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CONTENTS
Volume 25, Number 4, November20 2017
 

Abstract
In this work, a new higher shear deformation theory (HSDT) is developed for the free vibration and buckling of functionally graded (FG) sandwich plates. The proposed theory presents a new displacement field by using undetermined integral terms. Only four unknowns are employed in this theory, which is less than the classical first shear deformation theory (FSDT) and others HSDTs. Equations of motion are obtained via Hamilton\'s principle. The analytical solutions of FG sandwich plates are determined by employing the Navier method. A good agreement between the computed results and the available solutions of existing HSDTs is found to prove the accuracy of the developed theory.

Key Words
buckling; vibration; sandwich plate; functionally graded materials; plate theory

Address
Mohamed Sekkal: 1Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria;
Laboratoire de Modélisation et Simulation Multi-échelle, Département de Physique, Faculté des Sciences Exactes,
Département de Physique, Université de Sidi Bel Abbés, Algeria
Bouazza Fahsi: 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: Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria;
Laboratoire de Modélisation et Simulation Multi-échelle, Département de Physique, Faculté des Sciences Exactes,
Département de Physique, Université de Sidi Bel Abbés, Algeria;
Laboratoire des Structures et Matériaux Avancés dans le Génie Civil et Travaux Publics, Université de Sidi Bel Abbes, Faculté de Technologie, Département de génie civil, Algeria
S.R. Mahmoud: Department of Mathematics, Faculty of Science, King Abdulaziz University, Saudi Arabia




Abstract
The fabric braided braking hose that delivers the driver\'s braking force to brake cylinder undergoes the large deformation cyclic motion according to the steering and bump/rebound motions of vehicle. The cyclic large deformation of braking hose may give rise to two critical problems: the interference with other adjacent vehicle parts and the micro cracking stemming from the fatigue damage accumulation. Hence, both the hose deformation and the fatigue damage become the critical issue in the design of braking hose. In this context, this paper introduces a multi-objective optimization method for minimizing the both quantities. The total length of hose and the helix angles of fabric braided composite layers are chosen for the design variables, and the maximum hose deformation and the critical fatigue life cycle are defined by the individual single objective functions. The trade-off between two single objective functions is made by introducing the weighting factors. The proposed optimization method is validated and the improvement of initial hose design is examined through the benchmark simulation. Furthermore, the dependence of optimum solutions on the weighting factors is also investigated.

Key Words
fabric braided rubber hose; cyclic motion; multi-objective optimization; durability and deformed layout; helix angle and hose length

Address
J.R. Cho: Department of Naval Architecture and Ocean Engineering, Hongik University, Sejong 339-701, Korea
Y.H. Kim: Graduate School of Mechanical Engineering, Pusan National University, Busan 609-735, Korea

Abstract
The thermo-mechanical vibration behavior of two dimensional functionally graded (2D-FG) porous nanobeam is reported in this paper. The material properties of the nanobeam are variable along thickness and length of the nanobeam according to the power law function. The nanobeam is modeled within the framework of Timoshenko beam theory. Eringen\'s s nonlocal elasticity theory is used to develop the governing equations. Using the generalized differential quadrature method (GDQM) the governing equations are solved. The effect of porosity, temperature distribution, nonlocal value, L/h, FG power indexes along thickness and length and are investigated using parametric studies.

Key Words
thermal vibration; Eringen theory; porous; imperfect nanobeam; 2D-FGM.

Address
Seyed Sajad Mirjavadi and A.M.S. Hamouda: Department of Mechanical and Industrial Engineering, Qatar University, P.O. Box 2713, Doha, Qatar
Behzad Mohasel Afshari: School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran
Navvab Shafiei: Department of Mechanical Engineering, Payame Noor University (PNU), P. O. Box, 19395-3697, Tehran, Iran
Mohammad Kazemi:Hoonam Sanat Farnak Engineering and Technology Company, Postal code: 6931876647, Ilam, Iran

