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CONTENTS
Volume 19, Number 3, September 2015
 

Abstract
A new refined hyperbolic shear and normal deformation beam theory is developed to study the free vibration and buckling of functionally graded (FG) sandwich beams under various boundary conditions. The effects of transverse shear strains as well as the transverse normal strain are taken into account. Material properties of the sandwich beam faces are assumed to be graded in the thickness direction according to a simple power-law distribution in terms of the volume fractions of the constituents. The core layer is still homogeneous and made of an isotropic material. Equations of motion are derived from Hamilton's principle. Analytical solutions for the bending, free vibration and buckling analyses are obtained for simply supported sandwich beams. Illustrative examples are given to show the effects of varying gradients, thickness stretching, boundary conditions, and thickness to length ratios on the bending, free vibration and buckling of functionally graded sandwich beams.

Key Words
functionally graded sandwich beam; refined shear deformation theory; stretching effect

Address
(1) Riadh Bennai, Hassen Ait Atmane :
Département de génie civil, Faculté de génie civil et d'architecture, Univesité Hassiba Benbouali de Chlef, Algeria;
(2) Hassen Ait Atmane, Abdelouahed Tounsi:
Material and Hydrology Laboratory, University of Sidi Bel Abbes,
Faculty of Technology, Civil Engineering Department, Algeria;
(3) Hassen Ait Atmane, Abdelouahed Tounsi:
Laboratoire des Structures et Matériaux Avancés dans le Génie Civil et Travaux Publics, Université de Sidi Bel Abbes, Faculté de Technologie, Département de génie civil, Algeria.

Abstract
The paper makes the experimental and finite-element-analysis investigation on the seismic behavior of the rebar-penetrated joint between gangue concrete filled steel tubular column and reinforced gangue concrete beam under low cyclic reversed loading. Two specimens are designed and conducted for the experiment to study the seismic behavior of the rebar-penetrated joint under cyclic loading. Then, finite element analysis models of the rebar-penetrated joint are developed using ABAQUS 6.10 to serve as the complement of the experiment and further analyze the seismic behavior of the rebar-penetrated joint. Finite element analysis models are also verified by the experimental results. Finally, the hysteretic performance, the bearing capacity, the strength degradation, the rigidity degradation, the ductility and the energy dissipation of the rebar-penetrated joint are evaluated in detail to investigate the seismic behavior of the rebar-penetrated joint through experimental results and finite element analysis results. The research demonstrates that the rebar-penetrated joint between gangue concrete filled steel tubular column and reinforced gangue concrete beam, with full and spindle-shaped load-displacement hysteretic curves, shows generally the high ductility and the outstanding energy-dissipation capacity. As a result, the rebar-penetrated joint exhibits the excellent seismic performance and meets the earthquake-resistant requirements of the codes in China. The research provides some references and suggestions for the application of the rebar-penetrated joint in the projects.

Key Words
gangue concrete filled steel tube; joint; reinforced gangue concrete beam; seismic behavior; energy dissipation; ductility

Address
(1) Guochang Li, Yuwei An, Xing Zhao:
School of Civil Engineering, Shenyang Jianzhu University, 9 Hunnan East Road, Shenyang, Liaoning 110168, P.R. China;
(2) Chen Fang:
Department of Civil Engineering, University of Texas at El Paso, 500 W. University Ave., El Paso, TX 79968, USA.

Abstract
Recent years, explosive welding structures have been widely used in many engineering fields. The bonding state detection of explosive welding structures is significant to prevent unscheduled failures and even catastrophic accidents. However, this task still faces challenges due to the complexity of the bonding interface. In this paper, a new method called dual-tree complex wavelet transform based permutation entropy (DTCWT-PE) is proposed to detect bonding state of such structures. Benefiting from the complex analytical wavelet function, the dual-tree complex wavelet transform (DTCWT) has better shift invariance and reduced spectral aliasing compared with the traditional wavelet transform. All those characters are good for characterizing the vibration response signals. Furthermore, as a statistical measure, permutation entropy (PE) quantifies the complexity of non-stationary signals through phase space reconstruction, and thus it can be used as a viable tool to detect the change of bonding state. In order to more accurate identification and detection of bonding state, PE values derived from DTCWT coefficients are proposed to extract the state information from the vibration response signal of explosive welding structure, and then the extracted PE values serve as input vectors of support vector machine (SVM) to identify the bonding state of the structure. The experiments on bonding state detection of explosive welding pipes are presented to illustrate the feasibility and effectiveness of the proposed method.

