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CONTENTS
Volume 16, Number 3, September 2015
 

Abstract
Today, as railways increase their capacity and speeds, it is more important than ever to be completely aware of the state of vehicles fleet‟s condition to ensure the highest quality and safety standards, as well as being able to maintain the costs as low as possible. Operation of a modern, dynamic and efficient railway demands a real time, accurate and reliable evaluation of the infrastructure assets, including signal networks and diagnostic systems able to acquire functional parameters. In the conventional system, measurement data are reliably collected using coaxial wires for communication between sensors and the repository. As sensors grow in size, the cost of the monitoring system can grow. Recently, auto-powered wireless sensor has been considered as an alternative tool for economical and accurate realization of structural health monitoring system, being provided by the following essential features: on-board micro-processor, sensing capability, wireless communication, auto-powered battery, and low cost. In this work, an original harvester device is designed to supply wireless sensor system battery using train bogie energy. Piezoelectric materials have in here considered due to their established ability to directly convert applied strain energy into usable electric energy and their relatively simple modelling into an integrated system. The mechanical and electrical properties of the system are studied according to the project specifications. The numerical formulation is implemented with in-house code using commercial software tool and then experimentally validated through a proof of concept setup using an excitation signal by a real application scenario.

Key Words
wireless technology; energy harvesting; piezoelectric sensor

Address
Francesco Amoroso and Rosario Pecora, University of Napoli \"Federico II\", Industrial Engineering Department, Via Claudio, 21 -80125- Napoli, Italy
Monica Ciminello and Antonio Concilio, C.I.R.A.- Italian Aerospace Research Center, Smart Structures Lab, Via Maiorise 81043, Capua (CE), Italy

Abstract
A developed hybrid method for crack identification of beams is presented. Based on the Euler-Bernouli beam theory and concepts of fracture mechanics, governing equation of the cracked beams is reformulated. Finite element (FE) method as a powerful numerical tool is used to discritize the equation in space domain. After transferring the equations from time domain to frequency domain, frequencies and mode shapes of the beam are obtained. Efficiency of the governed equation for free vibration analysis of the beams is shown by comparing the results with those available in literature and via ANSYS software. The used equation yields to move the influence of cracks from the stiffness matrix to the mass matrix. For crack identification measured data are produced by applying random error to the calculated frequencies and mode shapes. An objective function is prepared as root mean square error between measured and calculated data. To minimize the function, hybrid genetic algorithms (GAs) and particle swarm optimization (PSO) technique is introduced. Efficiency, Robustness, applicability and usefulness of the mixed optimization numerical tool in conjunction with the finite element method for identification of cracks locations and depths are shown via solving different examples.

Key Words
a hybrid inverse method; crack identification; reformulated governing equation; optimization; hybrid GAs- PSO

Address
Ali. R. Vosoughi, Department of Civil and Environmental Engineering, School of Engineering Shiraz University, Shiraz, Iran

Abstract
Tendon failures in bonded post-tensioned bridges over the last two decades have motivated ongoing investigations on various aspects of unbonded tendons and their monitoring methods. Recent research shows that change of strain distribution in anchor heads can be useful in detecting wire breakage in unbonded construction. Based on this strain variation, this paper develops a damage detection model that enables an automated tendon monitoring system to identify and locate wire breaks. The first part of this paper presents an experimental program conducted to study the strain variation in anchor heads by generating wire breaks using a mechanical device. The program comprised three sets of tests with fully populated 19-strand anchor head and evaluated the levels of strain variation with number of wire breaks in different strands. The sensitivity of strain variation with wire breaks in circumferential and radial directions of anchor head in addition to the axial direction (parallel to the strand) were investigated and the measured axial strains were found to be the most sensitive. The second part of the paper focuses on formulating the wire breakage detection framework. A finite element model of the anchorage assembly was created to demonstrate the algorithm as well as to investigate the asymmetric strain distribution observed in experimental results. In addition, as almost inevitably encountered during tendon stressing, the effects of differential wedge seating on the proposed model have been analyzed. A sensitivity analysis has been performed at the end to assess the robustness of the model with random measurement errors.

