 2021): 2150062. http://dx.doi.org/10.1142/s0219455421500620.
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In this paper, the natural vibration characteristics of elastically supported functionally graded material plate are investigated using the dynamic stiffness method (DSM). Power-law functionally graded (P-FG) plate, the material properties of which vary smoothly along the thickness direction following the power-law function, that has been used for the analysis. Classical plate theory and Hamilton’s principle are used for deriving the governing differential equation of motion and associated edge conditions for P-FG plate supported by elastic foundation. During the formulation of dynamic stiffness (DS) matrix, the concepts of rotary inertia and neutral surface are implemented. Wittrick–Williams (W-W) algorithm is used as a solving technique for the DS matrix to compute eigenvalues. The results thus obtained by DSM for the isotropic, P-FG plate, and the P-FG plate with elastic foundation compare well with published results that are based on different analytical and numerical methods. The comparisons indicate that this approach is very accurate. Furthermore, results are provided for elastically supported P-FG plate under four different considerations in order to see the differences in frequencies with the inclusion or exclusion of neutral surface and/or rotary inertia. It is noticed that the inclusion of rotary inertia and neutral surface influences the eigenvalues of P-FG plate, and that cannot be discounted. The study also examines the influence of plate geometry, material gradient index, edge conditions, and elastic foundation modulus on the natural frequency of P-FG plate.
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Otsubo, Masahide, Troyee Tanu Dutta, Manushak Durgalian, Reiko Kuwano, and Catherine O'Sullivan. "Particle-scale insight into transitional behaviour of gap-graded materials – small-strain stiffness and frequency response." E3S Web of Conferences 92 (2019): 14006. http://dx.doi.org/10.1051/e3sconf/20199214006.
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This study aims to develop a fundamental understanding of the role of fine particles on the small-strain stiffness of gap-graded granular soils. Stiffness was measured using cyclic triaxial probes, which give a measure of static stiffness, and dynamic wave propagation data, from which the dynamic stiffness can be measured. Assemblies of loosely packed spherical particles were considered. In the laboratory, local deformation transducers were used to measure the static stiffness, while the dynamic stiffness was calculated from stress wave velocities, measured using planar piezoelectric elements. To relate the particle-scale responses to the overall soil stiffness, complementary discrete element method (DEM) simulations were performed in which both static and dynamic stiffnesses were measured. Both the laboratory and the DEM data indicate that at low fines contents (< 30%) the stiffness decreases with increasing fines content. When the fines content increases from 30% to 35% there is a sharp increase in stiffness with increasing fines content; this is understood to mark the transition point at which the fines start to contribute significantly to the overall behaviour. Analyses of the frequency domain response of shear wave signals revealed that the lowpass frequency increases significantly at this transition point. This observation can be used to develop experimental interpretation protocols to assess to what extent fines are contributing to the overall soil stiffness.
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Bozyigit, Baran. "Earthquake response of linear-elastic arch-frames using exact curved beam formulations." Engineering Computations 39, no. 2 (October 28, 2021): 792–812. http://dx.doi.org/10.1108/ec-05-2021-0281.
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PurposeThis study aims to obtain earthquake responses of linear-elastic multi-span arch-frames by using exact curved beam formulations. For this purpose, the dynamic stiffness method (DSM) which uses exact mode shapes is applied to a three-span arch-frame considering axial extensibility, shear deformation and rotational inertia for both columns and curved beams. Using exact free vibration properties obtained from the DSM approach, the arch-frame model is simplified into an equivalent single degree of freedom (SDOF) system to perform earthquake response analysis.Design/methodology/approachThe dynamic stiffness formulations of curved beams for free vibrations are validated by using the experimental data in the literature. The free vibrations of the arch-frame model are investigated for various span lengths, opening angle and column dimensions to observe their effects on the dynamic behaviour. The calculated natural frequencies via the DSM are presented in comparison with the results of the finite element method (FEM). The mode shapes are presented. The earthquake responses are calculated from the modal equation by using Runge-Kutta algorithm.FindingsThe displacement, base shear, acceleration and internal force time-histories that are obtained from the proposed approach are compared to the results of the finite element approach where a very good agreement is observed. For various span length, opening angle and column dimension values, the displacement and base shear time-histories of the arch-frame are presented. The results show that the proposed approach can be used as an effective tool to calculate earthquake responses of frame structures having curved beam elements.Originality/valueThe earthquake response of arch-frames consisting of curved beams and straight columns using exact formulations is obtained for the first time according to the best of the author’s knowledge. The DSM, which uses exact mode shapes and provides accurate free vibration analysis results considering each structural members as one element, is applied. The complicated structural system is simplified into an equivalent SDOF system using exact mode shapes obtained from the DSM and earthquake responses are calculated by solving the modal equation. The proposed approach is an important alternative to classical FEM for earthquake response analysis of frame structures having curved members.
