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Numerical analysis of nonlinear dynamic behavior of earth dams

Babak EBRAHIMIAN

《结构与土木工程前沿（英文）》 2011年第5卷第1期页码 24-40 doi: 10.1007/s11709-010-0082-6

摘要： A numerical study is conducted to investigate the dynamic behavior of earth dams. The numerical investigation employs a fully nonlinear dynamic finite difference analysis incorporating a simple elastic perfectly plastic constitutive model to describe the stress-strain response of the soil and the Rayleigh damping to increase the level of hysteretic damping. The extended Masing rules are implemented into the constitutive model to explain more accurately the soil response under general cyclic loading. The soil stiffness and hysteretic damping change with loading history. The procedures for calibrating the constructed numerical model with centrifuge test data and also a real case history are explained. For the latter, the Long Valley (LV) earth dam subjected to the 1980 Mammoth Lake earthquake as a real case-history is analyzed and the obtained numerical results are compared with the real measurements at the site in both the time and frequency domains. Relatively good agreement is observed between computed and measured quantities. It seems that the Masing rules combined with a simple elasto-plastic model gives reasonable numerical predictions. Afterwards, a comprehensive parametric study is carried out to identify the effects of dam height, input motion characteristics, soil behavior, strength of the shell materials and dam reservoir condition on the dynamic response of earth dams. Three real earthquake records with different levels and peak acceleration values (PGAs) are used as input motions. The results show that the crest acceleration decreases when the dam height increases and no amplification is observed. Further, more inelastic behavior and more earthquake energy absorption are observed in higher dams.

关键词： earth dam numerical nonlinear response dynamic analysis earthquake dam height

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Nonlinear dynamic analysis of functionally graded carbon nanotube-reinforced composite plates using MISQ20

《结构与土木工程前沿（英文）》页码 1072-1085 doi: 10.1007/s11709-023-0951-4

摘要： The main objective of this study is to further extend the mixed integration smoothed quadrilateral element with 20 unknowns of displacement (MISQ20) to investigate the nonlinear dynamic responses of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) plates with four types of carbon nanotube distributions. The smooth finite element method is used to enhance the accuracy of the Q4 element and avoid shear locking without using any shear correction factors. This method yields accurate results even if the element exhibits a concave quadrilateral shape and reduces the error when the element meshing is rough. Additionally, the element stiffness matrix is established by integrating the boundary of the smoothing domains. The motion equation of the FG-CNTRC plates is solved by adapting the Newmark method combined with the Newton–Raphson algorithm. Subsequently, the calculation program is coded in the MATLAB software and verified by comparing it with other published solutions. Finally, the effects of the input parameters on the nonlinear vibration of the plates are investigated.

关键词： carbon nanotube MISQ20 FG-CNTRC plate nonlinear vibration nonlinear dynamic analysis SFEM

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Nonlinear analysis of cable structures using the dynamic relaxation method

Mohammad REZAIEE-PAJAND, Mohammad MOHAMMADI-KHATAMI

《结构与土木工程前沿（英文）》 2021年第15卷第1期页码 253-274 doi: 10.1007/s11709-020-0639-y

摘要： The analysis of cable structures is one of the most challenging problems for civil and mechanical engineers. Because they have highly nonlinear behavior, it is difficult to find solutions to these problems. Thus far, different assumptions and methods have been proposed to solve such structures. The dynamic relaxation method (DRM) is an explicit procedure for analyzing these types of structures. To utilize this scheme, investigators have suggested various stiffness matrices for a cable element. In this study, the efficiency and suitability of six well-known proposed matrices are assessed using the DRM. To achieve this goal, 16 numerical examples and two criteria, namely, the number of iterations and the analysis time, are employed. Based on a comprehensive comparison, the methods are ranked according to the two criteria. The numerical findings clearly reveal the best techniques. Moreover, a variety of benchmark problems are suggested by the authors for future studies of cable structures.