Key Words
post-tensioned bridge; unbonded tendon; wire breakage; strain variation; post-tensioning anchorage; multi-strand tendon; damage detection algorithm; automated tendon monitoring

Address
A.B.M. Abdullah, Jennifer A. Rice and H.R. Hamilton, Department of Civil and Coastal Engineering, University of Florida, Gainesville, FL 32611, USA

Abstract
The most widely known form of multifunctional aircraft structure is smart structures for structural health monitoring (SHM). The aim is to provide automated systems whose purposes are to identify and to characterize possible damage within structures by using a network of actuators and sensors. Unfortunately, environmental and operational variability render many of the proposed damage detection methods difficult to successfully be applied. In this paper, an original robust damage detection approach using output-only vibration data is proposed. It is based on independent component analysis and matrix perturbation analysis, where an analytical threshold is proposed to get rid of statistical assumptions usually performed in damage detection approach. The effectiveness of the proposed SHM method is demonstrated numerically using finite element simulations and experimentally through a conformal load-bearing antenna structure and composite plates instrumented with piezoelectric ceramic materials.

Key Words
structural health monitoring; robust damage detection; decision-making; analytical threshold; matrix perturbation theory; range subspaces; independent component analysis; piezoelectric ceramic material; composite structures; conformal load-bearing antenna structure; impact damages

Address
Rafik Hajrya and NazihMechbal, Arts et Métiers ParisTech (ENSAM), Process and Engineering in Mechanics and Materials Laboratory (PIMM)
CNRS-UMR 8006-151 Boulevard de l\'hôpital, 75013, Paris, France

Abstract
The design of a passive control solution based on tuned mass dampers (TMD\'s) requires the estimation of the actual masses involved in the undesired vibration. This task may result not so straightforward as expected when the vibration resides in subsets of different structural components. This occurs, for instance, when the goal is to damp out vibrations on stays. The theoretical aspects are first discussed and a design process is formulated. For sake of exemplification, a multiple TMD\'s configurations is eventually conceived for an existing timber footbridge located in the municipality of Trasaghis (North-Eastern Italy). The bridge span is 83 m and the deck width is 3.82 m.

Key Words
footbridges; passive control; tuned mass damper; vibration mitigation; wind load

Address
Daniele Bortoluzzi, Lorenzo Elia and Lucia Faravelli, Department of Civil Engineering and Architecture, University of Pavia, Via Ferrata 3, 27100 Pavia (PV), Italy
Sara Casciati, Department of Civil Engineering and Architecture, University of Catania at Siracusa, P.za Federico di Svevia, 96100 Siracusa, Italy

Abstract
In this work, a novel artificial circular muscle based on shape memory alloy (S.M.A.) is proposed. The design is inspired from the natural circular muscles found in certain organs of the human body such as the small intestine. The heating of the prestrained SMA artificial muscle will induce its contraction. In order to measure the mechanical work provided in this case, the muscle will be mounted on a silicone rubber cylindrical tube prior to heating. After cooling, the reaction of the rubber tube will involve the return of the muscle to its prestrained state. A finite element model of the new SMA artificial muscle was built using the software \"ABAQUS\". The SMA thermomechanical behavior law was implemented using the user subroutine \"UMAT\". The numerical results of the finite element analysis of the SMA muscle are presented to shown that the proposed design is able to mimic the behavior of a natural circular muscle.

Key Words
shape memory alloy; bioinspiration; biomimetic; new design; artificial muscle; finite element analysis

Address
Moez Ben Jaber, Systems and Applied Mechanics Research Laboratory, Tunisia Polytechnic School, University of Carthage, B.P. 743, La Marsa 2078, Tunisia ;National Engineering School of Tunis, University of El-Manar, BP 37, Le Belvédère 1002 Tunis, Tunisia
Mohamed A. Trojette, College of Sciences and Techniques of Tunis, University of Tunis, BP 56, 5 Avenue Taha Hussein, Bâb
Manara, Tunis, Tunisia
Fehmi Najar, Systems and Applied Mechanics Research Laboratory, Tunisia Polytechnic School, University of Carthage, B.P. 743, La Marsa 2078, Tunisia

Abstract
This study discusses the use of Adaptive-Network-Based-Fuzzy-Inference-System (ANFIS) in predicting the shear strength of reinforced-concrete deep beams. 139 experimental data have been collected from renowned publications on simply supported high strength concrete deep beams. The results show that the ANFIS has strong potential as a feasible tool for predicting the shear strength of deep beams within the range of the considered input parameters. ANFIS‟s results are highly accurate, precise and therefore, more satisfactory. Based on the Sensitivity analysis, the shear span to depth ratio (a/d) and concrete cylinder strength (f) have major influence on the shear strength prediction of deep beams. The parametric study confirms the increase in shear strength of deep beams with an equal increase in the concrete strength and decrease in the shear span to-depth-ratio.