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Chen, Y., J. Zhang, H. Zhang, X. Li, and J. Zhou. "Extraction of Natural Frequencies and Mode Shapes of Rotating Beams by Variational Iteration Method." International Journal of Structural Stability and Dynamics 16, no. 03 (March 3, 2016): 1450106. http://dx.doi.org/10.1142/s0219455414501065.
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Flapwise flexural vibration of rotating beams has been extensively studied since the 1970s. Existing methods for solving the aforementioned vibration problem range from the conventional finite element method to variable-order finite element method, Frobenius method, differential transformation method and dynamic stiffness method (DSM). Although various approximation methods are available, most of these methods are based on perturbation or discretization of the governing equation, often leading to tedious calculations. This paper re-examines flapwise flexural vibration of rotating beams using the method of variational iteration, which is relatively new and capable of providing accurate solutions for eigenvalue problems. The extracted natural frequencies and mode shapes for sample rotating beams with various rotational speeds and hub radii are compared with existing results that were published in the open literature.
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Pourashraf, Talieh, Philip Bonello, and Jason Truong. "Analytical and Experimental Investigation of a Curved Piezoelectric Energy Harvester." Sensors 22, no. 6 (March 12, 2022): 2207. http://dx.doi.org/10.3390/s22062207.
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Piezoelectric energy harvesters have traditionally taken the form of base excited cantilevers. However, there is a growing body of research into the use of curved piezoelectric transducers for energy harvesting. The novel contribution of this paper is an analytical model of a piezoelectric energy harvesting curved beam based on the dynamic stiffness method (DSM) and its application to predict the measured output of a novel design of energy harvester that uses commercial curved transducers (THUNDER TH-7R). The DSM predictions are also verified against results from commercial finite element (FE) software. The validated results illustrate the resonance shift and shunt damping arising from the electrical effect. The magnitude, phase, Nyquist plots, and resonance frequency shift estimates from DSM and FE are all in satisfactory agreement. However, DSM has the advantage of having significantly fewer elements and is sufficiently accurate for commercial curved transducers used in applications where beam-like vibration is the predominant mode of vibration.
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Li, Shang Ming. "Transient Analysis of Dam-Reservoir Interaction Based on Dynamic Stiffness of SBFEM." Advanced Materials Research 378-379 (October 2011): 213–17. http://dx.doi.org/10.4028/www.scientific.net/amr.378-379.213.
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The scaled boundary finite element method (SBFEM) was extended to solve dam-reservoir interaction problems in the time domain and a dynamic stiffness used in the SBFEM of semi-infinite reservoir in the time domain was proposed, which was evaluated by the Bessel function. Based on the dynamic stiffness, transient responses subjected to horizontal ground motions were analyzed through coupling the SBFEM and finite element method (FEM). A dam was modeled by FEM, while the whole fluid in reservoir was modeled by the SBFEM alone or a combination of FEM and SBFEM. Two benchmark examples were considered to check the accuracy of the dynamic stiffness. Results were compared with those from analytical or substructure methods and good agreements were found.
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Le, Nam Bich, Cuong Manh Nguyen, and Thinh Ich Tran. "CONTINUOUS ELEMENT FORMULATIONS FOR COMPOSITE RING-STIFFENED CYLINDRICAL SHELLS." Vietnam Journal of Science and Technology 56, no. 4 (August 6, 2018): 515. http://dx.doi.org/10.15625/2525-2518/56/4/10987.
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This research studies the free vibration of composite ring-stiffened cylindrical shells by the continuous element method (CEM). The dynamic stiffness matrix (DSM) of the investigated structure has been constructed based on the analytical solutions of the governing equations of motion for composite cylindrical shells and annular plates. By applying the powerful assembly procedure of continuous elements method, natural frequencies and harmonic responses of composite ring-stiffened cylindrical shells have been obtained. In addition, the proposed model allows extracting exactly ring-stiffener vibration modes by choosing appropriate points of response. Numerical examples have confirmed many advantages of the developed model.
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Gee, Aaron, and Seyed M. Hashemi. "Undamped Free Vibration Analysis of Functionally Graded Beams: A Dynamic Finite Element Approach." Applied Mechanics 3, no. 4 (October 7, 2022): 1223–39. http://dx.doi.org/10.3390/applmech3040070.
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A Dynamic Finite Element (DFE) method for coupled axial–flexural undamped free vibration analysis of functionally graded beams is developed and subsequently used to investigate the system’s natural frequencies and mode shapes. The formulation is based on the Euler–Bernoulli beam theory and material grading is assumed to follow a power law variation through the thickness direction. Using the closed-form solutions to the uncoupled segments of the system’s governing differential equations as the basis functions of approximation space, the dynamic, frequency-dependent, trigonometric interpolation functions are developed. The interpolation functions are used with the weighted residual method to develop the DFE of the system. The resulting nonlinear eigenvalue problem is then solved to determine the coupled natural frequencies. Example elements using DFE, Finite Element Method (FEM) and the Dynamic Stiffness Method (DSM) are implemented in MATLAB for testing, verification, and validation. Good agreement was observed and the DFE formulation exhibited superior convergence performance compared to the FEM.
