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CONTENTS
Volume 21, Number 2, February 2018
 

Abstract
Understanding the current status of a construction project is necessary to achieve successful on-site management. Real-time information delivery is a major concern for construction industry practitioners in order to expedite decisions and discussions. We propose the use of a first personal view (FPV) system of a quadcopter drone as a tool for monitoring on-site status and communicating between construction participants. The most important function of the drone FPV system is its ability to visually monitor construction site situations in real time. An on-site management system process is developed, verified, and applied to several construction work tasks after determining factors that affect efficient construction management. The proposed system is expected to assist the construction manager in achieving high efficiency.

Key Words
unmanned aerial vehicle (UAV); first personal view (FPV); on-site management; reinforced concrete work; construction management

Address
Seungho Kim and Sangyong Kim: School of Architecture, 280 Daehak-ro, Gyeongsan-si, Gyeongsangbuk-do, 38541, Republic of Korea

Abstract
A new type of cascade sandwiched piezoelectric ultrasonic transducer is presented and studied. The cascade transducer is composed of two traditional longitudinally sandwiched piezoelectric transducers, which are connected together in series mechanically and in parallel electrically. Based on the analytical method, the electromechanical equivalent circuit of the cascade transducer is derived and the resonance/anti-resonance frequency equations are obtained. The impedance characteristics and the vibrational modes of the transducer are analyzed. By means of numerical method, the dependency of the resonance/anti-resonance frequency and the effective electromechanical coupling coefficient on the geometrical dimensions of the cascade transducer are studied and some interesting conclusions are obtained. Two prototypes of the cascade transducers are designed and made; the resonance/anti-resonance frequency is measured. It is shown that the analytical resonance/anti-resonance frequencies are in good agreement with the experimental results. It is expected that this kind of cascade transducer can be used in large power and high intensity ultrasonic applications, such as ultrasonic liquid processing, ultrasonic metal machining and ultrasonic welding and soldering.

Key Words
cascade piezoelectric transducer; longitudinal vibration; sandwiched transducer; effective electromechanical coupling coefficient

Address
Shuyu Lin and Jie Xu: Shaanxi key Laboratory of Ultrasonics, Shaanxi Normal University, 620 West Chang

Abstract
The dynamic response of a finite length thermo-piezoelectric rod with variable material properties is investigated in the context of the fractional order theory of thermoelasticity. The rod is subjected to a moving heat source and fixed at both ends. The governing equations are formulated and then solved by means of Laplace transform together with its numerical inversion. The results of the non-dimensional temperature, displacement and stress in the rod are obtained and illustrated graphically. Meanwhile, the effects of the fractional order parameter, the velocity of heat source and the variable material properties on the variations of the considered variables are presented, and the results show that they significantly influence the variations of the considered variables.

Key Words
fractional order theory of thermoelasticity; thermo-piezoelectric coupling; Laplace transform; moving heat source; variable properties

Address
Yongbin Ma, Liuchan Cao and Tianhu He: School of Science, Lanzhou University of Technology, Lanzhou 730050, Peoples Republic of China

Abstract
Maintenance of deteriorated bridge structures has always been one of the challenging issues in developing countries as it is directly related to daily life of people including trade and economy. An effective maintenance strategy is highly dependent on timely inspections on the bridge health condition. This study is intended to investigate an approach for detecting bridge damage for the long-term health monitoring by use of copula theory. Long-term measured data for the seven-span plate-Gerber bridge is investigated. Autoregressive time series models constructed for the observed accelerations taken from the bridge are utilized for the computation of damage indicator for the bridge. The copula model is used to analyze the statistical changes associated with the modal parameters. The changes in the modal parameters with the time are identified by the copula statistical properties. Applicability of the proposed method is also discussed based on a comparison study among other approaches.