Key Words
explosive welding structure; bonding state detection; dual-tree complex wavelet transform; permutation entropy; vibration response signals analysis

Address
(1) Yue Si, ZhouSuo Zhang, Wei Cheng, FeiChen Yuan:
School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an 710049, China;
(2) Yue Si, Wei Cheng, FeiChen Yuan:
State Key Laboratory for Manufacturing Systems Engineering, Xi'an Jiaotong University, Xi'an 710049, China.

Abstract
This paper presents the experimental work on fatigue life and specific fatigue strength of circular hollow sectioned steel tube and wood filled circular hollow section steel tube. Burning effect was observed in the case of circular hollow sectioned steel tube when it is subjected to Maximum bending moment of 19613.30 N-mm at 4200 rpm, but this did not happen in the case of wood filled hollow section. Statistical analysis was done based on the experimental data and relations have been built to predict the number of cycles for the applied stress or vice versa. The relations built in this paper can safely be applied for design of the fatigue life or fatigue strength of circular hollow sections and wood filled hollow sections. Results were validated by static specific bending strengths determined by ANSYS using a known applied load.

Key Words
stiffness; fatigue life; specific fatigue strength; reversed cycle stress; S-N curve

Address
Department of PDM, Visvesvaraya Technological University, Belgaum, 590 014, India.


Abstract
The Metal Magnetic Memory (MMM) method is a non-destructive testing method based on an analysis of the self-magnetic leakage field distribution on the surface of a component. It is used for determining the stress concentration zones or any irregularities on the surface or inside the components fabricated from ferrous-based materials. Thus, this paper presents the MMM signal behaviour due to the application of fatigue loading. A series of MMM data measurements were performed to obtain the magnetic leakage signal characteristics at the elastic, pre-crack and crack propagation regions that might be caused by residual stresses when cyclic loadings were applied onto the A283 Grade C steel specimens. It was found that the MMM method was able to detect the defects that occurred in the specimens. In addition, a justification of the Self Magnetic Flux Leakage patterns is discussed for demonstrating the effectiveness of this method in assessing the A283 Grade C steel under cyclic loadings.

Key Words
fatigue; stress concentration; steel; metal magnetic memory; crack propagation

Address
Department of Mechanical & Materials Engineering, Faculty of Engineering and Built Enviroments, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia.


Abstract
Composite steel-concrete beams are used frequently in situations where axial forces are introduced. Some examples include the use in cable-stayed bridges or inclined members in stadia and bridge approach spans. In these situations, the beam may be subjected to any combination of flexure and axial load. However, modern steel and composite construction codes currently do not address the effects of these combined actions. This study presents an analysis of composite beams subjected to combined loadings. An analytical model is developed based on a cross-sectional analysis method using a strategy of successive iterations. Results derived from the model show an excellent agreement with existing experimental results. A parametric study is conducted to investigate the effect of axial load on the flexural strength of composite beams. The parametric study is then extended to a number of section sizes and employs various degrees of shear connection. Design models are proposed for estimating the flexural strength of an axially loaded member with full and partial shear connection.

Key Words
composite beams; combined actions; composite construction; axial force

Address
Centre for Infrastructure Engineering and Safety, School of Civil and Environmental Engineering, Faculty of Engineering, The University of New South Wales (UNSW) Sydney, NSW 2052, Australia.

Abstract
In this study, natural frequency analysis of a large deflected cantilever laminated composite beam fixed at both ends, which forms the case of a pre-stressed curved beam, is investigated. The laminated beam is considered to have symmetric and asymmetric lay-ups and the effective flexural modulus of the beam is used in the analysis. In order to obtain the pre-stressed composite curved beam case, an external vertical concentrated load is applied at the free end of a cantilever laminated composite beam and then the loading point of the deflected beam is fixed. The non-linear deflection curve of the flexible beam undergoing large deflection is obtained by the Reversion Method. The curved laminated composite beam is modeled by using the Finite Element Method with a straight-beam element approach. The effects of orientation angle and vertical load on the natural frequency parameter for the first four modes are examined and the results obtained are given in graphics. It has been found that the effect of the load parameter, which forms the curved laminated beam, on the natural frequency parameter, almost disappears after a certain value of the load parameter. This certain value differs for each laminated curved beam and each vibration mode.

Key Words
large deflection; laminated curved beam; vibration; non-linear deflection; finite element method

Address
Dokuz Eylul University, Department of Mechanical Engineering, 35397 Buca, Izmir, Turkey.

