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CONTENTS
Volume 21, Number 1, January 2018
 

Abstract
A method is proposed to detect structural damages in the presence of damping using noisy data. This method uses Frequency Response Function (FRF) and Mode-Shapes as the input parameters for a system of Couple Sparse Coding (CSC) to study the healthy state of the structure. To obtain appropriate patterns of FRF for CSC training, Principal Component Analysis (PCA) technique is adopted to reduce the full-size FRF to overcome over-fitting and convergence problems in machine-learning training. To verify the proposed method, a numerical two-story frame structure is employed. A system of individual CSCs is trained with FRFs and mode-shapes, and then termed ensemble to detect the health condition of the structure. The results demonstrate that the proposed method is accurate in damage identification even in presence of up to 20% noisy data and 5% unconsidered damping ratio. Furthermore, it can be concluded that CSC ensemble is highly efficient to detect the location and the severity of damages in comparison to the individual CSC trained only with FRF data.

Key Words
couple sparse coding; damage detection; frequency response function; principal component analysis; ensemble

Address
Milad Fallahian and Faramarz Khoshnoudian: Faculty of Civil Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran, Iran
Saeid Talaei: Young Researchers and Elite Club, Central Tehran Branch, Islamic Azad University, Tehran, Iran

Abstract
This work presents the buckling investigation of embedded orthotropic nanoplates such as graphene by employing a new refined plate theory and nonlocal small-scale effects. The elastic foundation is modeled as two-parameter Pasternak foundation. The proposed two-variable refined plate theory takes account of transverse shear influences and parabolic variation of the transverse shear strains within the thickness of the plate by introducing undetermined integral terms, hence it is unnecessary to use shear correction factors. Nonlocal governing equations for the single layered graphene sheet are obtained from the principle of virtual displacements. The proposed theory is compared with other plate theories. Analytical solutions for buckling loads are obtained for single-layered graphene sheets with isotropic and orthotropic properties. The results presented in this study may provide useful guidance for design of orthotropic graphene based nanodevices that make use of the buckling properties of orthotropic nanoplates.

Key Words
buckling; orthotropic nanoplates; nonlocal elasticity; Pasternak

Address
Miloud Yazid1, Houari Heireche: Laboratoire de Modélisation et Simulation Multi-échelle, Département de Physique, Faculté des Sciences Exactes, Département de Physique, Université de Sidi Bel Abbés, Algeria
Abdelouahed Tounsi: Laboratoire de Modélisation et Simulation Multi-échelle, Département de Physique, Faculté des Sciences Exactes, Département de Physique, Université de Sidi Bel Abbés, Algeria;
Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia;
3Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria
Abdelmoumen Anis Bousahla: Laboratoire de Modélisation et Simulation Multi-échelle, Département de Physique, Faculté des Sciences Exactes, Département de Physique, Université de Sidi Bel Abbés, Algeria;
Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria;
Centre Universitaire Ahmed Zabana de Relizane, Algeria
Mohammed Sid Ahmed Houari: Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria;
Université Mustapha Stambouli de Mascara, Department of Civil Engineering, Mascara, Algeria






Abstract
In the water-filling and preloading test, the sensing cables were installed on the surface of steel spiral case and in the surrounding concrete to monitor the strain distribution of several cross-sections by using Brillouin Optical Time Domain Analysis (BOTDA), a kind of distributed optical fiber sensing (DOFS) technology. The average hoop strain of the spiral case was about 330 u e and 590 u e when the water-filling pressure in the spiral case was 2.6 MPa and 4.1 MPa. The difference between the measured and the calculated strain was only about 50 u e. It was the first time that the stress adjustment of the spiral case was monitored by the sensing cable when the pressure was increased to 1 MPa and the residual strain of 20 u e was obtained after preloading. Meanwhile, the shrinkage of 70 ~ 100 u e of the surrounding concrete was effectively monitored during the depressurization. It is estimated that the width of the gap between the steel spiral case and the surrounding concrete was 0.51 ~ 0.75 mm. BOTDA based distributed optical fiber sensing technology can obtain continuous strain of the structure and it is more reliable than traditional point sensor. The strain distribution obtained by BOTDA provides strong support for the design and optimization of the spiral case structure.