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Dan, Danhui, Xia Liao, and Fei Han. "Research on the Dynamic Characteristics of Cables Considering the Constraints at Both Ends of the Cables." Applied Sciences 12, no. 4 (February 17, 2022): 2100. http://dx.doi.org/10.3390/app12042100.
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Suspension bridges and arch bridges are important structural forms of bridges in which the cables are the main load-bearing members. The study of dynamic characteristics of the cable is of great significance to the design and operation and maintenance of suspension bridges and arch bridges. Firstly, this paper derives the cable frequency equation considering the bending stiffness under arbitrary boundary conditions from the dynamic stiffness method (DSM), and gives the calculation method of cable vibration modal frequency based on the W–W algorithm. Secondly, on this basis, the cable boundary condition coefficients and stiffness ratios are introduced to reflect the constraint strength of the main cable and stiffening beam on the cable, so as to study the influence law of these boundary conditions on the cable modal frequency, and then determine the actual cable boundary conditions of this kind of bridge. Finally, the boundary condition coefficients determined in this paper and the relevant parameters of the cables are inversely used to determine the boundary conditions of the actual bridge cables, and a simple method suitable for determining the boundary conditions of the cables in practical engineering is discussed, i.e., the theoretical basis for determining the boundary conditions of the cables through the relevant parameters of the cables, and the practical discussion of the theory is verified through the actual bridge cables. This study provides a reference for further theoretical analysis of cables, a theoretical basis for calculation of actual bridge cables, boundary conditions for in-depth study of dynamic characteristics of cables, and guides the design, operation, and maintenance of cables.
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Wang, Yingjie, Zuzana Dimitrovová, and Jong-Dar Yau. "Dynamic response of a vehicle with flexible car body moving on a ballasted track." MATEC Web of Conferences 211 (2018): 11003. http://dx.doi.org/10.1051/matecconf/201821111003.
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In this study, the dynamic response of a vehicle with flexible car body moving on a ballasted track is investigated. The vehicle/track interaction model is divided into two sub-systems, namely the vehicle and the ballasted track sub-system. The vehicle sub-system is composed by one flexible car body, two bogies and four wheel sets. The car body is created using flexible multibody dynamics. The ballasted track consists of rail, sleeper, ballast and sub-grade. For its representation the simplified 2D discrete support model (DSM) is used and modelled by finite elements. The connection between the two sub-systems, i.e. between the moving wheels and the track is ensured by a linearized Hertzian spring. The dynamic response of the vehicle/track system is computed by the Newmark-β integration method. The effect of the car body flexibility on the dynamic response of this system is analyzed and evaluated based on the maximum car center acceleration. It is concluded that the increase in flexural stiffness of the car body can lead to a notable decrease of its maximum acceleration.
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Yasuda, N., N. Ohta, and A. Nakamura. "Dynamic deformation characteristics of undisturbed riverbed gravels." Canadian Geotechnical Journal 33, no. 2 (May 8, 1996): 237–49. http://dx.doi.org/10.1139/t96-003.
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The strength and deformation characteristics of undisturbed specimens measured by large-scale triaxial tests were compared with those of reconstituted specimens to evaluate the stiffness of natural ground. The undisturbed specimens were sampled from the riverbed gravel foundation of an embankment dam using the freezing sampling method with liquid nitrogen. The validity of the results from the undisturbed specimens was evaluated by comparing the stiffness of the natural ground using P- and S-wave logging (PS logging). The dynamic deformation characteristics (stiffness) of undisturbed specimens are larger than those of reconstitued specimens. Key words: shear modulus, damping ratio, gravel, laboratory test.
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Hong, Jinpyo, Seokhoon Oh, and Eunsang Im. "Stiffness and Cavity Test of Concrete Face Based on Non-Destructive Elastic Investigation." Sustainability 10, no. 12 (November 24, 2018): 4389. http://dx.doi.org/10.3390/su10124389.
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A non-destructive testing (NDT) method was used in a concrete face rockfill dam (CFRD) to identify the condition of the concrete face slab and detect any existing cavities between the concrete face slab and the underlying support layer. The NDT for the concrete face slab was conducted using the impulse response (IR) method and the electrical resistivity tomography (ERT) method with the application of non-destructive electrodes. Information regarding the dynamic stiffness and average mobility of the concrete was obtained based on the mobility-frequency of the IR method, and cavity detection under the plate structures was analyzed using the two-dimensional (2D) electrical resistivity section of the ERT method. The results of the IR method showed that zones with low dynamic stiffness and high average mobility were expected to be found in concrete of poor quality and in cavities beneath the concrete face slab. The results of the ERT method showed that zones with high resistivity were expected to be cavities between the concrete face slab and the underlying support layer. As a result, the tendency toward low dynamic stiffness, high average mobility, and high resistivity in both methods implies unstable concrete conditions and the possible occurrence of a cavity. The results of the two methods also showed a good correlation, and it was confirmed that the NDT method was reliable in terms of cavity estimation.