Abstract
Buckling Restrained Braces (BRB) have been widely used in the construction industry as they utilize the most desirable properties of both constituent materials, i.e., steel and concrete. They present excellent structural qualities such as high load bearing capacity, ductility, energy-absorption capability and good structural fire behaviour. The effects of size and type of filler material in the existed gap at the steel core-concrete interface as well as the element's cross sectional shape, on BRB's fire resistance capacity was investigated in this paper. A nonlinear sequentially-coupled thermal-stress three-dimensional model was presented and validated by experimental results. Variation of the samples was described by three groups containing, the steel cores with the same cross section areas and equal yield strength but different materials (metal and concrete) and sizes for the gap. Responses in terms of temperature distribution, critical temperature, heating elapsed time and contraction level of BRB element were examined. The study showed that the superior fire performance of BRB was obtained by altering the filler material in the gap from metal to concrete as well as by increasing the size of the gap. Also, cylindrical BRB performed better under fire conditions compared to the rectangular cross section.

Key Words
Buckling Restrained Braces (BRB); gap filler material; fire resistance; cross sectional shape; finite element analysis

Address
Construction Research Centre, Faculty of Civil Engineering, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Malaysia.

Abstract
A numerical solution using finite difference method to evaluate the thermal buckling of simply supported FGM plate with variable thickness is presented in this research. First, the governing differential equation of thermal stability under uniform temperature through the plate thickness is derived. Then, the governing equation has been solved using finite difference method. After validating the presented numerical method with the analytical solution, the finite difference formulation has been extended in order to include variable thickness. The accuracy of the finite difference method for variable thickness plate has been also compared with the literature where a good agreement has been found. Furthermore, a parametric study has been conducted to analyze the effect of material and geometric parameters on the thermal buckling resistance of the FGM plates. It was found that the thickness variation affects isotropic plates a bit more than FGM plates.

Key Words
FGM plate; thermal buckling; stability analysis; finite difference; numerical method

Address
(1) Otbi Bouguenina:
Department of Civil Engineering and Hydraulics, University of Saida, BP 138 Cité Ennacer, 20000 Saida, Algeria;
(2) Khalil Belakhdar:
Department of Science and Technology, University Centre of Tamanrasset, BP 10034 Sersouf, Tamanrasset, Algeria;
(3) Abdelouahed Tounsi, El Abbes Adda Bedia:
Laboratory of Materials and Hydrology, University of Sidi Bel Abbes, BP 89 Cité Ben M'hidi, 22000 Sidi Bel Abbes, Algeria.

Abstract
It is well known the importance of considering hysteretic energy demands for the seismic assessment and design of structures. In such a way that it is necessary to establish new parameters of the earthquake ground motion potential able to predict energy demands in structures. In this paper, several alternative vector-valued ground motion intensity measures (IMs) are used to estimate hysteretic energy demands in steel framed buildings under long duration narrow-band ground motions. The vectors are based on the spectral acceleration at first mode of the structure Sa(T1) as first component. As the second component, IMs related to peak, integral and spectral shape parameters are selected. The aim of the study is to provide new parameters or vector-valued ground motion intensities with the capacity of predicting energy demands in structures. It is concluded that spectral-shape-based vector-valued IMs have the best relation with hysteretic energy demands in steel frames subjected to narrow-band earthquake ground motions.

Key Words
intensity measures; hysteretic energy; steel frames; spectral shape; narrow-band motions

Address
(1) Edén Bojórquez, Laura Astorga, Alfredo Reyes-Salazar, Juan Velázquez, Luz Rivera:
Facultad de Ingenierĺa, Universidad Autónoma de Sinaloa, Calzada de las Américas y B. Universitarios s/n, 80040 Culiacán;
(2) Amador Terán-Gilmore:
Departamento de Materiales, Universidad Autónoma Metropolitana, México City, México;
(3) Juan Bojórquez:
Instituto de Ingenierĺa, Universidad Nacional Autónoma de México, México City, México.

Abstract
In this paper, viscous fluid induced nonlinear free vibration and instability analysis of a functionally graded carbon nanotube-reinforced composite (CNTRC) cylindrical shell integrated with two uniformly distributed piezoelectric layers on the top and bottom surfaces of the cylindrical shell are presented. Single-walled carbon nanotubes (SWCNTs) are selected as reinforcement and effective material properties of FG-CNTRC cylindrical shell are assumed to be graded through the thickness direction and are estimated through the rule of mixture. The elastic foundation is modeled by temperature-dependent orthotropic Pasternak medium. Considering coupling of mechanical and electrical fields, Mindlin shell theory and Hamilton\'s principle, the motion equations are derived. Nonlinear frequency and critical fluid velocity of sandwich structure are calculated based on differential quadrature method (DQM). The effects of different parameters such as distribution type of SWCNTs, volume fractions of SWCNTs, elastic medium and temperature gradient are discussed on the vibration and instability behavior of the sandwich structure. Results indicate that considering elastic foundation increases frequency and critical fluid velocity of system.