Abstract
This paper presents unprecedented damped oscillation behaviours of a precast steel-concrete composite slab panel for track support. The steel-concrete composite slab track is an innovative slab track, a form of ballastless track which is becoming increasingly attractive to asset owners as they seek to reduce lifecycle costs and deal with increasing rail traffic speeds. The slender nature of the slab panel due to its reduced depth of construction makes it susceptible to vibration problems. The aim of the study is driven by the need to address the limited research available to date on the dynamic behaviour of steel-concrete composite slab panels for track support. Free vibration analysis of the track slab has been carried out using ABAQUS. Both undamped and damped eigenfrequencies and eigenmodes have been extracted using the Lancsoz method. The fundamental natural frequencies of the slab panel have been identified together with corresponding mode shapes. To investigate the sensitivity of the natural frequencies and mode shapes, parametric studies have been established, considering concrete strength and mass and steel\'s modulus of elasticity. This study is the world first to observe crossover phenomena that result in the inversion of the natural orders without interaction. It also reveals that replacement of the steel with aluminium or carbon fibre sheeting can only marginally reduce the natural frequencies of the slab panel.

Key Words
free vibration; steel-concrete composite; ballastless track; slab panel track; natural frequency; natural mode; mass; stiffness; crossover; veering

Address
Sakdirat Kaewunruen: Birmingham Centre for Railway Research and Education, School of Engineering, University of Birmingham, Birmingham B15 2TT UK
Stephen Kimindiri Kimani: Department of Civil Engineering, School of Engineering, University of Birmingham, Birmingham B15 2TT UK

Abstract
Many authors have established the usefulness of concrete filled steel tubular (CFST) sections as compression members while few have proved their utility as flexural members. To explore their prospective as part of CFST frame structures, two types of connections using extended end plate and seat angle are proposed for exterior joints of CFST beams and CFST columns. To investigate the performance and failure modes of the proposed bolted connections subjected to static loads, an experimental program has been executed involving ten specimens of exterior beam-to-column joints subjected to monotonically increasing load applied at the tip of beam, the performance is appraised in terms of load deformation behaviour of joints. The test parameters varied are the beam section type, type and diameter of bolts. To validate the experimental behaviour of the proposed connections in CFST beam-column joints, finite element analysis for the applied load has been performed using software ATENA-3D and the results of the proposed models are compared with experimental results. The experimental results obtained agree that the proposed CFST beam-column connections perform in a semi-rigid and partial strength mode as per specification of EC3.

Key Words
concrete filled steel tubular columns; extended end plate (connection); seat angle (connection); through bolts; monotonic loading

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

Abstract
The objective of this paper is to investigate the flexural behavior of concrete-filled round-ended steel tubes (CFRTs) under bending. Beam specimens were tested to investigate the mechanical behavior of the CFRTs, including four CFTs with different concrete strengths and steel ratios, and three CFRTs with varied aspect ratios. The load vs. deflection relationships and the failure modes for CFRTs were analyzed in detail. The composite action between the core concrete and steel tube was also discussed and examined based on the experimental results. In addition, ABAQUS program was used to develop the full-scale finite element model and analyze the effect of different parameters on the moment vs. curvature curves of the CFRTs bending about the major and minor axis, respectively. Furthermore, design formulas were proposed to estimate the ultimate moment and the flexural stiffness of the CFRTs, and the simplified theoretical model of the moment vs. curvature curves was also developed. The predicted results showed satisfactory agreement with the experimental and FE results. Finally, the differences of the experimental, FE and predicted results using the existing codes were illustrated.

Key Words
concrete-filled round-ended steel tube (CFRT); flexural behavior; ultimate moment; finite element analysis; full-scale model; composite action

Address
Fa-xing Ding, Tao Zhang, Liping Wang and Lei Fu: School of Civil Engineering, Central South University, Changsha, Hunan Province, 410075, P.R. China

Abstract
In this study a seismic retrofit scheme for a building structure was presented using steel plate slit dampers. The energy dissipation capacity of the slit damper used in the retrofit was verified by cyclic loading test. Genetic algorithm was applied to find out the optimum locations of the slit dampers satisfying the target displacement. The seismic retrofit of the model structure using the slit dampers was compared with the retrofit with enlarging shear walls. A simple damper distribution method was proposed using the capacity spectrum method along with the damper distribution pattern proportional to the inter-story drifts. The validity of the simple story-wise damper distribution procedure was verified by comparing the results of genetic algorithm. It was observed that the capacity-spectrum method combined with the simple damper distribution pattern leaded to satisfactory story-wise distribution of dampers compatible with the optimum solution obtained from genetic algorithm.