关键词： nonlinear analysis cable structure stiffness matrix dynamic relaxation method

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The study of hybrid model identification, computation analysis and fault location for nonlinear dynamic

XIE Hong, HE Yi-gang, ZENG Guan-da

《机械工程前沿（英文）》 2006年第1卷第2期页码 233-237 doi: 10.1007/s11465-006-0003-5

摘要： This paper presents the hybrid model identification for a class of nonlinear circuits and systems via a combination of the block-pulse function transform with the Volterra series. After discussing the method to establish the hybrid model and introducing the hybrid model identification, a set of relative formulas are derived for calculating the hybrid model and computing the Volterra series solution of nonlinear dynamic circuits and systems. In order to significantly reduce the computation cost for fault location, the paper presents a new fault diagnosis method based on multiple preset models that can be realized online. An example of identification simulation and fault diagnosis are given. Results show that the method has high accuracy and efficiency for fault location of nonlinear dynamic circuits and systems.

关键词： block-pulse function nonlinear multiple diagnosis combination

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Nonlinear dynamic analysis for elastic robotic arms

M. H. KORAYEM, H. N. RAHIMI

《机械工程前沿（英文）》 2011年第6卷第2期页码 219-228 doi: 10.1007/s11465-011-0218-y

摘要：

The aim of the paper is to analyze the nonlinear dynamics of robotic arms with elastic links and joints. The main contribution of the paper is the comparative assessment of assumed modes and finite element methods as more convenient approaches for computing the nonlinear dynamic of robotic systems. Numerical simulations comprising both methods are carried out and results are discussed. Hence, advantages and disadvantages of each method are illustrated. Then, adding the joint flexibility to the system is dealt with and the obtained model is demonstrated. Finally, a brief description of the optimal motion generation is presented and the simulation is carried out to investigate the role of robot dynamic modeling in the control of robots.

关键词： robotic arms elastic link elastic joint nonlinear dynamics optimal control

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A fast and accurate dynamic relaxation scheme

Mohammad REZAIEE-PAJAND, Mohammad MOHAMMADI-KHATAMI

《结构与土木工程前沿（英文）》 2019年第13卷第1期页码 176-189 doi: 10.1007/s11709-018-0486-2

摘要： Dynamic relaxation method (DRM) is one of the suitable numerical procedures for nonlinear structural analysis. Adding the fictitious inertia and damping forces to the static equation, and turning it to the dynamic system, are the basis of this technique. Proper selection of the DRM artificial factors leads to the better convergence rate and efficient solutions. This study aims to increase the numerical stability, and to decrease the analysis time. To fulfil this objective, the reduction rate of analysis error for consecutive iterations is minimized. Based on this formulation, a new time step is found for the viscous dynamic relaxation. After combining this novel relationship with the other DRM factors, various geometrical nonlinear structures, such as, trusses, frames and shells are analyzed. The obtained results verify the efficiency of authors’ scheme.

关键词： viscous dynamic relaxation time step displacement error geometric nonlinear analysis

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Numerical analysis of vehicle-bridge coupling vibration concerning nonlinear stress-dependent damping

Pengfei LI; Jinquan ZHANG; Shengqi MEI; Zhenhua DONG; Yan MAO

《结构与土木工程前沿（英文）》 2022年第16卷第2期页码 239-249 doi: 10.1007/s11709-021-0804-y

摘要： Damping is known to have a considerable influence on the dynamic behavior of bridges. The fixed damping ratios recommended in design codes do not necessarily represent the complicated damping characteristics of bridge structures. This study investigated the application of stress-dependent damping associated with vehicle-bridge coupling vibration and based on that investigation proposed the stress-dependent damping ratio. The results of the investigation show that the stress-dependent damping ratio is significantly different from the constant damping ratio (5%) defined in the standard specification. When vehicles travel at speeds of 30, 60, and 90, the damping ratios of the bridge model are 3.656%, 3.658%, and 3.671%, respectively. The peak accelerations using the regular damping ratio are 18.9%, 21.3%, and 14.5% of the stress-dependent damping ratio, respectively. When the vehicle load on the bridge is doubled, the peak acceleration of the mid-span node increases by 5.4 times, and the stress-related damping ratio increases by 2.1%. A corrugated steel-web bridge is being used as a case study, and the vibration response of the bridge is compared with the measured results. The acceleration response of the bridge which was calculated using the stress-dependent damping ratio is significantly closer to the measured acceleration response than that using the regular damping ratio.

