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CONTENTS
Volume 22, Number 3, March 2016
 

Abstract
The flutter derivatives of bridge decks can be efficiently identified using the experimentally and/or numerically coupled forced vibration method. This paper addresses the issue of inherent requirement for adopting different frequencies of three modes in this method. The aerostatic force components and the inertia of force and moment are mathematically proved to exert no influence on identification results if the signal length (t) is integer (n=1,2,3...) times of the least common multiple (T) of three modal periods. It is one important contribution to flutter derivatives identification theory and engineering practice in this study. Therefore, it is unnecessary to worry about the determination accuracy of aerostatic force and inertia of force and moment. The influences of signal length, amplitude, and frequency ratio on flutter derivative are thoroughly investigated using a bridge example. If the signal length t is too short, the extraction results may be completely wrong, and particular attention should be paid to this issue. The signal length (N>5) is strongly recommended for improving parameter identification accuracy. The proposed viewpoints and conclusions are of great significance for better understanding the essences of flutter derivative identification through coupled forced vibration method.

Key Words
bridge; flutter derivative; forced vibration method; multiple-degree-of-freedom coupling; theoretical proof; exemplification

Address
Fuyou Xu, Xuyong Ying and Zhe Zhang: School of Civil Engineering, Dalian University of Technology, Dalian 116024, China

Abstract
In this paper, a refined shear deformation plate theory which eliminates the use of a shear correction factor was presented for FG sandwich plates composed of FG face sheets and an isotropic homogeneous core. The theory accounts for parabolic distribution of the transverse shear strains and satisfies the zero traction boundary conditions on the surfaces of the plate. 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 refined shear deformation plate theory, the governing equations of equilibrium are derived from the principle of virtual displacements. Numerical illustrations concern buckling behavior of FG sandwiches plates with Metal–Ceramic composition. Parametric studies are performed for varying ceramic volume fraction, volume fraction profiles, Boundary condition, and length to thickness ratios. The accuracy of the present solutions is verified by comparing the obtained results with the existing solutions.

Key Words
mechanical properties; functionally graded sandwich plate; buckling; shear deformation; volume fraction

Address
Z. Abdelhak:Department of Civil Engineering, Material and Hydrology Laboratory, University of Sidi Bel Abbes,
Faculty of Technology, Algérie;
Centre Universitaire Ahmed Zabana, 48000 Relizane, Algérie
L. Hadji, Z. Khelifa and T. Hassaine Daouadji:Department of Civil Engineering, Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Algérie;
Université Ibn Khaldoun, BP 78 Zaaroura, 14000 Tiaret, Algérie
E.A. Adda Bedia:Department of Civil Engineering, Material and Hydrology Laboratory, University of Sidi Bel Abbes,
Faculty of Technology, Algérie




Abstract
This paper describes an investigation of the net wind loads on solar panels and wind loads on the underlying roof surface for panels mounted parallel to pitched roofs of domestic buildings. Typical solar panel array configurations were studied in a wind tunnel and the aerodynamic shape factors on the panels were put in a form appropriate for the Australian/New Zealand Wind Actions Standard AS/NZS 1170.2:2011. The results can also be used to obtain more refined design data on individual panels within an array. They also suggest values for the aerodynamic shape factors on the roof surface under the panels, based on a gust wind speed at roof height, of 0.5 for wind blowing parallel to the ridge, and 0.6 for wind blowing perpendicular to the ridge. The net loads on solar arrays in the middle portion of the roof are larger than those on the same portion of the roof without any solar panels, thus resulting in increased loads on the underlying roof structure.

Key Words
wind load; solar panel; code; standard; low-rise building; roof

Address
C.J. Leitch and J.D. Ginger:Cyclone Testing Station, School of Engineering and Physical Sciences, James Cook University, Townsville, Queensland, Australia
J.D. Holmes:James Cook University, Townsville and JDH Consulting, Mentone, Victoria, Australia


Abstract
This work presents a simple hyperbolic shear deformation theory for analysis of functionally graded plates resting on elastic foundation. The proposed model contains fewer number of unknowns and equations of motion than the first-order shear deformation model, but the transverse shear stresses account for a hyperbolic variation and respect the tangential stress-free boundary conditions on the plate boundary surface without introducing shear correction factors. Equations of motion are obtained from Hamilton\'s principle. The Navier-type analytical solutions for simply-supported plates are compared with the existing solutions to demonstrate the accuracy of the proposed theory.

