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RISS 인기검색어
- 검색키워드
- 저자 : Mehrdad Mohammadnejad (검색결과 5 건)
- 무료
- 기관 내 무료
- 유료
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Mohammadnejad, Mehrdad,Kazemi, Hasan Haji Techno-Press 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.65 No.1
This paper presents a new and simple solution for determining the natural frequencies of framed tube combined with shear-walls and tube-in-tube systems. The novelty of the presented approach is based on the bending moment function approximation instead of the mode shape function approximation. This novelty makes the presented solution very simpler and very shorter in the mathematical calculations process. The shear stiffness, flexural stiffness and mass per unit length of the structure are variable along the height. The effect of the structure weight on its natural frequencies is considered using a variable axial force. The effects of shear lag phenomena has been investigated on the natural frequencies of the structure. The whole structure is modeled by an equivalent non-prismatic shear-flexural cantilever beam under variable axial forces. The governing differential equation of motion is converted into a system of linear algebraic equations and the natural frequencies are calculated by determining a non-trivial solution for the system of equations. The accuracy of the proposed method is verified through several numerical examples and the results are compared with the literature.
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Flapwise and non-local bending vibration of the rotating beams
Mehrdad Mohammadnejad,Hamed Saffari 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.72 No.2
Weak form integral equations are developed to investigate the flapwise bending vibration of the rotating beams. Rayleigh and Eringen nonlocal elasticity theories are used to investigate the rotatory inertia and Size-dependency effects on the flapwise bending vibration of the rotating cantilever beams, respectively. Through repetitive integrations, the governing partial differential equations are converted into weak form integral equations. The novelty of the presented approach is the approximation of the mode shape function by a power series which converts the equations into solvable one. Substitution of the power series into weak form integral equations results in a system of linear algebraic equations. The natural frequencies are determined by calculation of the non-trivial solution for resulting system of equations. Accuracy of the proposed method is verified through several numerical examples, in which the influence of the geometry properties, rotatory inertia, rotational speed, taper ratio and size-dependency are investigated on the natural frequencies of the rotating beam. Application of the weak form integral equations has made the solution simpler and shorter in the mathematical process. Presented relations can be used to obtain a close-form solution for quick calculation of the first five natural frequencies of the beams with flapwise vibration and non-local effects. The analysis results are compared with those obtained from other available published references.
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Optimization of lateral resisting system of framed tubes combined with outrigger and belt truss
Mohammadnejad, Mehrdad,Kazemi, Hasan Haji Techno-Press 2022 Advances in computational design Vol.7 No.1
In this paper, the optimum location of the belt truss-outrigger for a combined system of framed tube, shear core and outrigger-belt truss is calculated. The optimum location is determined by maximization of the first natural frequency. The framed tube is modeled using a non-prismatic cantilever beam with hollow box cross section. The governing differential equation is solved using the weak form integral equations and the natural frequencies of the structure are calculated. The graphs are introduced for quick calculation of the first natural frequency. The location of the belt truss-outrigger that maximizes the first natural frequency of the structure is introduced as an optimum location. The structure is modeled using SAP-2000 finite elements software. In the modelling, the location of the belt truss-outrigger is changed along the height of the structure. With various locations of the outrigger, the lateral deflection of the all stories and axial force in the columns of the outer tube are calculated. The analysis is repeated by locating the outrigger-belt truss at the optimum location. The analysis results are compared and effect of the optimum location on the lateral deflection and the shear lag phenomena are investigated.
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Mehrdad Mohammadnejad 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.55 No.3
In this paper, a new and simplified method is presented in which the natural frequencies of the uniform and non-uniform beams are calculated through simple mathematical relationships. The various vibration problems such as: Rayleigh beam under variable axial force, axial vibration of a bar with and without end discrete spring, torsional vibration of a bar with an attached mass moment of inertia, flexural vibration of the beam with laterally distributed elastic springs and also flexural vibration of the beam with effects of viscose damping are investigated. The governing differential equations are first obtained and then; according to a harmonic vibration, are converted into single variable equations in terms of location. Through repetitive integrations, the governing equations are converted into weak form integral equations. The mode shape functions of the vibration are approximated using a power series. Substitution of the power series into the integral equations results in a system of linear algebraic equations. The natural frequencies are determined by calculation of a non-trivial solution for system of equations. The efficiency and convergence rate of the current approach are investigated through comparison of the numerical results obtained with those obtained from other published references and results of available finite element software.
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Mehrdad Mohammadnejad,Hasan Haji-Kazemi 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.65 No.1
This paper presents a new and simple solution for determining the natural frequencies of framed tube combined with shear-walls and tube-in-tube systems. The novelty of the presented approach is based on the bending moment function approximation instead of the mode shape function approximation. This novelty makes the presented solution very simpler and very shorter in the mathematical calculations process. The shear stiffness, flexural stiffness and mass per unit length of the structure are variable along the height. The effect of the structure weight on its natural frequencies is considered using a variable axial force. The effects of shear lag phenomena has been investigated on the natural frequencies of the structure. The whole structure is modeled by an equivalent non-prismatic shear-flexural cantilever beam under variable axial forces. The governing differential equation of motion is converted into a system of linear algebraic equations and the natural frequencies are calculated by determining a non-trivial solution for the system of equations. The accuracy of the proposed method is verified through several numerical examples and the results are compared with the literature.
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