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CONTENTS
Volume 19, Number 3, March 2017
 

Abstract
The present study deals with the propagation of Love wave (a type of surface wave) in crustal layer having temperature dependent inhomogeneity. It is assumed that the inhomogeneity in the crustal layer arises due to linear temperature variation in rigidity and density. The upper boundary of the crustal layer is traction free. Numerical results for Love wave are discussed by plotting analytical curves between phase velocity against wave number and stress against depth in the presence of inhomogeneity and temperature parameters. The effects boundary condition on the Love wave propagation in the crustal layer is also analyzed. The results presented in this study would be useful for seismologists and geologists.

Key Words
love waves; temperature; elasticity; inhomogeneity

Address
Rajneesh Kakar, Shikha Kakar: Chotti Baradari, 163/1, Jalandhar-144022, India

Rajeev Kumar Narang: Urban Estate, 1477/2, Dugri, Ludhiana, India

Abstract
In this paper, free vibration of functionally graded (FG) size-dependent nanobeams is studied within the framework of nonlocal Timoshenko beam model. It is assumed that material properties of the FG nanobeam, vary continuously through the thickness according to a power-law form. The small scale effect is taken into consideration based on nonlocal elasticity theory of Eringen. The non-classical governing differential equations of motion are derived through Hamilton

Key Words
free vibration; functionally graded nanobeam; timoshenko beam theory; differential transformation method; nonlocal elasticity theory

Address
Department of Mechanical Engineering, Faculty of Engineering, Imam Khomeini International University, Qazvin, Iran

Abstract
System identification of structures is one of the important aspects of structural health monitoring. The accuracy and efficiency of identification results is affected severely by measurement noises, especially when the structure system is large, such as bridge structures, and when online system identification is required. In this paper, the least square estimation (LSE) method is used combined with the substructure approach for identifying structural parameters of a cable-stay bridge with large degree of freedoms online. Numerical analysis is carried out by first dividing the bridge structure into smaller substructures and then estimates the parameters of each substructure online using LSE method. Simulation results demonstrate that the proposed approach is capable of identifying structural parameters, however, the accuracy and efficiency of identification results depend highly on the noise sensitivities of loading region, loading pattern as well as element size.

Key Words
structural health monitoring; LSE; system identification of structure; measurement noises

Address
Yaohua Yang, Hongwei Huang and Limin Sun: Department of Bridge Engineering, Tongji University, Shanghai, China

Hongwei Huang and Limin Sun: State Key Laboratory for Disaster Reduction in Civil Engineering, Tongji University, Shanghai, China

Abstract
Recently, there has been significant interest in structural health monitoring for civil engineering applications. In this research, a specially designed tendon, proposed by embedding FBG sensors into the center king cable of a 7-wire strand tendon, was applied for long-term health monitoring of tensile forces on a ground anchor. To make temperature independent sensors, the effective temperature compensation of FBG sensors must be considered. The temperature sensitivity coefficient

Key Words
effective temperature compensation; FBG sensors; long-term monitoring; ground anchor tensile force

Address
Department of Civil and Environmental Engineering, Chonnam National University, Yeosu 550-749, Korean

Abstract
Magnetorheological damper has received significant attention in recent years due to the reason that it can offer adaptability of active control devices without requiring the associated large power sources. In this paper, performance tests on a MR damper are carried out under different currents, excitation amplitudes and frequencies, the damping characteristics and energy dissipation capacity of the MR damper are analyzed. Elasto-plastic dynamic analysis on a space frame structure incorporated with MR dampers is conducted, and numerical analysis results show that MR dampers can significantly mitigate the structural vibration responses. Finally, the genetic algorithm with the improved binary crossover and mutation technique is adopted to optimize the arrangement of MR dampers. Numerical results show that dynamic responses of the optimal controlled structure are mitigated more effectively.

Key Words
magnetorheological damper; performance test; elasto-plastic analysis; genetic algorithm; optimization

Address
Fei-Hong Xu, Zhao-Dong Xu: Key Laboratory of C&PC Structures of the Ministry of Education, Southeast University, Nanjing, 210096, Jiangsu, P.R. China

Xiang-Cheng Zhang: School of Mechanics and Engineering Science, Zhengzhou University, Zhengzhou, 450001, Henan, P.R. China

Abstract
This work presents a simplified higher order shear deformation theory (HSDT) for thermal buckling analysis of cross-ply laminated composite plates. Unlike the existing HSDT, the present one has a new displacement field which introduces undetermined integral terms and contains only four unknowns. Governing equations are derived from the principle of the minimum total potential energy. The validity of the proposed theory is evaluated by comparing the obtained results with their counterparts reported in literature. It can be concluded that the proposed HSDT is accurate and simple in solving the thermal buckling behavior of laminated composite plates.