Key Words
copula; structural health monitoring; bridge structure; long-term assessment

Address
Yi Zhang and Chul-Woo Kim: Department of Civil and Earth Resources Engineering, Graduate School of Engineering, Kyoto University, Japan
Kong Fah Tee: Department of Engineering Science, University of Greenwich, United Kingdom
Akhil Garg and Ankit Garg: Department of Mechatronics Engineering, Shantou University, Shantou, China

Abstract
This paper focuses on the H filter design problem for offshore steel jacket platforms. Its objective is to design a full-order state observer for offshore platforms in presence of unknown disturbances. To make the method more practical, it is assumed that the measured variables are available at discrete-time instants with time-varying sampling time intervals. By modelling the sampling intervals as a bounded time-varying delay, the estimation error system is expressed as a time-delay system. As a result, the addressed problem can be transformed to the problem of stability of dynamic error between the system and the state estimator. Then, based on the Lyapunov-Krasovskii Functional (LKF), a stability criterion is obtained in the form of Linear Matrix Inequalities (LMIs). According to the stability criterion, a sufficient condition on designing the state estimator gain is obtained. In the end, the proposed method is applied to an offshore platform to show its effectiveness.

Key Words
offshore platforms; H filter; sampled-data; Lyapunov–Krasovskii functional method; time-delay

Address
Ali Kazemy: Department of Electrical Engineering, Tafresh University, P. O. Box 39518-79611, Tafresh, Iran

Abstract
Research on Lamb wave-based damage identification in plate-like structures depends on precise knowledge of dispersive wave velocity. However, boundary reflections with the same frequency of interest and greater amplitude contaminate direct waves and thus compromise measurement of Lamb wave dispersion in different materials. In this study, non-reflecting boundaries were proposed in both numerical and experimental cases to facilitate time-frequency characterization of Lamb wave dispersion. First, the Lamb wave equations in isotropic and laminated materials were analytically solved. Second, the non-reflecting boundaries were used as a series of frames with gradually increased damping coefficients in finite element models to absorb waves at boundaries while avoiding wave reflections due to abrupt property changes of each frame. Third, damping clay was sealed at plate edges to reduce the boundary reflection in experimental test. Finally, the direct waves were subjected to the slant-stack and short-time Fourier transformations to calculate the dispersion curves of phase and group velocities, respectively. Both the numerical and experimental results suggest that the boundary reflections are effectively alleviated, and the dispersion curves generated by the time-frequency analysis are consistent with the analytical solutions, demonstrating that the combination of non-reflecting boundary and time-frequency analysis is a feasible and reliable scheme for characterizing Lamb wave dispersion in plate-like structures.

Key Words
Lamb wave dispersion; non-reflecting boundary; slant-stack transformation; short-time fourier transformation; classical laminated plate theory; plate-like structures

Address
Zijian Wang: Department of Dam Safety Management, Nanjing Hydraulic Research Institute, 225 Guangzhou Road, Nanjing, 210029, China
Pizhong Qiao: Department of Civil and Environmental Engineering, Washington State University, Sloan Hall 117, Pullman, WA, 99164-2910, USA
Binkai Shi: School of Mechanics and Materials, Hohai University, Nanjing, 210098, China

Abstract
In this inquisition, a passive damper namely Stockbridge Damper (SBD) has been introduced to the field of vibration control of Offshore Wind Turbine (OWT) to reduce the earthquake excitations. The dynamic responses of the structure have been analyzed for three recorded earthquakes and the responses have been assessed. To find an optimum SBD, the parameters of damper have been optimized using Response Surface Methodology (RSM) based on Box-Behnken Design (BBD) and Particle Swarm Optimization (PSO). The influence of the design variables of SBD such as the diameter of messenger cable, the length of messenger cable and logarithmic decrement of the damping has been investigated through response variables such as maximum displacement, RMS displacement and frequency amplitude of structure under an artificially generated white noise. After that, the structure with optimized and non-optimized damper has been analyzed with under the same earthquakes. Moreover, the comparative results show that the structure with optimized damper is 11.78%, 18.71%, 11.6% and 7.77%, 7.01%, 10.23% more effective than the structure with non-optimized damper with respect to the displacement and frequency response under the earthquakes. The results show that the SBD can obviously affect the characteristics of the vibration of the OWT and RSM based on BBD and PSO approach can provide an optimum damper.

