Papers by Keyword: Nonlinearity

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Authors: Yong Qiang Li, Li Ping Jing, Hai An Liang, Yan Zou, Wei Feng Sun
Abstract: A three dimensional numerical model for a typical earth dam and its valley site was established and the nonlinear seismic response of this model was performed. Experimental data of cyclic triaxial tests were adopted to determine the curves of modulus ratio and damping ratio that vary with dynamic strain amplitude. Free-field artificial boundary and viscous artificial boundary were employed and the input waves were the revised ground motions obtained from the station near the dam. Distributions of the PGA, displacement, residual deformation, shear strain increment and element failure state were presented. Results demonstrate that the 3D local valley site effect has a significant influence on the seismic response of earth dam.
Authors: Miguel Munoz, Michele Iuliano, Bruno Briseghella
Abstract: In some cases, due to particular conditions, the project of a bridge requires the construction of high piers. The study of these structural elements needs to go beyond a simple linear analysis, especially considering the second order effects, that contemplate the possibility of instability of the pier due to the slenderness it. In this paper a toolbox that considers the geometrical nonlinearity, the nonlinearity mechanical behaviour of the materials and the time dependent properties of the concrete is presented. The assessment of the pier starts with the possibility of cracking in the section (material non linearity) with consequent loses of stiffness. The second step takes into account the increment of bending moment caused by the P-d effect (geometrical non linearity) and strictly related to the slenderness of the member. The last step is the evaluation of the increment of deformation caused by permanent loads, mainly due to the loss of the concrete stiffness in time for creep effect of concrete. In this paper, a detailed explanation of the automatic procedure is provided and finally the application to a real case of a bridge pier under a critical stage construction condition is presented.
Authors: Peng Li, Li Zhi Gu
Abstract: By analyzing factors affecting the accuracy of boring process on the precision boring machine, the article aims at putting forward a method of improving the accuracy of boring process by means of installing polymer elastic shock absorbers on unilateral boring tools. In addition, the situation of non-linear radial forced vibration is formulated by a dynamic model of second-order differential equation. Based on the model, vibration prevention principles of unilateral boring tools have been discussed and systematic parameters have been optimized for enhancement of the boring process accuracy.
Authors: Huai Ning Ruan, Di Wang, J. W. Ju
Abstract: In designing earth structures, various kinds of complex soils and rocks are constantly encountered. These geomaterials exhibit heterogeneous, nonlinear, and anisotropic behavior. A failure criterion for such complicated materials is proposed. This model is highly comprehensive. It characterizes heterogeneity, nonlinearity, and anisotropy simultaneously in one equation. Many classical failure criteria employed in geomechanics and plasticity are its special cases. The material parameters in the proposed criterion may be determined from tests of unconfined compression, uniaxial tension, biaxial compression, and direct shear. The case study illustrates the potential of the proposed model in engineering application.
Authors: Paola Antonaci, Pietro G. Bocca, Davide Masera, Nicola Maria Pugno, Marco Scalerandi, Fabrizio Sellone
Abstract: The results of an experimental research on plain concrete are presented. The non-linear behavior of both virgin and damaged samples is investigated by means of ultrasonic tests: recent theoretical models, indeed, have pointed out that mono-frequency ultrasonic excitations bring to light such phenomena as harmonic generation and sidebands production, which are essentially due to the material classical or hysteretic non-linearity. The estimation of the harmonic components parameters (amplitudes and phases) is achieved through a signal processing technique based on MUltiple SIgnal Classification (MUSIC) system, which reveals to be optimal for the specific signal model here considered. The experiments described in this paper show that the material non-linear features increase with increasing level of internal micro-cracking, thus suggesting the possibility to use the ultrasonic signal analysis in the frequency domain as a valuable tool for damage assessment.
Authors: Venkatesh Chenniappan, Reza Moheimani, Mehmet Yuce
Abstract: A novel MEMS resonator employing “capacitance-shaping” principle to generate sinusoidal signals is proposed. FEM simulations are done to study the structure. Preliminary characterizations on devices fabricated through SOI-MUMPS are carried-out to study the frequency tuning of the resonator by electrostatic actuation. Variants of the proposed structure are presented. Second order dynamical models of the devices are derived.
Authors: Juraj Králik
Abstract: This paper presents the methodology of the reliability analysis of the fire resistance of the steel structure of the cable way in NPP. The elastic and plastic solution of the steel structure under fire loads is discussed. The deterministic and probability analysis of the fire resistance of the steel structures are considered. The executed fire resistance analysis of the steel structures is investigated as the influence of temperature, permanent and variable loads. A Response Surface Method (RSM) for the nonlinear analysis of the fire structure reliability was used on program ANSYS. The advantages and disadvantages of the deterministic and probabilistic analysis of the fire safety are discussed.
Authors: Ji Young Lee, Jung Pyo Hong, Do Hyun Kang
Abstract: Inductance is an important parameter to assess electric motor characteristics. In this paper, the methods of apparent and incremental inductance calculations are introduced for a transverse flux linear motor (TFLM), which has a peculiar coil shape. To consider the nonlinearity of magnetic material, nonlinear analysis is performed by 3-dimensional equivalent magnetic circuit network (3D EMCN). The calculation method is verified by test results.
Authors: Chun Hua He, Qian Cheng Zhao, Da Chuan Liu, Zhen Chuan Yang, Gui Zhen Yan
Abstract: A detailed analysis about the nonlinearity of a mode-matching MEMS vibratory gyroscope is presented in this paper, then closed loop control for the sense mode is adopted to improved the performances. Experimental results figure out that the mode-matching gyroscope with closed loop controlled sense mode achieves a scale factor of 65mV/deg/s with nonlinearity of 0.05% and asymmetry of 0.1%, and a bias instability of 0.77deg/h, while they are 60mV/deg/s, 1%, 4.6% and 9.8deg/h in the open loop controlled sense mode system, respectively. These performances can be improved by more than one order of magnitude in the closed loop control system.
Authors: Zhi Xing Li, Li Hua Yang, Qing Chao Yang
Abstract: In this paper, the dynamic characteristics of Duffing strong nonlinear vibration absorber system with additional hard spring is analysed qualitatively. Based on synovial variable structure algorithm, the active control system model of the nonlinear dynamic vibration absorber is designed, and the effectiveness of the control model is verified by elevant examples. It’s found that with the additional hard spring Duffing strong nonlinear vibration absorber, the control effect of active absorption is superior to the passive absorber, so which has has important guiding significance to the design of actual engineering nonlinear vibration absorber.
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