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China Ocean Engineering 2018年第3期32卷 266-277页

作者： Arash SHAHBAZTABAR ahmad rahbar-ranji Department of Ocean Engineering AmirK abir University of Technology

Free vibration analysis of symmetrically laminated composite plates resting on Pasternak elastic support and coupled with an ideal, incompressible and inviscid fluid is the objective of the present work. The fluid domain is considered to be infinite in the length direction but bounded in the depth and width directions. In order to derive the eigenvalue equation, Rayleigh-Ritz method is applied for the fluid-plate-foundation system. The efficiency of the method is proved by comparison studies with those reported in the open literature. At the end, parametric studies are carried out to examine the impact of different parameters on the natural frequencies.

关键词： free vibration analysis laminated composite plate fluid-plate-foundation interaction Rayleigh-Ritz method Pasternak foundation

Free vibration analysis of non-homogeneous orthotropic plates resting on Pasternak elastic foundation by Rayleigh-Ritz method

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Journal of Central South University 2016年第2期23卷 413-420页

作者： ahmad rahbar-ranji Arash Shahbaztabar Department of Ocean Engineering Amir Kabir University of Technology

Free vibration analysis of non-homogeneous orthotropic plates resting on a Pasternak type of elastic foundation is investigated. A set of admissible orthogonal polynomials are generated with Gram-Schmidt orthogonalization procedure and adopted in the Rayleigh-Ritz method. Accuracy and applicability of the method are examined by comparison of the results for different boundary conditions and material types with those available in literature. It is found that this method has good accuracy regardless of type of boundary condition and yields very accurate results even with low number of terms of orthogonal polynomials for the first mode of vibration. For higher modes of vibration, higher terms of orthogonal polynomials should be used. The effects of foundation parameter, density and non-homogeneity parameters on natural frequency are examined. It is concluded that natural frequency of plates are more sensitive to shearing layer coefficient rather than Winkler coefficient and density parameter has weakening effect on natural frequency.

关键词： free vibration non-homogeneous orthotropic plate Pastemak foundation Rayleigh-Ritz method Gram-Schmidt procedure

Modeling of fluid-induced vibrations and identification of hydrodynamic forces on flow control valves

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Journal of Central South University 2015年第7期22卷 2596-2603页

作者： Samad Mehrzad Ilgar Javanshir ahmad rahbar ranji Seyyed Hadi Taheri Department of Maritime Engineering Science and Research Branch Islamic Azad University Young Researchers and Elite Club Tabriz Branch Islamic Azad University Department of Maritime Engineering Amirkabir University

Dynamics and vibration of control valves under flow-induced vibration are analyzed. Hydrodynamic load characteristics and structural response under flow-induced vibration are mainly influenced by inertia, damping, elastic, geometric characteristics and hydraulic parameters. The purpose of this work is to investigate the dynamic behavior of control valves in the response to self-excited fluid flow. An analytical and numerical method is developed to simulate the dynamic and vibrational behavior of sliding dam valves, in response to flow excitation. In order to demonstrate the effectiveness of proposed model, the simulation results are validated with experimental ones. Finally, to achieve the optimal valve geometry, numerical results for various shapes of valves are compared. Rounded valve with the least amount of flow turbulence obtains lower fluctuations and vibration amplitude compared with the flat and steep valves. Simulation results demonstrate that with the optimal design requirements of valves, vibration amplitude can be reduced by an average to 30%.

关键词： flow-induced force hydrodynamic force finite element method(FEM) valve design fluid-structure interaction vibration

Buckling Analysis of Tapered Continuous Columns by Using Modified Buckling Mode Shapes

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Journal of Marine Science and Application 2019年第2期18卷 160-166页

作者： Sina Toosi Akbar Esfandiari ahmad rahbar ranji Department of Ocean Engineering AmirKabir University of Technology

Elastic critical buckling load of a column depends on various parameters,such as boundary conditions,material,and crosssection *** main purpose of this work is to present a new method for investigating the buckling load of tapered columns subjected to axial *** proposed method is based on modified buckling mode shape of tapered structure and perturbation *** mode shape of the damaged structure can be expressed as a linear combination of mode shapes of the intact *** in length in piecewise form can be positive or *** method can be used for single-span and continuous *** of results with those of finite element and Timoshenko methods shows the high accuracy and efficiency of the proposed method for detecting buckling load.

关键词： Buckling analysis Tapered column.Continuous columns Finite element method Modified buckling mode shapes