Key Words
seismic retrofit; slit dampers; optimum design; genetic algorithm; capacity spectrum method

Address
Jinkoo Kim, Minjung Kim and Mohamed Nour Eldin: Department of Civil and Architectural Engineering, Sungkyunkwan University, Suwon, Korea

Abstract
In this paper, damage detection has been introduced as an optimization problem and a two-step method has been proposed that can detect the location and severity of damage in truss structures precisely and reduce the volume of computations considerably. In the first step, using the residual force vector concept, the suspected damaged members are detected which will result in a reduction in the number of variables and hence a decrease in the search space dimensions. In the second step, the precise location and severity of damage in the members are identified using the genetic algorithm and the results of the first step. Considering the reduced search space, the algorithm can find the optimal points (i.e. the solution for the damage detection problem) with less computation cost. In this step, the Efficient Correlation Based Index (ECBI), that considers the structure\'s first few frequencies in both damaged and healthy states, is used as the objective function and some examples have been provided to check the efficiency of the proposed method; results have shown that the method is innovatively capable of detecting damage in truss structures.

Key Words
damage detection; residual force vector; genetic algorithm; optimization; modal frequency; mode shape

Address
Mehdi Nobahari and Mohammad Reza Ghasemi: Department of Civil Engineering, University of Sistan and Baluchestan, Zahedan, Iran
Naser Shabakhty: School of Civil Engineering, Iran University of Science and Technology, Tehran, Iran

Abstract
In this paper, nonlinear vibration of multi-degree of freedom systems are studied. It has been tried to develop the mathematical model of systems by second-order nonlinear partial differential equations. The masses are connected with linear and nonlinear springs in series. A great effort has been done to solve the nonlinear governing equations analytically. A new analytical method called Variational Iteration Method (VIM) is proposed and successfully applied to the problem. The linear and nonlinear frequencies are obtained and the results are compared with numerical solutions. The first order of Variational Iteration Method (VIM) leads us to high accurate solution.

Key Words
nonlinear vibration; two-degree-of-freedom; Variational Iteration Method (VIM)

Address
Mahmoud Bayat: Young Researchers and Elite Club, Roudehen Branch, Islamic Azad University, Roudehen, Iran
Iman Pakar: Young Researchers and Elite club, Mashhad Branch, Islamic Azad University, Mashhad, Iran
Mahdi Bayat: Department of Civil Engineering, Roudehen Branch, Islamic Azad University, Roudehen, Iran

Abstract
The steel plate shear wall with beam-only connected infill plate (SSW-BO) is an innovative lateral load resisting system consisting of infill plates connected to surrounding beams and separated from the main columns. In this research, the effects of perforation diameter as well as slenderness ratios of infill plates on the hysteresis behavior of SSW-BO systems were studied experimentally. Experimental testing is performed on eight one-sixth scaled one-story SSW-BO specimens with two plate thicknesses and four different circular opening ratios at the center of the panels under fully reversed cyclic quasi-static loading in compliance with the SAC test protocol. Strength, stiffness, ductility and energy absorption were evaluated based on the hysteresis loops. It is found that the systems exhibited stable hysteretic behavior during testing until significant damage in the connection of infill plates to surrounding beams at large drifts. It is also seen that pinching occurred in the hysteresis loops, since the hinge type connections were used as boundaries at four corners of surrounding frames. The strength and initial stiffness degradation of the perforated specimens containing opening ratio of 0.36 compared to the solid one is in the range of 20% to 30% and 40% to 50%, respectively.

Key Words
steel shear wall with beam-only connected infill plate (SSW-BO); analytical method; cyclic loading; hysteresis; dissipated energy

Address
Behzad Shekastehband and Ali A. Azaraxsh: Department of Civil Engineering, Urmia University of Technology, Urmia, Iran
Hossein Showkati: Department of Civil Engineering, University of Urmia, Urmia, Iran


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