Key Words
nonlinear vibration; viscous fluid; FG-CNTRC; piezoelectric layers; DQM

Address
(1) Mahmood Rabani Bidgoli, Mohammad Saeed Karimi:
Faculty of Civil Engineering, Semnan University, Semnan, Iran;
(2) Mahmood Rabani Bidgoli, Mohammad Saeed Karimi:
Faculty of Mechanical Engineering, University of Kashan, Kashan, Iran;
(3) Ali Ghorbanpour Arani:
Institute of Nanoscience & Nanotechnology,University of Kashan, Kashan, Iran.

Abstract
Composite bonding steel plate (CBSP) is a newly developed type of structure strengthened technique applicable to the existing RC beam. This composite structure is applicable to strengthening the existing beam bearing high load. The strengthened beam consists of two layers of epoxy bonding prestressed steel plates and the RC beam sandwiched in between. The bonding enclosed and prestressed U-shaped steel jackets are applied at the beam sides. This technique is adopted in case of structures with high longitudinal reinforcing bar ratio and impracticable unloading. The prestress can be generated on the strengthening steel plates and jackets by using the CBSP technique before loading. The test results of full-scale CBSP strengthened beams show that the strength and stiffness are enhanced without reduction of their ductility. It is demonstrated that the strain hysteresis effect can be effectively overcome after prestressing on the steel plates by using such technique. The applied plates and jackets can jointly behave together with the existing beam under the action of epoxy bonding and the mechanical anchorage of the steel jackets. The simplified formulas are proposed to calculate the prestress and the ultimate capacities of strengthened beams. The accuracy of formulas was verified with the experimental results.

Key Words
composite bonding steel plate; reinforced concrete beam; prestressed steel plates; u-shaped steel jackets; epoxy bonding; ultimate capacity

Address
(1) Su-hang Yang, Shuang-yin Cao:
School of Civil Engineering, Southeast University, Nanjing, Jiangsu, 210096, China;
(2) Rui-nan Gu:
Jiangsu Research Institute of Building Science CO., LTD., Nanjing, 210008, China.

Abstract
The First Order Shear Deformation Theory (FOSDT) is considered to study the dynamic behavior of a bimorph beam. A delamination zone between the upper and the lower layer has been taken into consideration; the beam is discretised using the finite elements method (FEM). Several parameters are taken into consideration like structural damping, the geometry, the load nature and the configurations of the boundary conditions. Results show that the delamination between the upper and the lower layer affects considerably the actuation.

Key Words
piezoelectricity; bimorph beam; delamination; shear deformation

Address
(1) Adel Zemirline, Mohammed Ouali:
Laboratory of Research: "Structures" In the University of Saad Dahleb, Blida 09000, Algeria;
(2) Adel Zemirline:
The LMP2M laboratory, In the University of Yahia Fares, Ain D'heb Medea 26000, Algeria;
(3) Ali Mahieddine:
Energy and smart systems Laboratory, Khemis Miliana University, Algeria.

Abstract
Production and properties of metal matrix composites reinforced with an in-situ high aspect ratio AlB2 flake have been investigated. Boron 2.2wt.% was dissolved in pure Al and Al-Cu alloy at 1300°C by adding directly boron oxide which resulted in 4 vol.% reinforcing phase. The in-situ AlB2 flake concentration was increased up to 30 vol.% in order to increase the tensile strength of the composites. Hardness, compressive strength and tensile strength of the composite were measured and compared with their matrix. Results showed that 30 vol.% A1B2/Al composite show a 193% increase in the compressive strength and a 322% increase in compressive yield strength. Results also showed that ductility of composites decreases with adding AlB2 reinforcements.

Key Words
AlB2 composite; boron oxide; aluminum boride; in-situ composite

Address
(1) Ramazan Kayikci:
Sakarya University, Faculty of Technology, 54187, Sakarya, Turkey;
(2) Ömer Savaş:
Yıldız Technical University, Naval Architect and Marine Engineering Faculty, 34349, Istanbul, Turkey.


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