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Kiss, Róbert, and Attila Szilágyi. "Analysis of the dynamic behaviour of the CNC machine centre by FEM." Design of Machines and Structures 9, no. 1 (2019): 24–28. http://dx.doi.org/10.32972/dms.2019.003.
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This note is the first part of an extended research-analysis work, where our aim is to summarize the concepts of the methods and measurements, which we will present in the later articles. The research is focusing on the dynamic behavior of the DMU 40 5-axis CNC machine center, which can be found in the workshop of the Department of Machine Tools. This means that we would like to determine the magnitude of the dynamic stiffness of the machine tool, by calculating the value of the natural frequencies by final element method (analytically, and with software), and with the help of an experimental test.
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Kiss, Róbert, and Attila Szilágyi. "Analysis of DMU40 machine centre by finite degrees of freedom." Design of Machines and Structures 10, no. 2 (2020): 49–53. http://dx.doi.org/10.32972/dms.2020.013.
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This article is part of a longer research-analytical work, because it outlines the results and conclusions of the study according to the main topic of the research and the applies method. The central theme of the research is the dynamic stiffness of machine tools and the various methods for their determination. The first such (finite element) method is modal analysis, which allows for an analytical test. The purpose of this article is to approach this study from the practical side through a specific example.
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Alaimo, A., A. Milazzo, and C. Orlando. "On the dynamic behavior of piezoelectric active repair by the boundary element method." Journal of Intelligent Material Systems and Structures 22, no. 18 (October 23, 2011): 2137–46. http://dx.doi.org/10.1177/1045389x11425281.
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The dynamic behavior of piezoelectric active repair bonded on cracked structures is analyzed in this article. The boundary element code used to perform the simulations is implemented in the framework of piezoelectricity in order to model the coupling between the elastic and the electric fields, which represents the most important feature of piezoelectric media. The fracture mechanics problem, i.e. the crack, as well as the bonding layer between the host structure and the active patch is modeled by means of the multidomain technique provided with an interface spring model. More particularly, the spring interface model allows considering the bonding layer as a zero-thickness elastic ply characterized by normal and tangential stiffness constants. The crack is also modeled as an elastic interface characterized by vanishing stiffness. The dual reciprocity method (DRM) has been used in the present time-dependent application for the approximation of the domain inertia terms. Numerical analyses have been carried out in order to characterize the dynamic repairing mechanism of the assembled structure by means of the computation of the dynamic stress intensity factors and discussions are presented to highlight the effect of the inertial forces on the fracture mechanics behavior of the overall assembled structure.
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Kiss, Róbert, and Attila Szilágyi. "Analysis of DMU40 machine centre by CAE software." Design of Machines and Structures 10, no. 2 (2020): 54–58. http://dx.doi.org/10.32972/dms.2020.014.
Full textAbstract:
This article is part of a longer research-analytical work, because it outlines the results and conclusions of the study according to the main topic of the research and the applied method. The central theme of the research is the dynamic stiffness of machine tools and the various methods for their determination. After analytical testing, we will deal with another method, because we also use CAE software (ANSYS Workbench R19.1) to perform previous tests in the form of simulations. The results obtained are compared with the values previously determined analytically.
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Qi, Nian, and Ji Hong Ye. "Nonlinear Dynamic Analysis of Space Frame Structures by Discrete Element Method." Applied Mechanics and Materials 638-640 (September 2014): 1716–19. http://dx.doi.org/10.4028/www.scientific.net/amm.638-640.1716.
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This document explores the possibility of the discrete element method (DEM) being applied in nonlinear dynamic analysis of space frame structures. The method models the analyzed object to be composed by finite particles and the Newton’s second law is applied to describe each particle’s motion. The parallel-bond model is adopted during the calculation of internal force and moment arising from the deformation. The procedure of analysis is vastly simple, accurate and versatile. Numerical examples are given to demonstrate the accuracy and applicability of this method in handling the large deflection and dynamic behaviour of space frame structures. Besides, the method does not need to form stiffness matrix or iterations, so it is more advantageous than traditional nonlinear finite element method.
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Mahmood, Faisal, Seyed M. Hashemi, and Hekmat Alighanbari. "Free Vibration Analysis of a Reconfigurable Modular Morphing Wing." Aerospace 9, no. 10 (September 21, 2022): 532. http://dx.doi.org/10.3390/aerospace9100532.
