Abstract
On the basis of the geological conditions of high and steep mountainous slope on which an exit portal of an express railway tunnel with a bridge-tunnel combination is to be built, the composite structure of the exit portal with a bridge abutment of the bridge-tunnel combination is presented and the stability of the slope on which the express railway portal is to be built is analyzed using three dimensional (3D) numerical simulation in the paper. Comparison of the practicability for the reinforcement of slope with in-situ bored piles and diaphragm walls are performed so as to enhance the stability of the high and steep slope. The safety factor of the slope due to rockmass excavation both inside the exit portal and beneath the bridge abutment of the bridge-tunnel combination has been also derived using strength reduction technique. The
obtained results show that post tunnel portal is a preferred structure to fit high and steep slope, and the
surrounding rock around the exit portal of the tunnel on the high and steep mountainous slope remains stable
when rockmass is excavated both from the inside of the exit portal and underneath the bridge abutment after
the slope is reinforced with both bored piles and diaphragm walls. The stability of the high and steep slope is
principally dominated by the shear stress state of the rockmass at the toe of the slope; the procedure of
excavating rockmass in the foundation pit of the bridge abutment does not obviously affect the slope stability. In-situ bored piles are more effective in controlling the deformation of the abutment foundation pit in comparison with diaphragm walls and are used as a preferred retaining structure to uphold the stability of slope in respect of the lesser time, easier procedure and lower cost in the construction of the exit portal with bridge-tunnel combination on the high and steep mountainous slope. The results obtained from the numerical analysis in the paper can be used to guide the structural design and construction of express railway tunnel portal with bridge-tunnel combination on high and abrupt mountainous slope under similar situations.
Key Words
tunnel portal; high and abrupt slope; slope stability; safety factor; strength reduction method;
numerical simulation
Address
Xiaojun Zhou, Hongyun Hu: Key Laboratory of Transportation Tunnel Engineering of China Education Ministry,
School of Civil Engineering, Southwest Jiaotong University,Chengdu 610031, China
Bo Jiang, Yuefeng Zhou and Yong Zhu: The 1st Design Institute of Civil Engineering and Architecture,China Railway ErYuan Engineering Group
Co. Ltd. Chengdu 610031, China
Abstract
A conditional probability based approach known as Particle Filter Method (PFM) is a powerful tool for system parameter identification. In this paper, PFM has been applied to identify the vehicle parameters based on response statistics of the bridge. The flexibility of vehicle model has been considered in the formulation of bridge-vehicle interaction dynamics. The random unevenness of bridge has been idealized as non homogeneous random process in space. The simulated response has been contaminated with artificial
noise to reflect the field condition. The performance of the identification system has been examined for various measurement location, vehicle velocity, bridge surface roughness factor, noise level and assumption of prior probability density. Identified vehicle parameters are found reasonably accurate and reconstructed interactive force time history with identified parameters closely matches with the simulated results. The study also reveals that crude assumption of prior probability density function does not end up with an incorrect estimate of parameters except requiring longer time for the iterative process to converge.
Abstract
Fiber metal laminates (FMLs) represent a high-performance family of hybrid materials which consist of thin metal sheets bonded together with alternating unidirectional fiber layers .In this study, the buckling behavior of a FML circular cylindrical shell under axial compression is investigated via both analytical and finite element approaches. The governing equations are derived based on the first-order shear deformation theory and solved by the Navier solution method. Also, the buckling load of a FML cylindrical shell is calculated using linear eigenvalue analysis in commercial finite element software, ABAQUS. Due to lack of experimental and analytical data for buckling behavior of FML cylindrical shells in the literature, the proposed model is simplified to the full-composite and full-metal cylindrical shells and buckling loads are compared with the available results. Afterwards, the effects of FML parameters such as metal volume fraction (MVF), composite fiber orientation, stacking sequence of layers and geometric parameters are studied on the buckling loads. Results show that the FML layup has the significant effect on the buckling loads of FML cylindrical shells in comparison to the full-composite and full-metal shells. Results of this paper hopefully provide a useful guideline for engineers to design an efficient and economical structure.
