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CONTENTS
Volume 19, Number 4, April 2017
 

Abstract
Based on the super elastic properties of the shape memory alloy (SMA) and the inverse piezoelectric effect of piezoelectric (PZT) ceramics, a kind of hybrid semi-active control device was designed and made, its mechanical properties test was done under different frequency and different voltage. The local search ability of genetic algorithm is poor, which would fall into the defect of prematurity easily. A kind of adaptive immune memory cloning algorithm(AIMCA) was proposed based on the simulation of clone selection and immune memory process. It can adjust the mutation probability and clone scale adaptively through the way of introducing memory cell and antibody incentive degrees. And performance indicator based on the modal controllable degree was taken as antigen-antibody affinity function, the optimization analysis of damper layout in a space truss structure was done. The structural seismic response was analyzed by applying the neural network prediction model and T-S fuzzy logic. Results show that SMA and PZT friction composite damper has a good energy dissipation capacity and stable performance, the bigger voltage, the better energy dissipation ability. Compared with genetic algorithm, the adaptive immune memory clone algorithm overcomes the problem of prematurity effectively. Besides, it has stronger global searching ability, better population diversity and faster convergence speed, makes the damper has a better arrangement position in structural dampers optimization leading to the better damping effect.

Key Words
SMA and PZT; composite damper; hybrid semi-active control; mechanical test; memory unit; antibody incentive degrees

Address
Meng Zhan, Sheliang Wang, Tao Yang and Binshan Yu: Department of Civil Engineering, Xi\'an University of Architecture and Technology, No.13 Yanta RD., Xi\'an, Shaanxi 710055, PR China
Yang Liu: Department of Civil Engineering, Xi\'an University of Architecture and Technology, No.13 Yanta RD., Xi\'an, Shaanxi 710055, PR China;
Key Laboratory of Green Building in West China, Xi\'an University of Architecture and Technology,
No.13 Yanta RD., Xi\'an, Shaanxi 710055, PR China;
School of Civil Engineering and Geodesy,Shaanxi College of Communication Technology,
No.19 Wenjing RD., Xi\'an, Shaanxi 710018, PR China


Abstract
Protection of structures against natural hazards such as earthquakes has always been a major concern. Semi-active control combines the reliability of passive control and versatility and adaptability of active control. So it has recently become a preferred control method. This paper proposes an algorithm based on Uniform Deformation Theory to mitigate vulnerable buildings using magneto-rheological (MR) damper. Due to the successful performance of fuzzy logic in control of systems and its simplicity and intrinsically robustness, it is used here to regulate MR dampers. The particle swarm optimization (PSO) algorithm is also used as an adaptive method to develop a fuzzy control algorithm that is able to create uniform inter-story drifts. Results show that the proposed algorithm exhibited a desirable performance in reducing both linear and nonlinear seismic responses of structures. Performance of the presented method is indicated in compare with passive-on and passive-off control algorithms.

Key Words
semi-active control; fuzzy system; MR damper; Uniform Deformation Theory; particle swarm optimization algorithm

Address
Department of civil engineering, K. N. Toosi University of Technology, No. 1346, Vali Asr Street, Mirdamad Intersection, Tehran, Iran


Abstract
Electromechanical impedance method as an efficient tool in Structural Health Monitoring (SHM) utilizes the electromechanical impedance of piezoelectric materials which is directly related to the mechanical impedance of the host structure and will be affected by damages. In this paper, electromechanical impedance of piezoelectric patches attached to simply support rectangular plate is determined theoretically and experimentally in order to detect damage. A pairs of piezoelectric wafer active sensor (PWAS) patches are used on top and bottom of an aluminum plate to generate pure bending. The analytical model and experiments are carried out both for undamaged and damaged plates. To validate theoretical models, the electromechanical impedances of PWAS for undamaged and damaged plate using theoretical models are compared with those obtained experimentally. Both theoretical and experimental results demonstrate that by crack generation and intensifying this crack, natural frequency of structure decreases. Finally, in order to evaluate damage severity, damage metrics such as Root Mean Square Deviation (RMSD), Mean Absolute Percentage Deviation (MAPD), and Correlation Coefficient Deviation (CCD) are used based on experimental results. The results show that generation of crack and crack depth increasing can be detectable by CCD.