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Aircraft experience various phases during each flight. Optimal performance, without compromise, during various phases can be achieved through adaptability in the wing design. Morphing wing design encompasses most, if not all, the flight conditions variations, and can respond interactively. In the present work, the dynamic characteristics of a reconfigurable modular morphing wing of two topological architectures, developed in-house by a research group at Toronto Metropolitan University (formerly Ryerso University), were investigated. This modular morphing wing, developed based on the idea of a parallel robot, consists of a number of structural elements connected to each other and to the wing ribs through eye-bolt joints. Euler–Bernoulli and Timoshenko bending beam theories, in conjunction with Finite Element Analysis, were exploited. Free vibration of unmorphed (Original) and morphed configurations subjected to spanwise extensions were studied. The results of systems’ free vibration analyses were validated against those obtained from Ansys and Dynamic Stiffness Matrix (DSM) method. The effect of various spanwise extensions, as well as topology on system’s natural frequencies, was also studied and reported on.
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Kiss, Róbert, and Attila Szilágyi. "Analysis of DMU40 machine centre by vibration measurement." Design of Machines and Structures 10, no. 2 (2020): 59–64. http://dx.doi.org/10.32972/dms.2020.015.
Full textAbstract:
This article is part of a longer research-analytical work, because it outlines the results and conclusions of the study according to the main topic of the research and the applied method. The central theme of the research is the dynamic stiffness of machine tools and the various methods for their determination. Following analytical analysis the machine tool natural frequencies were determined using a finite element software (ANSYS Workbench R19.1), which we now approach from a practical point of view, that is determined in the workshop by measurements. The results obtained are compared for each of the three methods.
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Zhang, Jing, Ying Lv, and Lianhe Li. "Dynamic Instability of Functionally Graded Graphene Platelet-Reinforced Porous Beams on an Elastic Foundation in a Thermal Environment." Nanomaterials 12, no. 22 (November 21, 2022): 4098. http://dx.doi.org/10.3390/nano12224098.
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Under thermal environment and axial forces, the dynamic instability of functionally graded graphene platelet (GPLs)-reinforced porous beams on an elastic foundation is investigated. Three modes of porosity distributions and GPL patterns are considered. The governing equations are given by the Hamilton principle. On the basis of the differential quadrature method (DQM), the governing equations are changed into Mathieu–Hill equations, and the main unstable regions of the porous composite beams are studied by the Bolotin method. Thermal buckling and thermo-mechanical vibration problems are also studied. The effects of porosity coefficients and GPL weight fraction, dispersion pattern, initial thermal loading, slenderness ratio, geometry and size, boundary conditions, and foundation stiffness are discussed. The conclusions show that an elastic foundation has an obvious enhancement effect on thermal buckling, free vibration, and dynamic instability, which improves the stiffness of the beam.
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Tsai, Pei Hsun, and Kang Nan Chen. "Application of MASW Method for Evaluating Dynamic Properties of Lu-Liao-His Earth Dam." Applied Mechanics and Materials 105-107 (September 2011): 216–19. http://dx.doi.org/10.4028/www.scientific.net/amm.105-107.216.
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In the paper the shear wave velocity and Poisson’s ratio profile are studied using the MASW test. Slant stacking was adopted in experimental dispersion curve constructing. Theoretical dispersion curve can be constructed by thin layer stiffness matrix method. A real-parameter genetic algorithm is required to minimize the error between the theoretical and experimental dispersion curves. Test results show that spectrum using slant stacking shows the fundamental mode of Rayleigh wave in the frequency range from 15 Hz to 50Hz. To reduce the error of experimental and theoretical dispersion curve using real-parameter genetic algorithm is feasible. The results also show that the strata of Lu-Liao-His Earth Dam can be modeled as 3 soil layers with an underlying half space.
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Zhu, Ya Lin, Xian Jing Kong, and De Gao Zou. "Dynamic Elastic-Plastic Analysis of Reinforcement Geogrids Applied in High Earth-Rockfilled Dam Slope." Advanced Materials Research 243-249 (May 2011): 4520–23. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.4520.
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Considering the dynamic response of high earth-rockfilled dam, dynamic elasto-plastic analysis method for dam slope reinforcement with geogrids was set up. Based on this model, the paper analyzed the deformation and failure mechanism of dam slope, as well as the effect of connection, the length, the spacing and the stiffness of geogrid on dam with deformation. The results show that geogrids with high elastic modulus and proper extensibility will apparently reduce the deformation and imporve the stability of the dam slope. In the case of high dam slope, the reinforcement length of geogrids is supposed to be 2a (a is the slip surface length), and the spacing is 2m.
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Lin, Peng, Wenwei Zheng, Bo Huang, and Haichao Zhang. "Seismic Fortification Analysis of the Guoduo Gravity Dam in Tibet, China." Shock and Vibration 2015 (2015): 1–15. http://dx.doi.org/10.1155/2015/396124.