Key Words
BOTDA; distributed optical fiber sensing; strain distribution; spiral case; water-filling; preloading; hydraulic structure

Address
Heliang Cui: School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China;
POWERCHINA Huadong Engineering Corporation Limited, Hangzhou 311222, China
Dan Zhang and Bin Shi: School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China
Shusheng Peng: Zhejiang Huadong Engineering Safety Technology Co.,Ltd., Hangzhou 311222, China


Abstract
Tuned Liquid Dampers (TLDs) have gained wide acceptance as a system for structural control and energy dissipation. However, they face limitation caused by low damping in deep water, which affects their efficiency. Another problem with deep water TLDs is that not all water depth participates in energy dissipation. This paper investigated the effect of upper mounted baffles on the effectiveness of TLDs. The Vertical Blockage Ratio (VBR) of baffles ranged from 10% - 90%. The TLD (with and without baffle), structure, and combined structure with TLD (with and without baffles) were subjected to free and harmonic forced vibrations. Results indicated that baffles could significantly enhance the energy dissipation of TLDs, thus reducing structural responses more than structures equipped with ordinary TLDs. It was found that, there was an optimum value of VBR in which the TLD\'s efficiency was maximized. When TLD had an appropriate VBR, the structural acceleration and displacement responses were suppressed significantly up to 51% and 56%, respectively.

Key Words
tuned liquid damper; baffle; vibration response; dynamic response; free vibration

Address
Hossein Shad: Department of civil Engineering, Hakim Sabzevari University, Sabzevar, Khorasan Razavi, Iran
Azlan bin Adnan, Hamid Pesaran Behbahani and Abdulkareem M. Oladimeji:Faculty of Civil Engineering, Universiti Teknologi Malaysia, Johor, Malaysia
Mohammadreza Vafaei: Centre for forensic Engineering, Faculty of Civil Engineering, Universiti Teknologi Malaysia, Johor, Malaysia

Abstract
Nondestructive testing methods are required to assess the condition of civil structures and formulate their maintenance programs. Axial force identification is required for several structural members of truss bridges, pipe racks, and space roof trusses. An accurate evaluation of in situ axial forces supports the safety assessment of the entire truss. A considerable redistribution of internal forces may indicate structural damage. In this paper, a novel compressive force identification method for prismatic members implemented using static deflections is applied to steel beams. The procedure uses the Euler–Bernoulli beam model and estimates the compressive load by using the measured displacement along the beam\'s length. Knowledge of flexural rigidity of the member under investigation is required. In this study, the deflected shape of a compressed steel beam is subjected to an additional vertical load that was short-term measured in several laboratory tests by using fiber Bragg grating–differential settlement measurement (FBG–DSM) sensors at specific cross sections along the beam\'s length. The accuracy of midspan deflections offered by the FBG–DSM sensors provided excellent force estimations. Compressive load detection accuracy can be improved if substantial second-order effects are induced in the tests. In conclusion, the proposed method can be successfully applied to steel beams with low slenderness under real conditions.

Key Words
deflected shape; FBG–DSM sensor; force identification; inverse problem; static test; steel beam

Address
Marco Bonopera: Bridge Engineering Division, National Center for Research on Earthquake Engineering, Taipei, Taiwan;
Department of Engineering, University of Ferrara, Ferrara, Italy
Kuo-Chun Chang: Department of Civil Engineering, National Taiwan University, Taipei, Taiwan
Chun-Chung Chen and Zheng-Kuan Lee: Bridge Engineering Division, National Center for Research on Earthquake Engineering, Taipei, Taiwan
Nerio Tullini: Department of Engineering, University of Ferrara, Ferrara, Italy



Abstract
In this article, an analytic non-classical model for the free vibrations of nanobeams accounting for surface stress effects is developed. The classical continuum mechanics fails to capture the surface energy effects and hence is not directly applicable at nanoscale. A general beam model based on Gurtin-Murdoch continuum surface elasticity theory is developed for the analysis of thin and thick beams. Thus, surface energy has a significant effect on the response of nanoscale structures, and is associated with their size-dependent behavior. To check the validity of the present analytic solution, the numerical results are compared with those obtained in the scientific literature. The influences of beam thickness, surface density, surface residual stress and surface elastic constants on the natural frequencies of nanobeams are also investigated. It is indicated that the effect of surface stress on the vibrational response of a nanobeam is dependent on its aspect ratio and thickness.