Key Words
Stockbridge damper; vibration control; offshore wind turbine; response surface methodology; Box–Behnken design; particle swarm optimization; multiobjective optimization

Address
Mohammad S. Islam and Dookie Kim: Civil and Environmental Engineering, Kunsan National University, 558 Daehak-ro, Gunsan-si 54150, Republic of Korea
Jeongyun Do: Industry-University Cooperation Foundation, Kunsan National University, 558 Daehak-ro, Gunsan-si 54150, Republic of Korea

Abstract
E-Health allows you to supersede the central patient wireless healthcare system. Wireless Body Sensor Network (WBSN) is the first phase of the e-Health system. In this paper, we aim to understand e-Health architecture and configuration, and attempt to minimize energy consumption and latency in transmission routing protocols during restrictive latency in data delivery of WBSN phase. The goal is to concentrate on polling protocol to improve and optimize the routing time interval and schedule communication to reduce energy utilization. In this research, two types of network models routing protocols are proposed – elemental and clustering. The elemental model improves efficiency by using a polling protocol, and the clustering model is the extension of the elemental model that Destruct Supervised Decision Tree (DSDT) algorithm has been proposed to solve the time interval conflict transmission. The simulation study verifies that the proposed models deliver better performance than the existing BSN protocol for WBSN.

Key Words
Wireless Body Sensor Networks; e-Health; energy efficient routing protocol; polling protocol

Address
Kaebeh Yaeghoobi S.B., M.K. Soni and S.S. Tyagi: Faculty of Engineering and Technology, Manav Rachna International University, 121004 Haryana, India

Abstract
An efficient method utilizing the multi-stage improved differential evolution algorithm (MSIDEA) as an optimization solver is presented here to detect the multiple-damage of structural systems. Natural frequency changes of a structure are considered as a criterion for damage occurrence. The structural damage detection problem is first transmuted into a standard optimization problem dealing with continuous variables, and then the MSIDEA is utilized to solve the optimization problem for finding the site and severity of structural damage. In order to assess the performance of the proposed method for damage identification, an experimental study and two numerical examples with considering measurement noise are considered. All the results demonstrate the effectiveness of the proposed method for accurately determining the site and severity of multiple-damage. Also, the performance of the MSIDEA for damage detection compared to the standard differential evolution algorithm (DEA) is confirmed by test examples.

Key Words
damage detection; natural frequency; optimization method; multi-stage improved differential evolution algorithm; modal testing

Address
Seyed Mohammad Seyedpoor, Eshagh Norouzi and Sara Ghasemi: Department of Civil Engineering, Shomal University, Amol, Iran

Abstract
Many studies in risk management have been focused on management process, contract relation, and risk analysis in the past decade, but very few studies have addressed project risks from the perspective of risk efficiency. This study started with using Fault Tree Analysis to develop a framework for the decision-making support system of risk management from the perspective of risk efficiency, in order for the support system to find risk strategies of optimal combination for the project manager by the trade-off between project risk and cost of project strategies. Comprehensive and realistic risk strategies must strive for optimal decisions that minimize project risks and risk strategies cost while addressing important data such as risk causes, risk probability, risk impact and risk strategies cost. The risk management in the construction phase of building projects in Taiwan upon important data has been analyzed, that provided the data for support system to include 247 risk causes. Then, 17 risk causes were extracted to demonstrates the decision-making support system of risk management from the perspective of risk efficiency in building project of Taiwan which could reach better combination type of risk strategies for the project manager by the trade-off between risk cost and project risk.

Key Words
risk management; risk strategy; fault tree analysis; risk efficiency; decision-making support system(DSS)

Address
Tsung-Chieh Tsai: Department of Construction Engineering, National Yunlin University of Science & Technology, Taiwan
123 University Road, Section 3, Douliou, Yunlin 64002 Taiwan, R.O.C.
Hsiang-Wen Li: School of Engineering Science and Technology, National Yunlin University of Science & Technology,Taiwan 123 University Road, Section 3, Douliou, Yunlin 64002 Taiwan, R.O.C.




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