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CONTENTS
Volume 56, Number 3, November10 2015
 

Abstract
The dual-phase lag heat transfer model is employed to study the problem of isotropic generalized thermoelastic medium with internal heat source. The normal mode analysis is used to obtain the exact expressions for displacement components, force stress and temperature distribution. The variations of the considered variables through the horizontal distance are illustrated graphically. The results are discussed and depicted graphically.

Key Words
dual-phase-lag model; thermoelasticity; temperature distribution; normal-mode

Address
Praveen Ailawalia: Department of Applied Sciences, MM University, Sadopur, Ambala City, Haryana, India

Amit Singla: Department of Mathematics, Baba Banda Singh Bahadur Engineering College, Fatehgarhsahib, Punjab, India

Abstract
This paper deals with a new designed joint system for single-layer spatial structures. As the stability of these structures is greatly influenced by the joint behaviour, the aim of this paper is the characterization of the joint response in bending through Finite Element Method (FEM) analysis using ABAQUS. The behaviour of the joints studied here was influenced by many geometrical factors, such as bolts and plate sizes, distance between bolts and end-plate thickness. The study comprised five models of joints with different values of those parameters. The numerical results were compared to the results of previous experimental tests and the agreement was good enough. The differences between the numerical and experimental initial stiffness are attributed to the simplifications introduced when modelling the bolt threads as well as the presence of residual stresses in the test specimens.

Key Words
joint-rigidity; single-layer structures; finite element method; nonlinear analysis; bolt connection;ABAQUS

Address
A. Lopez- Arancibia, A.M. Altuna-Zugasti and A. Pradera-Mallabiabarrena: Department of Mechanical Engineering, Institute of Civil Engineering, Tecnun (University of Navarra), Manuel de Lardizábal 13, 20018 San Sebastián, Spain

H. Aizpurua Aldasoro:Institute of Steel Structures, Technische Universität Carolo-Wilhelmina Braunschweig, Beethovenstr. 51, 38106, Braunschweig, Germany

Abstract
In this study, effect of various material hardening models based on Holloman\'s isotropic, Ziegler\'s linear kinematic, non-linear kinematic and mixture of the isotropic and nonlinear kinematic hardening laws on springback prediction of titanium alloy (Ti-3Al-2.5V) in a tube rotary draw bending (RDB) process was investigated with presenting the keynotes for a comprehensive step by step ABAQUS simulation. Influence of mandrel on quality of the final product including springback, wall-thinning and cross-section deformation of the tube was investigated, too. Material parameters of the hardening models were obtained based on information of a uniaxial test. In particular, in the case of combined iso-nonlinear kinematic hardening the material constants were calibrated by a simple approach based on half-cycle data instead of several stabilized cycles ones. Moreover, effect of some material and geometrical parameters on springback was carried out. The results showed that using the various hardening laws separately cannot describe the material hardening behavior correctly. Therefore, it is concluded that combining the hardening laws is a good idea to have accurate springback prediction. Totally the results are useful for predicting and controlling springback and cross-section deformation in metal forming processes.

Key Words
springback; cross-section deformation; metal forming; finite element method; tube bending; andrel

Address
Mehdi Shahabia and Ali Nayebi: Department of Mechanical Engineering, Shiraz University, Shiraz, Mollasadra Street, Iran

Abstract
This paper deals with the problem of the global stabilization for a class of tension leg platform (TLP) nonlinear control systems. It is well known that, in general, the global asymptotic stability of the TLP subsystems does not imply the global asymptotic stability of the composite closed-loop system. Finding system parameters for stabilizing the control system is also an issue need to be concerned. In this paper, we give additional sufficient conditions for the global stabilization of a TLP nonlinear system. In particular, we consider a class of NN based Takagi-Sugeno (TS) fuzzy TLP systems. Using the so-called parallel distributed compensation (PDC) controller, we prove that this class of systems can be globally asymptotically stable. The proper design of system parameters are found by a swarm intelligence algorithm called Evolved Bat Algorithm (EBA). An illustrative example is given to show the applicability of the main result.

Key Words
linear matrix inequality; automated design; fuzzy logic model and control; Evolved Bat Algorithm

Address
Pei-Wei Tsai: College of Information Science and Engineering, Fujain University of Technology, Fuzhou, China
T. Hayat: Department of Mathematics, Quaid-I-Azam University 45320, Islamabad 44000, Pakistan
B. Ahmad: Nonlinear Analysis and Applied Mathematics (NAAM) Research Group, Department of Mathematics,
Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia
Cheng-Wu Chen: Department of Maritime Information and Technology, National Kaohsiung Marine University,
Kaohsiung, Taiwan, R.O.C.

Abstract
In this paper, the Multi-Swarm Fruit Fly Optimization Algorithm (MFOA) is presented for structural damage identification using the first several natural frequencies and mode shapes. We assume damage only leads to the decrease of element stiffness. The differences on natural frequencies and mode shapes of damaged and intact state of a structure are used to establish the objective function, which transforms a damage dentification problem into an optimization problem. The effectiveness and accuracy of MFOA are demonstrated by three different structures. Numerical results show that the MFOA has a better capacity for structural damage identification than the original Fruit Fly Optimization Algorithm (FOA) does.