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The primary aim of this research was to analyze the seismic performance of the Guoduo gravity dam. A nonlinear FEM method was implemented to study the deformation, stress, and overall stability of dam under both static and dynamic loading conditions, including both normal and overloading conditions. A dam seismic failure risk control method is proposed based on the cracking mechanism induced by the dynamic load to ensure dam safety and stability. Numerical simulation revealed that (1) under normal static and dynamic loading the symmetry of the displacement distributions is good, showing that the dam abutments and riverbed foundation have good overall stiffness. The stress distribution is a safe one for operation under both normal water loading and seismic loading. (2) Attention should be paid to the reinforcement design of outlets of the diversion dam monoliths, and enhance the capability of sustaining that tensile stress of dam monoliths. (3) The shape of the dam profile has a significant effect on the dynamic response of the dam. (4) By employing the “overload safety factor method,” the overall seismic fortification is as follows:K1=1.5,K2=2~3, andK3=3~4.
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Yang, Yilin, and Jinzhao Li. "SPH-FE-Based Numerical Simulation on Dynamic Characteristics of Structure under Water Waves." Journal of Marine Science and Engineering 8, no. 9 (August 20, 2020): 630. http://dx.doi.org/10.3390/jmse8090630.
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Offshore structures are prone to produce a dynamic response under the effect of large wave load. In this paper, the smoothed particle hydrodynamics coupled with finite element (SPH-FE) method is used to investigate the dynamic characteristics of structure induced by the water waves. The dam break model is assumed to generate water wave. Firstly, the parameter of particle spacing included in the SPH method is examined and the appropriate value is proposed. Subsequently, the present numerical model is validated by comparing with the available results from the literature. Furthermore, the influence of several parameters on the wave load of the structure and the induced dynamic characteristics is studied, including the water column height, the distance between the water column and structure, and the structure stiffness. The results show that the amplification of the wave load on the bottom of structure is greater than that on the upper part of the structure. The increase of structure stiffness results in a decrease in the displacement at the top of structure, but an increase in the hydrodynamic force at the bottom of structure.
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An, Chao, Chao Yang, Changchuan Xie, and Yang Meng. "Gust Load Alleviation including Geometric Nonlinearities Based on Dynamic Linearization of Structural ROM." International Journal of Aerospace Engineering 2019 (May 12, 2019): 1–20. http://dx.doi.org/10.1155/2019/3207912.
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This paper describes a framework for an active control technique applied to gust load alleviation (GLA) of a flexible wing, including geometric nonlinearities. Nonlinear structure reduced order model (ROM) and nonplanar double-lattice method (DLM) are used for structural and aerodynamic modeling. The structural modeling method presented herein describes stiffness nonlinearities in polynomial formulation. Nonlinear stiffness can be derived by stepwise regression. Inertia terms are constant with linear approximation. Boundary conditions and kernel functions in the nonplanar DLM are determined by structural deformation to reflect a nonlinear effect. However, the governing equation is still linear. A state-space equation is established in a dynamic linearized system around the prescribed static equilibrium state after nonlinear static aeroelastic analysis. Gust response analysis can be conducted subsequently. For GLA analysis, a classic proportional-integral-derivative (PID) controller treats a servo as an actuator and acceleration as the feedback signal. Moreover, a wind tunnel test has been completed and the effectiveness of the control technology is validated. A remote-controlled (RC) model servo is chosen in the wind tunnel test. Numerical simulation results of gust response analysis reach agreement with test results. Furthermore, the control system gives GLA efficacy of vertical acceleration and root bending moment with the reduction rate being over 20%. The method described in this paper is suitable for gust response analysis and control strategy design for large flexible wings.
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SALEH, S., and S. P. G. MADABHUSHI. "RESPONSE OF CONCRETE DAMS ON RIGID AND SOIL FOUNDATIONS UNDER EARTHQUAKE LOADING." Journal of Earthquake and Tsunami 04, no. 03 (September 2010): 251–68. http://dx.doi.org/10.1142/s1793431110000820.
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Dynamic response of dams under earthquake loading depends on their foundation stiffness. Additional hydrodynamic pressures are generated not only by the ground motions but also due to the dynamic response of the dam to the ground motions. The magnitude and distribution of hydrodynamic pressures vary and these effect the deformation of dam which in turn influences the pressure. This paper aims at investigating the effect of dam–foundation interaction on the dynamic response and consequent development of hydrodynamic pressure on dam face using dynamic centrifuge modelling technique. From a series of centrifuge tests it was found that the inclusion of a flexible foundation significantly reduces the dynamic response of the dam. Significant correlation was also observed between the dynamic response of dams and the hydrodynamic pressures developed on their faces. Comparisons with theoretical hydrodynamic pressures show that Westergaard's equation gives a conservative estimation of hydrodynamic pressures during most nonresonant vibrations. Comparison with Chopra's method revealed that it severely underpredicts hydrodynamic pressures for low reservoir depths. However, it yields a reasonably good approximation of the hydrodynamic pressures for higher depth of reservoirs during nonresonant vibration.