Key Words
surface stress effects; nanoscales; free vibration; Gurtin-Murdoch

Address
Djamel Ould Youcef and Abdelnour Benzair: Laboratoire de Modélisation et Simulation Multi-échelle, Département de Physique, Faculté des Sciences Exactes, Département de Physique, Université de Sidi Bel Abbés, Algeria
Abdelhakim Kaci: Université Dr Tahar Moulay, Faculté de Technologie, Département de Génie Civil et Hydraulique,
BP 138 Cité En-Nasr 20000 Saida, Algeria
Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria;
Abdelmoumen Anis Bousahla: Laboratoire de Modélisation et Simulation Multi-échelle, Département de Physique, Faculté des Sciences Exactes, Département de Physique, Université de Sidi Bel Abbés, Algeria;
Centre Universitaire Ahmed Zabana de Relizane, Algeria
Abdelouahed Tounsi: Laboratoire de Modélisation et Simulation Multi-échelle, Département de Physique, Faculté des Sciences Exactes, Département de Physique, Université de Sidi Bel Abbés, Algeria;
Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria;
Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals,31261 Dhahran, Eastern Province, Saudi Arabia






Abstract
In this paper, a novel higher-order shear deformation theory (HSDT) is proposed for the analysis of the hygro-thermo-mechanical behavior of functionally graded (FG) plates resting on elastic foundations. The developed model uses a novel kinematic by considering undetermined integral terms and only four variables are used in this model. The governing equations are deduced based on the principle of virtual work and the number of unknown functions involved is reduced to only four, which is less than the first shear deformation theory (FSDT) and others HSDTs. The Navier-type exact solutions for static analysis of simply supported FG plates subjected to hygro-thermo-mechanical loads are presented. The accuracy and efficiency of the present model is validated by comparing it with various available solutions in the literature. The influences of material properties, temperature, moisture, plate aspect ratio, side-to-thickness ratios and elastic coefficients parameters on deflections and stresses of FG plates are also investigated.

Key Words
bending; functionally graded materials; plate theory; hygro-thermo-mechanical loads

Address
Fouad Boukhelf: Laboratoire des Structures et Matériaux Avancés dans le Génie Civil et Travaux Publics (Département de Génie Civil &Travaux Publics, Faculté de Technologie, Université de Sidi Bel Abbes, Algeria
Mohamed Bachir Bouiadjra: Laboratoire des Structures et Matériaux Avancés dans le Génie Civil et Travaux Publics (Département de Génie Civil &Travaux Publics, Faculté de Technologie, Université de Sidi Bel Abbes, Algeria;
Algerian National Thematic Agency of Research in Science and Technology (ATRST), Algeria
Mohammed Bouremana: Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria
Abdelouahed Tounsi: 1Laboratoire des Structures et Matériaux Avancés dans le Génie Civil et Travaux Publics (Département de Génie Civil &Travaux Publics, Faculté de Technologie, Université de Sidi Bel Abbes, Algeria;
Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria;
Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals,
31261 Dhahran, Eastern Province, Saudi Arabia;
Algerian National Thematic Agency of Research in Science and Technology (ATRST), Algeria




Abstract
Wind induced large bending oscillation amplitudes in tall and slender telecommunication steel towers may lead to precocious fatigue cracks and consequent risk of collapse of these structures, many of them installed in rural areas alongside highways and in highly populated urban areas. Varying stress amplitudes at hot spots may be attenuated by means of passive control mechanical devices installed in the tower. This paper gives an account of both mathematical-numerical model and the technique applied to design and evaluate the performance of a double controller installed in existing towers which is composed by a nonlinear pendulum and a novel type of passive controller described herein as a planar motion disk mounted on shear springs. Results of experimental measurements carried out on two slender tubular steel towers under wind action demonstrate the efficiency of the double controllers in attenuating the towers bending oscillation amplitudes and consequent stress amplitudes extending the towers fatigue life.