Key Words
electromechanical impedance method; Structural Health Monitoring; damage index; crack intensity; thin plate; modeling; experiments

Address
Mehdi Rajabi, Mahyar Naraghi: Department of Mechanical Engineering, Amirkabir University of Technology, Tehran, Iran

Mehdi Rajabi, Mahnaz Shamshirsaz: New Technologies Research Center, Amirkabir University of Technology, Tehran, Iran

Abstract
Concrete filled steel tubes are extensively applied in engineering structures due to their resistance to high tensile and compressive load and convenience in construction. But one major flaw, their vulnerability to environmental attack, can severely reduce the strength and life of these structures. Degradation due to corrosion of steel confining the concrete is one of the major durability problems faced by civil engineers to maintain these structures. The problem accelerates as inner surface of steel tube is in contact with concrete which serves as electrolyte. If it remains unnoticed, it further accelerates and can be catastrophic. This paper discusses a non-destructive degradation monitoring technique for early detection corrosion in steel tubes in CFST members. Due to corrosion, damage in the form of debonding and pitting occurs in steel sections. Guided ultrasonic waves have been used as a feasible and attractive solution for the detection and monitoring of corrosion damages in CFST sections. Guided waves have been utilized to monitor the effect of notch and debond defects in concrete filled steel tubes simulating pitting and delamination of steel tubes from surrounding concrete caused by corrosion. Pulse transmission has been used to monitor the healthy and simulated damaged specimens. A methodology is developed and successfully applied for the monitoring of concrete filled steel tubular sections undergoing accelerated chloride corrosion. The ultrasonic signals efficiently narrate the state of steel tube undergoing corrosion.

Key Words
guided waves; corrosion; notching; delamination; concrete filled steel tubular sections

Address
Kumari Beena, Sharma Shruti, Kwatra Naveen: Department of Civil Engineering, Thapar University, Patiala 147-001, India

Sharma Sandeep: Department of Mechanical Engineering, Thapar University, Patiala 147-001, India


Abstract
In this paper, we investigate the impacts of network topology on the performance of a distributed estimation algorithm, namely combine- then-adaptive (CTA) diffusion LMS, based on the data with or without the assumptions of temporal and spatial independence with noisy links. The study covers different network models, including the regular, small-world, random and scale-free whose the performance is analyzed according to the mean stability, mean-square errors, communication cost (link density) and robustness. Simulation results show that the noisy links do not cause divergence in the networks. Also, among the networks, the scale free network (heterogeneous) has the best performance in the steady state of the mean square deviation (MSD) while the regular is the worst case. The robustness of the networks against the issues like node failure and noisier node conditions is discussed as well as providing some guidelines on the design of a network in real condition such that the qualities of estimations are optimized.

Key Words
complex networks; adaptive networks; diffusion mode; distributed estimation; LMS algorithm

Address
Department of Electrical Engineering, Sahand university of technology, Tabriz, Iran

Abstract
Many vibration-based global damage detection methods attempt to extract modal parameters from vibration signals as the main structural features to detect damage. The local flexibility method is one promising method that requires only the first few fundamental modes to detect not only the location but also the extent of damage. Generally, the mode shapes in the lateral degree of freedom are extracted from lateral vibration signals and then used to detect damage for a beam structure. In this study, a new approach which employs the mode shapes in the rotary degree of freedom obtained from the macro-strain vibration signals to detect damage of a beam structure is proposed. In order to facilitate the application of mode shapes in the rotary degree of freedom for beam structures, the local flexibility method is modified and utilized. The proposed rotary approach is verified by numerical and experimental studies of simply supported beams. The results illustrate potential feasibility of the proposed new idea. Compared to the method that uses lateral measurements, the proposed rotary approach seems more robust to noise in the numerical cases considered. The sensor configuration could also be more flexible and customized for a beam structure. Primarily, the proposed approach seems more sensitive to damage when the damage is close to the supports of simply supported beams.