关键词： vehicle-bridge vibration system dynamic analysis stress-dependent damping energy dissipation

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Evaluation of site response characteristic using nonlinear method (Case study: Babol, Iran)

Asskar Janalizadeh CHOOBBASTI, Sadegh REZAEI, Farzad FARROKHZAD, Pedram Haidarzaeh AZAR

《结构与土木工程前沿（英文）》 2014年第8卷第1期页码 69-82 doi: 10.1007/s11709-014-0231-4

摘要： In this the present study, an attempt has been made to evaluate the seismic hazard considering local site effects by carrying out detailed geotechnical site characterization in Babol, Iran. Use of geotechnical data and synthesis of drilling data extracted from the Babol’s subsurface database have enabled authors to determine the geotechnical properties of each site. These data are consisted of twenty five boreholes up to depth of 40 m. Based on the obtained data from geotechnical investigation the study area is divided to five zones. Dynamic analysis was performed in time domain, using fully nonlinear model by PLAXIS. A series of analysis in the study area showed the site period, ranging from 0.4 to 0.8 s. Finally the obtained response spectra from fully nonlinear method were compared with site response spectra of Iran’s 2800 (earthquake) code.

关键词： fully nonlinear method site effect dynamic analysis response spectra

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Finding buckling points for nonlinear structures by dynamic relaxation scheme

Mohammad REZAIEE-PAJAND, Hossein ESTIRI

《结构与土木工程前沿（英文）》 2020年第14卷第1期页码 23-61 doi: 10.1007/s11709-019-0549-z

摘要： Dynamic Relaxation Method (DRM) is an explicit approach for solving the simultaneous systems of equations. In this tactic, the fictitious mass and damping are added to the static governing equations, and an artificial dynamic system is constructed. By using DRM for nonlinear analysis, the structural static equilibrium path is obtained. This outcome is extremely valuable, since it leads to the behavior of structures. Among the finding related to the structural static path are the critical and buckling points for nonlinear structures. In this paper, a new way for calculating the load factor is proposed by setting the external work zero. Mixing the dynamic relaxation scheme with external work technique has not been formulated so far. In all incremental-iterative methods, the load factor increment sign should be determinated by extra calculations. This sign leads to increase or decrease of the load increment. It is worth emphasizing that sign of the load factor increment changes at the load limit points. Therefore, the sign determinations are required in the common work control methods. These disadvantages are eliminated in the proposed algorithm. In fact, the suggested load factor depends only on the Dynamic Relaxation (DR) fictitious parameters. Besides, all DR calculations are performed via vector operation. Moreover, the load factor is calculated only by one formula, and it has the same relation in the all solution processes. In contrast to the arc length techniques, which requires the sign determined, the proposed scheme does not need any sign finding. It is shown that author’s technique is quicker than the other dynamic relaxation strategies. To prove the capability and efficiency of the presented scheme, several numerical tests are performed. The results indicate that the suggested approach can trace the complex structural static paths, even in the snap-back and snap-through parts.

关键词： load factor external work dynamic relaxation static equilibrium path large displacement

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Nonlinear dynamic behavior of rotating blade with breathing crack

Laihao YANG, Zhu MAO, Shuming WU, Xuefeng CHEN, Ruqiang YAN

《机械工程前沿（英文）》 2021年第16卷第1期页码 196-220 doi: 10.1007/s11465-020-0609-z

摘要： This study aims at investigating the nonlinear dynamic behavior of rotating blade with transverse crack. A novel nonlinear rotating cracked blade model (NRCBM), which contains the spinning softening, centrifugal stiffening, Coriolis force, and crack closing effects, is developed based on continuous beam theory and strain energy release rate method. The rotating blade is considered as a cantilever beam fixed on the rigid hub with high rotating speed, and the crack is deemed to be open and close continuously in a trigonometric function way with the blade vibration. It is verified by the comparison with a finite element-based contact crack model and bilinear model that the proposed NRCBM can well capture the dynamic characteristics of the rotating blade with breathing crack. The dynamic behavior of rotating cracked blade is then investigated with NRCBM, and the nonlinear damage indicator (NDI) is introduced to characterize the nonlinearity caused by blade crack. The results show that NDI is a distinguishable indicator for the severity level estimation of the crack in rotating blade. It is found that severe crack (i.e., a closer crack position to blade root as well as larger crack depth) is expected to heavily reduce the stiffness of rotating blade and apparently result in a lower resonant frequency. Meanwhile, the super-harmonic resonances are verified to be distinguishable indicators for diagnosing the crack existence, and the third-order super-harmonic resonances can serve as an indicator for the presence of severe crack since it only distinctly appears when the crack is severe.