Key Words
buckling; fiber metal laminate (FML); analytical modelling; finite element analysis
Address
Ali M. Moniri Bidgoli: Faculty of Mechanical Engineering, College of Engineering, University of Tehran, 515-14395, Tehran, Iran
Mohammad Heidari-Rarani: Department of Mechanical Engineering, Faculty of Engineering, University of Isfahan, 81746-73441, Isfahan, Iran
Abstract
This paper presents the development of methodologies using Extended Finite Element Method (XFEM) for cracked unstiffened and concentric stiffened panels subjected to constant amplitude tensile fatigue loading. XFEM formulations such as level set representation of crack, element stiffness matrix formulation and numerical integration are presented and implemented in MATLAB software. Stiffeners of the stiffened panels are modelled using truss elements such that nodes of the panel and nodes of the stiffener coincide. Stress Intensity Factor (SIF) is computed from the solutions of XFEM using domain form of interaction integral. Paris
Key Words
extended finite element method; fatigue; stress intensity factor; stiffened panels
Address
M.R. Nanda Kumar: Bhabha Atomic Research Centre, Mumbai, 400085, India
A. Ramachandra Murthy, Smitha Gopinath and Nagesh R. Iyer: CSIR-Structural Engineering Research Centre, Chennai, 600113, India
Abstract
This investigation is concerned with the disturbances in a homogeneous transversely isotropic thermoelastic rotating medium with two temperature, in the presence of the combined effects of Hall currents and magnetic field due to normal force of ramp type. The formulation is applied to the thermoelasticity theories developed by Green-Naghdi Theories of Type-II and Type-III. Laplace and Fourier transform technique is applied to solve the problem. The analytical expressions of displacements, stress components, temperature change and current density components are obtained in the transformed domain. Numerical inversion technique has been applied to obtain the results in the physical domain. Numerically simulated results are depicted graphically to show the effects of Hall current and anisotropy on the resulting quantities. Some special cases are also deduced from the present investigation.
Key Words
transversely isotropic; thermoelastic; laplace transform; fourier transform; normal force; hall
current
Address
Rajneesh Kumar: Department of Mathematics, Kurukshetra University, Kurukshetra, Haryana, India
Nidhi Sharma: Department of Mathematics, MM University, Mullana, Ambala, Haryana, India
Parveen Lata: Department of Basic and Applied Sciences, Punjabi University, Patiala, Punjab, India
Abstract
In the present study, modelling and vibration control of axially moving laminated Carbon nanotubes/fiber/polymer composite (CNTFPC) plate under initial tension are investigated. Orthotropic visco-Pasternak foundation is developed to consider the influences of orthotropy angle, damping coefficient, normal and shear modulus. The governing equations of the laminated CNTFPC plates are derived based on new form of first-order shear deformation plate theory (FSDT) which is simpler than the conventional one due to reducing the number of unknowns and governing equations, and significantly, it does not require a
shear correction factor. Halpin-Tsai model is utilized to evaluate the material properties of two-phase composite consist of uniformly distributed and randomly oriented CNTs through the epoxy resin matrix. Afterwards, the structural properties of CNT reinforced polymer matrix which is assumed as a new matrix and then reinforced with E-Glass fiber are calculated by fiber micromechanics approach. Employing Hamilton
Key Words
vibration/vibration control; plate/shell structures; laminates; composites; fiber reinforced
Address
Ali Ghorbanpour Arani, Elham Haghparast and Hassan Baba Akbar Zarei: Department of Mechanical Engineering, University of Kashan, Kashan, Iran
Abstract
In this paper, a new first shear deformation plate theory based on neutral surface position is developed for the static and the free vibration analysis of functionally graded plates (FGPs). Moreover, the number of unknowns of this theory is the least one comparing with the traditional first-order and the other higher order shear deformation theories. The neutral surface position for a functionally graded plate which its material properties vary in the thickness direction is determined. The mechanical properties of the plate are assumed to vary continuously in the thickness direction by a simple power-law distribution in terms of the volume fractions of the constituents. Based on the present shear deformation plate theory and the neutral surface concept, the governing equations are derived from the principle of Hamilton. There is no stretchingbending coupling effect in the neutral surface based formulation. Numerical illustrations concern flexural
and dynamic behavior of FG plates with Metal-Ceramic composition. Parametric studies are performed for
varying ceramic volume fraction, length to thickness ratios. The accuracy of the present solutions is verified
by comparing the obtained results with the existing solutions.