Key Words
damage identification; multi-swarm fruit fly optimization algorithm; non-destructive techniques; frequency domain

Address
S. Li and Z.R. Lu: damage identification; multi-swarm fruit fly optimization algorithm; non-destructive techniques; frequency domain

Abstract
This study examines the wavelet transform for output-only system identification of ambient excited engineering structures with emphasis on its utilization for modal parameter estimation of high-order and closely-spaced modes. Sophisticated time-frequency resolution analysis has been carried out by employing the modified complex Morlet wavelet function for better adaption and flexibility of the timefrequency resolution to extract two closely-spaced frequencies. Furthermore, bandwidth refinement techniques such as a bandwidth resolution adaptation, a broadband filtering technique and a narrowband filtering one have been proposed in the study for the special treatments of high-order and closely-spaced modal parameter estimation. Ambient responses of a 5-story steel frame building have been used in the numerical example, using the proposed bandwidth refinement techniques, for estimating the modal parameters of the high-order and closely-spaced modes. The first five natural frequencies and damping ratios of the structure have been estimated; furthermore, the comparison among the various proposed bandwidth refinement techniques has also been examined.

Key Words
output-only system identification; modal parameter estimation; wavelet transform; high-order and closely-spaced modes; steel building; time-frequency resolution analysis; narrowband filtering; broadband filtering

Address
Thai-Hoa Leand Luca Caracoglia1a: Department of Civil and Environmental Engineering, Northeastern University, 360 Huntington Ave., Boston, MA 02115, USA

Abstract
This paper presents the analysis of mechanical behavior of metal wall panels of storehouses and industrial buildings subjected to differential settlements. The storehouses considered are representative of those used in the agricultural activity. A small-scale model was built and tested in order to have evidence of the behavior and to validate computational models. The numerical investigation is carried out through finite element analysis using a general-purpose software, by modeling buildings with different geometries and evaluating different settlements of the ground. To obtain an adequate model, geometric non-linearity has to be taken into account. Models that represent the most usual geometric typologies were investigated under support settlements. The deflected shape of the wall panel and the relationship between the horizontal displacements and the settlement of the foundations are evaluated. The results show that there are large outof-plane displacements caused by settlements that would be admitted by design recommendations.

Key Words
buckling; differential settlements; finite elements; industrial buildings; storehouses; wall metal panels

Address
Suyai Fernández1a: Intertechne Consultores y Asociados, 8300 Neuquén, Argentina
Rossana C. Jaca: Civil Engineering Department, National University of Comahue, 8300 Neuquén, Argentina
Luis A. Godoy: Institute for Advanced Studies in Engineering and Technology, IDIT CONICET-UNC, and FCEFyN, Universidad Nacional de Córdoba, PO Box 916, 5000 Córdoba, Argentina



Abstract
In this paper, the nonlinear static response of curled cantilever beam actuators subjected to the one-sided electrostatic field is focused on. By assuming the deflection function of electrostatically actuated beam, analytical approximate solutions are established via using Galerkin method to solve the equilibrium equation. The Pull-In voltages which determine the stability of the curled beam actuators are also obtained.These approximate solutions show excellent agreements with numerical solutions obtained by the shooting method and the experimental data for a wide range of beam length. Expressions of these analytical approximate solutions are brief and could easily be used to derive the effects of various physical parameters on MEMS structures.

Key Words
MEMS; Galerkin method; large deformation; analytical approximation

Address
Youhong Suna, Yongping Yu and Baochang Liub: College of Construction Engineering, Jilin University, Changchun 130026, P.R. China

Abstract
This paper presents the analysis of intermediate crack-induced (IC) debonding failure loads for reinforced concrete (RC) beams strengthened with adhesively-bonded fiber-reinforced polymer (FRP) plates or sheets. The analysis consists of the energy release and simple ACI methods. In the energy release method, a fracture criterion is employed to predict the debonding loads. The interfacial fracture energy that indicates the resistance to debonding is related to the bond-slip relationships obtained from the shear test of FRP-toconcrete bonded joints. The section analysis that considers the effect of concrete‟s tension stiffening is employed to develop the moment-curvature relationships of the FRP-strengthened sections. In the ACI method, the onset of debonding is assumed when the FRP strain reaches the debonding strain limit. The tension stiffening effect is neglected in developing a moment-curvature relationship. For a comparison purpose, both methods are used to numerically investigate the effects of relevant parameters on the IC debonding failure loads. The results show that the debonding failure load generally increases as the concrete compressive strength, FRP reinforcement ratio, FRP elastic modulus and steel reinforcement ratio increase.

Key Words
fiber-reinforced polymers; strengthening; reinforced concrete beams; intermediate crackinduced debonding; bond-slip relationships; fracture mechanics

Address
Peelak Wantanasiria and Akhrawat Lenwari: Department of Civil Engineering, Faculty of Engineering, Chulalongkorn University,
Phayathai Road, Pathumwan, Bangkok, Thailand 10330

Abstract
Propagation of the generalized Rayleigh waves in an initially stressed elastic half-space covered by an elastic layer is investigated. It is assumed that the initial stresses are caused by the uniformly distributed normal compressional forces acting on the face surface of the covering layer. Two different cases where the compressional forces are \"dead\" and \"follower\" forces are considered. Three-dimensional linearized theory of elastic waves in initially stressed bodies in plane-strain state is employed and the elasticity relations of the materials of the constituents are described through the Murnaghan potential where the influence of the third order elastic constants is taken into consideration. The dispersion equation is derived and an algorithm is developed for numerical solution to this equation. Numerical results for the dispersion of the generalized Rayleigh waves on the influence of the initial stresses and on the influence of the character of the external compressional forces are presented and discussed. These investigations provide some theoretical foundations for study of the near-surface waves propagating in layered mechanical systems with a liquid upper layer, study of the structure of the soil of the bottom of the oceans or of the seas and study of the behavior of seismic surface waves propagating under the bottom of the oceans.

Key Words
generalized Rayleigh wave; initial stresses; dead forces; follower forces; wave dispersion; third order elasticity constants

Address
Masoud Negin: Department of Earthquake Engineering, Istanbul Technical University, Ayazaga Campus, 34469 Maslak, Istanbul, Turkey


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