Key Words
shear deformation theory; vibration; functionally graded plate; elastic foundation

Address
Salima Abdelbari, Abdelkader Fekrar and Hayat Saidi: Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria
Abdelouahed Tounsi:Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology,
Civil Engineering Department, Algeria;
Laboratoire de Modélisation et Simulation Multi-échelle, Département de Physique, Faculté des Sciences Exactes, Département de Physique, Université de Sidi Bel Abbés, Algeria;
Algerian National Thematic Agency of Research in Science and Technology (ATRST), Algeria
E.A. Adda Bedia: Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology,
Civil Engineering Department, Algeria;
Algerian National Thematic Agency of Research in Science and Technology (ATRST), Algeria

Abstract
A preconditioning technique is presented for a simultaneous solution to wind-membrane interaction. In the simultaneous equations, a linear elastic model was employed to deal with the fluid-structure data transfer at the interface. A Lagrange multiplier was introduced to impose the specified boundary conditions at the interface and strongly coupled simultaneous equations are derived after space and time discretization. An initial linear elastic model preconditioner and modified one were derived by treating the linearized elastic model equation as a saddle point problem, respectively. Accordingly, initial and modified fluid-structure interaction (FSI) preconditioner for the simultaneous equations were derived based on the initial and modified linear elastic model preconditioners, respectively. Wind-membrane interaction analysis by the proposed preconditioners, for two and three dimensional membranous structures respectively, was performed. Comparison was made between the performance of initial and modified preconditioners by comparing parameters such as iteration numbers, relative residuals and convergence in FSI computation. The results show that the proposed preconditioning technique greatly improves calculation accuracy and efficiency. The priority of the modified FSI preconditioner is verified. The proposed preconditioning technique provides an efficient solution procedure and paves the way for practical application of simultaneous solution for wind-structure interaction computation.

Key Words
membrane structures; wind loading; fluid-structure interaction; simultaneous solution; preconditioning technique

Address
Fang-jin Sun:College of Civil Engineering and Architecture, Liaoning Technical University, Fuxin, Liaoning,123000, China;
State Key Laboratory of Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, China
Ming Gu: State Key Laboratory of Disaster Reduction in Civil Engineering, Tongji University,
Shanghai 200092, China



Abstract
Electricity is transmitted by transmission lines from the source of production to the distribution system and then to the end users. Failure of a transmission line can lead to devastating economic losses and to negative social consequences resulting from the interruption of electricity. A comprehensive in-house numerical model that combines the data of computational fluid dynamic simulations of tornado wind fields with three dimensional nonlinear structural analysis modelling of the transmission lines (conductors and ground-wire) is used in the current study. Many codes of practice recommend neglecting the tornado forces acting on the conductors and ground-wires because of the complexity in predicting the conductors\' response to such loads. As such, real transmission line systems are numerically simulated and then analyzed with and without the inclusion of the lines to assess the effect of tornado loads acting on conductors on the overall response of transmission towers. In addition, the behaviour of the conductors under the most critical tornado configuration is described. The sensitivity of the lines\' behaviour to the magnitude of tornado loading, the level of initial sag, the insulator\'slength, and lines self-weight is investigated. Based on the current study results, a recommendation is made to consider conductors and ground-wires in the analysis and design of transmission towers under the effect of tornado wind loads.

Key Words
transmission lines; conductors; ground-wire; tornado; F2; CFD simulation; wind loads

Address
Ahmed Hamada and Ashraf A. El Damatty: Department of Civil and Environmental Engineering, Faculty of Engineering, The University of Western Ontario, London, Ontario, Canada


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