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Saeed, Najmadeen, Ahmed Manguri, Marcin Szczepanski, and Robert Jankowski. "Non-Linear Analysis of Structures Utilizing Load-Discretization of Stiffness Matrix Method with Coordinate Update." Applied Sciences 12, no. 5 (February 25, 2022): 2394. http://dx.doi.org/10.3390/app12052394.
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This paper proposes a stiffness method based structural analysis algorithm for geometrically non-linear structures. In this study, the applied load on the joints has been discretized to a sequence of a few loadings applied. Each loading step produces incremental external nodal displacements, which are added to the corresponding coordinates to get a new geometrical shape of the structure. This process is iteratively repeated until the sum of the loading of all iterations matches the total initial applied loading. The size of the increments affects the technique’s accuracy, subsequently affecting the number of iterations. The configuration of non-linear geometrical structures is vital in the work; a slight change of the coordinates makes a considerable variation of nodal displacements. In this paper, three pin-jointed assemblies and a cantilever beam have been examined using the proposed technique; significantly reasonable outcomes emerged, compared to the non-linear approaches, such as Dynamic Relaxation Method (DRM) and Non-linear approach by Kwan. In a numerical sense, the dissimilarity between the results of the conventional Stiffness Matrix (SM) method and the non-linear method is about 228%, while the maximum discrepancy between the proposed approach and the non-linear methods is just above 15%.
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Arani, A. Tabatabaie, Ali Ghorbanpour Arani, and Reza Kolahchi. "Non-Newtonian pulsating blood flow-induced dynamic instability of visco-carotid artery within soft surrounding visco-tissue using differential cubature method." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 229, no. 16 (January 7, 2015): 3002–12. http://dx.doi.org/10.1177/0954406214566038.
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The high blood rate that often occurs in carotid arteries may play a role in artery failure and tortuosity which leads to blackouts, transitory ischemic attacks, and other diseases. However, dynamic analysis of carotid arteries conveying blood is lacking. The objective of this study was to present a biomechanical model for dynamic instability analysis of the embedded carotid arteries conveying pulsating blood flow. In order to present a realistic model, the carotid arteries and tissues are assumed viscoelastic using Kelvin–Voigt model. Carotid arteries are modeled as elastic cylindrical vessels based on Mindlin cylindrical shell theory (MCST). One of the main advantages of this study is considering the pulsating non-Newtonian nature of the blood flow using Carreau, Casson, and power law models. Applying energy method, Hamilton’s principle and differential cubature method (DCM), the dynamic instability region (DIR) of the visco-carotid arteries is obtained. The detailed parametric study is conducted, focusing on the combined effects of the elastic medium and non-Newtonian models on the dynamic instability of the visco-carotid arteries. It can be seen that with increasing the tissue stiffness, the natural frequency of visco-carotid arteries decreases. The current model provides a powerful tool for further experimental investigation about arterial tortuosity.
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Wang, Wei, and Xiaozu Su. "Algorithm of DRM with Kinetic Damping for Finite Element Static Solution of Strain-Softening Structures." Advances in Materials Science and Engineering 2017 (2017): 1–7. http://dx.doi.org/10.1155/2017/8060987.
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In order to deal with the divergence and instability due to the ill-posedness of the nonlinear finite element (FE) model of strain-softening structure in implicit static analysis, the dynamic relaxation method (DRM) was used with kinetic damping to solve the static increments in the incremental solution procedure so that the problem becomes well-posed. Moreover, in DRM there is no need to assemble and inverse the stiffness matrix as in implicit static analysis such that the associated computational cost is avoided. The ascending branch of static equilibrium path was solved by load increments, while the peak point and the descending branch were solved by displacement increments. Two numerical examples illustrated the effectiveness of such application of DRM in the FE analysis of static equilibrium path of strain-softening structures.
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Niu, Yaobin, Zhongwei Wang, and Weihua Zhang. "Nonlinear Thermal Flutter Analysis of Supersonic Composite Laminated Panels Using Differential Quadrature Method." International Journal of Structural Stability and Dynamics 14, no. 07 (July 24, 2014): 1450030. http://dx.doi.org/10.1142/s0219455414500308.