Key Words
local flexibility method; macro-strain; long gauge; beam structure; damage detection

Address
Ting Yu Hsu: Department of Civil and Construction Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan

Wen I Liao: Department of Civil and Environment Engineering, National Taipei University of Technology, Taipei, Taiwan

Ting Yu Hsu, Shen Yau Hsiao: National Center for Research on Earthquake Engineering, Taipei, Taiwan

Abstract
The present article encompasses a nonlinear finite element (FE) and genetic algorithm (GA) based optimal vibration energy harvesting from nonprismatic piezo-laminated cantilever beams. Three cases of cross section profiles (such as linear, parabolic and cubic) are modelled to analyse the geometric nonlinear effects on the output responses such as displacement, voltage, and power. The simultaneous effects of taper ratios (such as breadth and height taper) on the output power are also studied. The FE based nonlinear dynamic equation of motion has been solved by an implicit integration method (i.e., Newmark method in conjunction with the Newton-Raphson method). Besides this, a real coded GA based constrained optimization scheme has also been proposed to determine the best set of design variables for optimal harvesting of power within the safe limits of beam stress and PZT breakdown voltage.

Key Words
geometric nonlinearity; piezoelectricity; nonprismatic beam; finite element; genetic algorithm; optimal energy harvesting

Address
Department of Mechanical Engineering, National Institute of Technology Rourkela, Rourkela-769008, Odisha, India

Abstract
This paper focuses on the impact of the wave passage effect on the long-span bridge. In order to make the wave passage effect more obvious, ground motion samples are selected from the near-fault ground motion of the 1999 Chi-Chi earthquake and an arch bridge with a 280m main span is selected as a bridge sample. The motion ground samples are divided into two groups according to the characteristics of near-fault. A sequence of fragility curves is developed. It is shown that the seismic damage is increased by the wave passage effect and the increase is more obvious in the near-fault ground motion.

Key Words
wave passage effect; near-fault ground motion; seismic fragility; concrete-filled steel tube arch bridges

Address
School of Civil Engineering, Dalian University of Technology, Dalian, 116024, China

Abstract
This investigation is aimed to develop a model of experimental-computation determination of a support moment of a cantilever beam loaded with concentrated force at its end including the optimal choice of coordinates of deflection data points and parameters of transformation of deflection data in case of insufficient accuracy of the assignment of initial parameters (support settlement, angle of rotation of the bearing section) and cantilever beam length. The influence of distribution and characteristics of sensors on the cantilever beam on the accuracy of determining the support moment which improves in the course of transition from the uniform distribution of sensors to optimal non-uniform distribution is shown. On the basis of the theory of inverse problems the method of transformation reduction at numerical differentiation of deflection functions has been studied. For engineering evaluation formulae of uncertainty estimate to determine a support moment of a cantilever beam at predetermined uncertainty of measurements using sensors have been obtained.

Key Words
cantilever beam; support moment; inverse problem; numerical differentiation; approximation; sensor; measurement uncertainty; condition number

Address
Department of Mechanics and Engineering, Southwest State University, 50 let Octobrya, 94, Kursk, 305040, Russia

Abstract
This paper uses the four-variable refined plate theory for the free vibration analysis of functionally graded material (FGM) rectangular plates. The plate properties are assumed to be varied through the thickness following a simple power law distribution in terms of volume fraction of material constituents. The theory presented is variationally consistent, does not require shear correction factor, and gives rise to transverse shear stress variation such that the transverse shear stresses vary parabolically across the thickness satisfying shear stress free surface conditions. Equations of motion are derived from the Hamilton

Key Words
Navier´s solutions; functionally graded material (FGM); free vibration; theoretical formulation

Address
Departement de Genie Civil, Universite Ibn Khaldoun, BP 78 Zaaroura, 14000 Tiaret, Algerie

Laboratoire des Materiaux & Hydrologie, Universite de Sidi Bel Abbes, 22000 Sidi Bel Abbes, Algerie


Abstract
One of the most recent methods of structural damage identification is using the difference between structures responses after and before damage occurrence. To do this one can formulate the damage detection problem as an inverse optimization problem where the extents of damage in each element are considered as the optimizations variables. To optimize the objective function, heuristic methods such as GA, PSO etc. are widely utilized. In this paper, inspired by animals such as bat, dolphin, oilbird, shrew etc. that use echolocation for finding food, a new and efficient method, called Echolocation Search Algorithm (ESA), is proposed to properly identify the site and extent of multiple damage cases in structural systems. Numerical results show that the proposed method can reliably determine the location and severity of multiple damage cases in structural systems.

Key Words
damage detection; modal frequency; inverse problem; optimization algorithm; echolocation search algorithm

Address
Mehdi Nobahari, Mohammad Reza Ghasemi: Department of Civil Engineering, University of Sistan and Baluchestan, Zahedan, Iran

Naser Shabakhty: School of Civil Engineering, University of Science and Technology, Tehran, Iran



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