Key Words
vibration control; steel towers; wind induced oscillations; field measurements; passive devices

Address
Ronaldo C. Battista and Michèle S. Pfeil: COPPE Institute, Federal University of Rio de Janeiro, C. Postal 68506, CEP 21941-972, Rio de Janeiro/RJ, Brazil
Eliane M.L. Carvalho: Department of Civil Engineering, Fluminense Federal University, Passos da Pátria 156-D, São Domingos, CEP 24210-240, Niterói/RJ, Brazil
Wendell D. Varela: Department of Structures, Federal University of Rio de Janeiro, Pedro Calmon 550-318, Cidade Universitária, CEP 21941-901, Rio de Janeiro/RJ, Brazil



Abstract
In this article, an exact analytical solution for mechanical buckling analysis of magnetoelectroelastic plate resting on pasternak foundation is investigated based on the third-order shear deformation plate theory. The in-plane electric and magnetic fields can be ignored for plates. According to Maxwell equation and magnetoelectric boundary condition, the variation of electric and magnetic potentials along the thickness direction of the plate is determined. The von Karman model is exploited to capture the effect of nonlinearity. Navier\'s approach has been used to solve the governing equations for all edges simply supported boundary conditions. Numerical results reveal the effects of (i) lateral load, (ii) electric load, (iii) magnetic load and (iv) higher order shear deformation theory on the critical buckling load have been investigated. These results must be the analysis of intelligent structures constructed from magnetoelectroelastic materials.

Key Words
buckling; piezoelectric; plates; shear deformation theories

Address
Mokhtar Ellali and Fouad Bourada: Smart structures Laboratory, University Centre of Ain Temouchent, Ain Temouchent 46000, Algeria;
Department of Civil Engineering, University Centre of Ain Temouchent, Algeria
Khaled Amara: Laboratory of Materials and Hydrology (LMH), University of Sidi Bel Abbes, Sidi Bel Abbes 22000, Algeria;
Department of Civil Engineering, University Centre of Ain Temouchent, Algeria
Mokhtar Bouazza: Laboratory of Materials and Hydrology (LMH), University of Sidi Bel Abbes, Sidi Bel Abbes 22000, Algeria;
Department of Civil Engineering, University of Bechar, Bechar 8000, Algeria



Abstract
Structural monitoring is the most important part of the construction and operation of the embankment dams. Appropriate instruments selection for dams is vital, as inappropriate selection causes irreparable loss in critical condition. Due to the lack of a systematic approach to determine adequate instruments, a framework based on three comparable Multi-Attribute Decision Making (MADM) methods, which are VIKOR, technique of order preference by similarity to ideal solution (TOPSIS) and Preference ranking organization method for enrichment evaluation (PROMETHEE), has been developed. MADM techniques have been widely used for optimizing priorities and determination of the most suitable alternatives. However, the results of the different methods of MADM have indicated inconsistency in ranking alternatives due to closeness of judgements from decision makers. In this study, 9 criteria and 42 geotechnical instruments have been applied. A new method has been developed to determine the decision makers\' importance weights and an aggregation method has been introduced to optimally select the most suitable instruments. Consequently, the outcomes of the aggregation ranking correlate about 94% with TOPSIS and VIKOR, and 83% with PROMETHEE methods\'results providing remarkably appropriate prioritisation of instruments for embankment dams.

Key Words
management; embankment dam; field instrumentation; geotechnical engineering; structural monitoring; decision making

Address
Isa Masoumi and Kaveh Ahangari: Department of Mining Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran
Ali Noorzad: Faculty of Civil, Water and Environmental Engineering, Shahid Beheshti University, Tehran, Iran


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