Key Words
deep beams; ultimate shear strength; ANFIS; LR

Address
Mohammad Mohammadhassani, Department of Structural Engineering, University of Malaya, Malaysia
Aidi MD. Saleh, Malaysian public work department, Ledang, Tangkak, 84900 Johor, Malaysia
M Suhatril and M. Safa, Department of Civil Engineering, University of Malaya, Malaysia

Abstract
Vibration-based monitoring is one approach used to perform structural condition assessment. By measuring structural response, such as displacement, dynamic characteristics of a structure may be estimated. Often, the primary dynamic responses in civil structures are below 5 Hz, making accurate low frequency measurement critical for successful dynamic characterization. In addition, static deflection measurements are useful for structural capacity and load rating assessments. This paper presents a DC coupled continuous wave radar to accurately detect both dynamic and static displacement. This low-cost radar sensor provides displacement measurements within a compact, wireless unit appropriate for a range of structural monitoring applications. The hardware components and operating mechanism of the radar are introduced and a series of laboratory experiments are presented to assess the performance characteristics of the radar. The laboratory and field experiments investigate the effect of factors such as target distance, motion amplitude, and motion frequency on the radar\'s measurement accuracy. The results demonstrate that the radar is capable of both static and dynamic displacement measurements with sub-millimeter accuracy, making it a promising technology for structural health monitoring.

Key Words
DC coupled radar; dynamic displacement; static deflection; moving load test

Address
Shanyue Guan and Jennifer A. Rice, Engineering School of Sustainable Infrastructure and Environment, University of Florida, Gainesville, FL, USA 32611
Changzhi Li, Yiran Li and Guochao Wang,Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, Texas, USA 79409

Abstract
Magneto-electro-elastic (MEE) materials under thermal environment exhibits pyroelectric and pyromagnetic coefficients resulting in pyroeffects such as pyroelectric and pyromagnetic. The pyroeffects on the behavior of multiphase MEE sensor bonded on top surface of a mild steel cylindrical shell under thermal environment is presented in this paper. The study aims to investigate how samples having different volume fractions of the multiphase MEE sensor behave due to pyroeffects using semi-analytical finite element method. This is studied at an optimal location on a mild steel cylindrical shell, where the maximum electric and magnetic potentials are induced due to these pyroeffects under different boundary conditions. It is assumed that sensor and shell is perfectively bonded to each other. The maximum pyroeffects on electric and magnetic potentials are observed when volume fraction is vf = 0.2. Additionally, the boundary conditions significantly influence the pyroeffects on electric and magnetic potentials.

Key Words
pyroelectric; pyromagnetic; magneto-electro-elastic sensor; cylindrical shell; semi-analytical finite element

Address
P. Kondaiah, Department of Mechanical Engineering, School of Engineering & Technology, Mahindra É cole Centrale, Hyderabad, Andhra Pradesh 500043, India
K. Shankar and N. Ganesan, Machine Design Section, Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai 600036, India

Abstract
In the work at hand, the development of a morphing flap, actuated through shape memory alloy load bearing elements, is described. Moving from aerodynamic specifications, prescribing the morphed shape enhancing the aerodynamic efficiency of the flap, a suitable actuation architecture was identified, able to affect the curvature. Each rib of the flap was split into three elastic elements, namely \"cells\", connected each others in serial way and providing the bending stiffness to the structure. The edges of each cell are linked to SMA elements, whose contraction induces rotation onto the cell itself with an increase of the local curvature of the flap airfoil. The cells are made of two metallic plates crossing each others to form a characteristic \"X\" configuration; a good flexibility and an acceptable stress concentration level was obtained non connecting the plates onto the crossing zone. After identifying the main design parameters of the structure (i.e. plates relative angle, thickness and depth, SMA length, cross section and connections to the cell) an optimization was performed, with the scope of enhancing the achievable rotation of the cell, its ability in absorbing the external aerodynamic loads and, at the same time, containing the stress level and the weight. The conceptual scheme of the architecture was then reinterpreted in view of a practical realization of the prototype. Implementation issues (SMA - cells connection and cells relative rotation to compensate the impressed inflection assuring the SMA pre-load) were considered. Through a detailed FE model the prototype morphing performance were investigated in presence of the most severe load conditions.

Key Words
shape memory alloys; smart structures; morphing; flap

Address
Salvatore Ameduri and Antonio Concilio, Smart Structures and Materials Lab., Centro Italiano Ricerche Aerospaziali, Via Maiorise, 81043, Capua (CE), Italy
Rosario Pecora, Department of Aerospace Engineering, Università degli Studi di Napoli \"Federico II\", Via Claudio, 21, 80125, Napoli, Italy


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