Key Words
thermal buckling; cross ply-laminated plates; HSDT; analytical modelling

Address
Abdelbaki Chikh, Abdelouahed Tounsi, Habib Hebali: University Ibn Khaldoun, BP 78 Zaaroura, 14000 Tiaret, Algerie

Abdelbaki Chikh, Abdelouahed Tounsi, Habib Hebali: Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria

Abdelouahed Tounsi: Laboratoire de Modelisation et Simulation Multi-echelle, Departement de Physique, Faculte des Sciences Exactes, Departement de Physique, Universite de Sidi Bel Abbes, Algeria

S. R. Mahmoud: Department of Mathematics, Faculty of Science, King Abdulaziz University, Saudi Arabia

S. R. Mahmoud: Mathematics Department, Faculty of Science, University of Sohag, Egypt

Abstract
The magneto-electro-elastic (MEE) material under thermal environment exhibits pyroelectric and pyromagnetic coefficients resulting in pyroelectric and pyromagnetic effects. The pyroelectric and pyromagnetic effects on the behavior of multiphase MEE sensors bonded on top surface of a mild steel beam under thermal environment is presented in this paper. The aim of the study is to find out how samples having different volume fractions of the multiphase MEE composite behave in sensor applications. This is studied at optimal location on the beam, where the maximum electric and magnetic potentials are induced due to pyroelectric and pyromagnetic effects under clamped-free and clamped-clamped boundary conditions. The sensor which is bonded on the top surface of the beam is modeled using 8-node brick element. The MEE sensor bonded on mild steel beam is subjected to uniform temperature rise of 50K. It is assumed that beam and sensor is perfectly bonded to each other. The maximum pyroelectric and pyromagnetic effects on electric and magnetic potentials are observed when volume fraction is vf=0.2. The boundary conditions significantly influence the pyroelectric and pyromagnetic effects on electric and magnetic potentials.

Key Words
magneto-electro-elastic sensor; pyroelectric; pyromagnetic; finite element; temperature

Address
P. Kondaiah: Department of Mechanical Engineering, School of Engineering Science, Mahindra École Centrale, Hyderabad, Telangana 500043, India

K. Shankar: Machine Design Section, Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai 600036, India


Abstract
In this paper, the buckling, and free vibration analysis of tapered functionally graded carbon nanotube reinforced composite (FG-CNTRC) micro Reddy beam under longitudinal magnetic field using finite element method (FEM) is investigated. It is noted that the material properties of matrix is considered as Poly methyl methacrylate (PMMA). Using Hamilton

Key Words
buckling, and free vibration analysis; FG-CNTRC micro-composite Reddy beam; various distribution patterns of CNTs; Strain gradient theory; longitudinal magnetic field; FEM

Address
Department of Solid Mechanics, Faculty of Mechanical Engineering, University of Kashan, P.O. Box: 87317-53153, Kashan, Iran

Abstract
Waste materials in concrete have been considered as one of the most important issues by the authorities, policy makers and researchers to maintain engineering serviceability in terms of economy, durability and sustainability. Therefore, evaluation and selection of waste materials with respect to multi criteria decision making (MCDM) for the construction industry has been gained importance for recovery and reuse. In this paper, Choquet integral based fuzzy approach is proposed for evaluating the most suitable waste materials with respect to compressive strength, tensile strength, flexural strength, compactness, toughness (resistivity for dynamic loads), water absorption and accessibility. On conclusion, waste tyre and silica fume were determined as the most suitable waste materials for concrete production. The obtained results are recommended to assist the authorities on configuring well designed strategies for construction industry with disposal materials.

Key Words
waste material; construction industry; fuzzy logic; multi criteria decision making; Choquet integral

Address
Onur Onat: Department of Civil Engineering, Munzur University, Aktuluk Campus 62000 Tunceli, Turkey

Erkan Celik: Department of Industrial Engineering, Munzur University, Aktuluk Campus 62000 Tunceli, Turkey

Abstract
Fiber Bragg grating (FBG) sensors are applied to structural health monitoring (SHM) in many areas due to their unique advantages such as ease of multiplexing and capability of absolute measurement. However, they are exposed to cyclic thermal load, generally in the temperature range of -20°C to 60°C, in railways during a long-term SHM and the cyclic thermal load can affect the mechanical strength of FBGs. In this paper, the effects of both cyclic thermal load and the reflectivity of FBGs on the mechanical strength are investigated though tension tests of FBG specimens after they are aged in a thermal chamber with temperature changes in a range from -20°C to 60°C for 300 cycles. Results from tension tests reveal that the mechanical strength of FBGs decreases about 8% as the thermal cycle increases to 100 cycles; the mechanical strength then remains steady until 300 cycles. Otherwise, the mechanical strength of FBGs with reflectivity of 6dB (70%) and 10dB (90%) exhibits degradation values of about 6% and 12%, respectively, compared to that with reflectivity of 3dB (50%) at 300 cycles. SEM photos of the Bragg grating parts also show defects that cause their strength degradation. Consequently, it should be considered that mechanical strength of FBGs can be degraded by both thermal cycles and the reflectivity if the FBGs are exposed to repetitive thermal load during a long-term SHM.

Key Words
structural health monitoring; fiber Bragg grating; thermal load; mechanical strength

Address
Heonyoung Kim, Donghoon Kang: Advanced Materials Research Team, Korea Railroad Research Institute, 176 Cheoldo bangmulgwan-ro,
Uiwang-si, Gyeonggi-do, 16105, Republic of Korea

Heonyoung Kim: School of Mechanical Engineering, Yonsei University, 50 Yonsei-ro, Seodaemum-gu, Seoul, 03722, Republic of Korea.

Dae-Hyun Kim: Department of Mechanical and Automotive Engineering, Seoul National University of Science and Technology,
232 Gongneung-ro, Nowon-gu, Seoul, 01811, Republic of Korea


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