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In this paper, the differential quadrature method (DQM) was extended to deal with the nonlinear thermal flutter problem of supersonic composite laminated panel. Based on Hamilton's principle, the nonlinear thermal flutter model of composite panels was first established. The model adopted the von Karman large deflection plate theory for the geometrical nonlinearity, and the third order piston theory for the supersonic aerodynamic loads. Convergence and accuracy studies were carried out to verify the proposed approach. Finally, the nonlinear thermal flutter characteristics of a supersonic composite panel were studied. Uniform temperatures were first applied to the model in order to determine general heating effects on the stability of the composite panel. Owing to the varying structural stiffness of composite panels when subjected to thermal stresses, the thermal load reduced the frequency of composite panel, as well as the frequency interval between the first frequency and the second frequency; thereby hastening the flutter of composite panel. The nonlinear thermal flutter velocity ratio was decreased with respect to increasing temperature load for all aspect ratios. However, the influence of thermal loadings on flutter with various cross angles was different. Cases of unequal temperatures were considered. The average temperature load was kept constant which differs from the temperature gradient form of loading. The results show that the nonlinear thermal frequencies are affected in the presence of different temperature distributions. The changes in the temperature distribution have a slightly greater effect than changes in the average temperature. These effects due to temperature distribution changes do not have a substantial effect on the flutter dynamic pressure.
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Javanmard, Mehran, Reza Mottaghi, and S. M. Mir Mohammad Hosseini. "Investigating the Influence of Penetration Length of Cut-off Wall on its Dynamic Interaction with Core and Foundation of Earth Dam." Civil Engineering Journal 4, no. 12 (December 24, 2018): 3019. http://dx.doi.org/10.28991/cej-03091217.
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Seepage and flow of water in the soil is one of the most important issue and effective elements in designing embankment dams. One of the methods to control seepage in alluvial foundation of earth dams is to use a plastic concrete cutoff-wall. For better seepage control, the cutoff-wall extends inside the clayey core as the one of common method of connection of cut-off wall and the core. Due to the stiffness difference of the core material and cutoff-wall, and also due to geological situation, physical and mechanical properties of rock and foundation, interaction of core and foundation with cut-off wall in different static and dynamic load cases is very considerable. Failure of cut-off wall occurs in cut-off wall and core joint. So the study of their interaction, especially during an earthquake is very important. Karkheh dam cut-off wall with an area of about 150000 m2 is chosen for this study. FLAC software has been used to study the effect of cutoff-wall penetration length variation, inside the clay core of Karkheh earth dam under dynamic loading. In numerical analysis of Karkheh earth dam model, all construction stages and seepage through dam are modelled. The model is first calibrated according to the results obtained from the dam instrumentations. After calibrating, according to available seismic studies of region, a suitable acceleration was selected and applied to the model. In this research, in order to find the optimum length, the effect of 0, 5, 10, 15 and 20 meters penetration length of cut-off wall in aforementioned conditions has been investigated. The results of the numerical study showed that the horizontal displacement and the maximum shear strain in the cutoff-wall is occurred adjacent to the clay core and the interface of core and foundation is a critical point for the cut-off wall, and also the stress in cut off wall joint increases with the elongation of penetration depth of the wall.
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Schäfer, Dominik. "T-tail flutter simulations with regard to quadratic mode shape components." CEAS Aeronautical Journal 12, no. 3 (June 18, 2021): 621–32. http://dx.doi.org/10.1007/s13272-021-00524-8.
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AbstractIt is known that the dynamic aeroelastic stability of T-tails is dependent on the steady aerodynamic forces at aircraft trim condition. Accounting for this dependency in the flutter solution process involves correction methods for doublet lattice method (DLM) unsteady aerodynamics, enhanced DLM algorithms, unsteady vortex lattice methods (UVLM), or the use of CFD. However, the aerodynamic improvements along with a commonly applied modal approach with linear displacements results in spurious stiffness terms, which distort the flutter velocity prediction. Hence, a higher order structural approach with quadratic mode shape components is required for accurate flutter velocity prediction of T-tails. For the study of the effects of quadratic mode shape components on T-tail flutter, a generic tail configuration without sweep and taper is used. Euler based CFD simulations are applied involving a linearized frequency domain (LFD) approach to determine the generalized aerodynamic forces. These forces are obtained based on steady CFD computations at varying horizontal tail plane (HTP) incidence angles. The quadratic mode shape components of the fundamental structural modes for the vertical tail plane (VTP), i.e., out-of-plane bending and torsion, are received from nonlinear as well as linear finite element analyses. Modal coupling resulting solely from the extended modal representation of the structure and its influence on T-tail flutter is studied. The g-method is applied to solve for the flutter velocities and corresponding flutter mode shapes. The impact of the quadratic mode shape components is visualized in terms of flutter velocities in dependency of the HTP incidence angle and the static aerodynamic HTP loading.
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Caddemi, Salvatore, Ivo Calio, and Francesco Cannizzaro. "The dynamic stiffness matrix (DSM) of axially loaded multi-cracked frames." Mechanics Research Communications 84 (September 2017): 90–97. http://dx.doi.org/10.1016/j.mechrescom.2017.06.012.
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