Key Words
functionally graded material; first shear deformation theory; neutral surface position; volume
fraction
Address
Lazreg Hadji, M. Ait Amar Meziane: Material and Hydrology Laboratory, Faculty of Technology, Civil Engineering Department, University of Sidi Bel Abbes, Algeria; Universite Ibn Khaldoun, BP 78 Zaaroura, 14000 Tiaret, Algerie
Z. Abdelhak: Material and Hydrology Laboratory, Faculty of Technology, Civil Engineering Department, University of Sidi Bel Abbes, Algeria; Centre Universitaire Ahmed Zabana, 48000 Relizane, Algerie
T. Hassaine Daouadji: Material and Hydrology Laboratory, Faculty of Technology, Civil Engineering Department, University of Sidi Bel Abbes, Algeria; Universite Ibn Khaldoun, BP 78 Zaaroura, 14000 Tiaret, Algerie
E.A Adda Bedia: Material and Hydrology Laboratory, Faculty of Technology, Civil Engineering Department, University of Sidi Bel Abbes, Algeria
Abstract
Bearing joint dynamic parameter identification is crucial in modeling the high speed spindles for machining centers used to predict the stability and natural frequencies of high speed spindles. In this paper, a hybrid method is proposed to identify the dynamic stiffness of bearing joint for the high speed spindles. The hybrid method refers to the analytical approach and experimental method. The support
stiffness of spindle shaft can be obtained by adopting receptance coupling substructure analysis method,
which consists of series connected bearing and joint stiffness. The bearing stiffness is calculated based on the
Hertz contact theory. According to the proposed series stiffness equation, the stiffness of bearing joint can be
separated from the composite stiffness. Then, one can obtain the bearing joint stiffness fitting formulas and
its variation law under different preload. An experimental set-up with variable preload spindle is developed
and the experiment is provided for the validation of presented bearing joint stiffness identification method.
The results show that the bearing joint significantly cuts down the support stiffness of the spindles, which
can seriously affects the dynamic characteristic of the high speed spindles.
Key Words
bearing joint; dynamic stiffness; hybrid method; high speed spindles
Address
Yongsheng Zhao, Bingbing Zhang, Guoping An, Zhifeng Liu and Ligang Cai: Key Laboratory of advanced manufacturing technology, Beijing University of Technology, Beijing, 100124, P.R. China
Abstract
This research is aimed to design and analyze the performance of double dynamic vibration absorber (DVA) using a pendulum and a spring-mass type absorber for reducing vibration of two-DOF vibration system. The conventional fixed-points method and genetics algorithm (GA) optimization procedure are utilized in designing the optimal parameter of DVA. The frequency and damping ratio are optimized to determine the optimal absorber parameters. The simulation results show that GA optimization
procedure is more effective in designing the double DVA in comparison to the fixed-points method. The experimental study is conducted to verify the numerical result.
Key Words
vibration; absorber; mass-spring; pendulum; GA
Address
Lovely Son, Mulyadi Bur, Meifal Rusli and Adriyan: Department of Mechanical Engineering, Faculty of Engineering, Andalas University, Kampus Limau Manis 25163, Indonesia
Abstract
In this paper the differential transformation method (DTM) is utilized for vibration and buckling analysis of nanotubes in thermal environment while considering the coupled surface and nonlocal effects. The Eringen