关键词： rotating blade breathing crack nonlinear vibration nonlinear damage indicator

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PRESS-based EFOR algorithm for the dynamic parametrical modeling of nonlinear MDOF systems

Haopeng LIU, Yunpeng ZHU, Zhong LUO, Qingkai HAN

《机械工程前沿（英文）》 2018年第13卷第3期页码 390-400 doi: 10.1007/s11465-017-0459-5

摘要：

In response to the identification problem concerning multi-degree of freedom (MDOF) nonlinear systems, this study presents the extended forward orthogonal regression (EFOR) based on predicted residual sums of squares (PRESS) to construct a nonlinear dynamic parametrical model. The proposed parametrical model is based on the non-linear autoregressive with exogenous inputs (NARX) model and aims to explicitly reveal the physical design parameters of the system. The PRESS-based EFOR algorithm is proposed to identify such a model for MDOF systems. By using the algorithm, we built a common-structured model based on the fundamental concept of evaluating its generalization capability through cross-validation. The resulting model aims to prevent over-fitting with poor generalization performance caused by the average error reduction ratio (AERR)-based EFOR algorithm. Then, a functional relationship is established between the coefficients of the terms and the design parameters of the unified model. Moreover, a 5-DOF nonlinear system is taken as a case to illustrate the modeling of the proposed algorithm. Finally, a dynamic parametrical model of a cantilever beam is constructed from experimental data. Results indicate that the dynamic parametrical model of nonlinear systems, which depends on the PRESS-based EFOR, can accurately predict the output response, thus providing a theoretical basis for the optimal design of modeling methods for MDOF nonlinear systems.

关键词： MDOF dynamic parametrical model NARX model PRESS-based EFOR cantilever beam

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黄幼麟：Dynamic Consumer Preferences for Electric Vehicles — A Longitudinal Analysis（2020年7月12日）

2022年06月10日

关键词：能源

Nonlinear dynamic behaviour of a cam mechanism with oscillating roller follower in presence of profile

Walha LASSAAD, Tounsi MOHAMED, Driss YASSINE, Chaari FAKHER, Fakhfakh TAHER, Haddar MOHAMED

《机械工程前沿（英文）》 2013年第8卷第2期页码 127-136 doi: 10.1007/s11465-013-0254-x

摘要：

In this paper we investigate the nonlinear dynamic behaviour of a cam mechanism with oscillating roller follower in presence of defects. The nonlinear developed lumped-mass model includes eight degrees of freedom with two nonlinear hertzian contacts. The first one is located between cam and first roller while the second is between second roller and the sliding rod. The nonlinear dynamic behaviour is described by second order differential equations which are resolved by using the implicit Newmark algorithm combined with the Newton-Raphson iterative scheme. The influence of the cam profile error on the dynamic behaviour is also investigated.

关键词： cam nonlinear behaviour oscillating roller follower profile error

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Dynamics analysis of a cracked dual-disk over-hung rotor-bearing system

CHEN Hong, LI He, WEN Bang-chun, ZHANG Xiao-wei

《机械工程前沿（英文）》 2006年第1卷第2期页码 204-208 doi: 10.1007/s11465-006-0002-6

摘要： A dynamic model of a dual-disk vertical over-hung rotor-bearing system is developed, taking into account nonlinear oil-film force. Its dynamic behaviors are investigated by numerical Runge-Kutta method. Its bifurcation and chaos characteristics are analyzed with crack fault and without crack fault. By analyzing the bifurcation plot, Poincare section plots and amplitude spectra, we found that the crack greatly influences the dynamic characteristics of the rotor-bearing system. Because of the strong effect of the nonlinear oil-film force and crack to the system, 1/2 times, 1/3 times frequency components appear in the response spectrum map. The results may bring up theoretical references for fault diagnosis of rotor-bearing systems.

关键词： nonlinear oil-film diagnosis bifurcation dynamic numerical Runge-Kutta