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CONTENTS
Volume 51, Number 2, July25 2014
 

Abstract
The present investigation is concerned with the effect of two temperatures on functionally graded (FG) nanobeams subjected to sinusoidal pulse heating sources. Material properties of the nanobeam are assumed to be graded in the thickness direction according to a novel exponential distribution law in terms of the volume fractions of the metal and ceramic constituents. The upper surface of the FG nanobeam is fully ceramic whereas the lower surface is fully metal. The generalized two-temperature nonlocal theory of thermoelasticity in the context of Lord and Shulman\'s (LS) model is used to solve this problem. The governing equations are solved in the Laplace transformation domain. The inversion of the Laplace transformation is computed numerically using a method based on Fourier series expansion technique. Some comparisons have been shown to estimate the effects of the nonlocal parameter, the temperature discrepancy and the pulse width of the sinusoidal pulse. Additional results across the thickness of the nanobeam are presented graphically.

Key Words
thermoelasticity; two temperatures; FG nanobeam; nonlocal theory; sinusoidal pulse

Address
Ashraf M. Zenkour : Department of Mathematics, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia, Department of Mathematics, Faculty of Science, Kafrelsheikh University, Kafr El-Sheikh 33516, Egypt
Ahmed E. Abouelregal : Department of Mathematics, Faculty of Science, Mansoura University, Mansoura 35516, Egypt, Department of Mathematics, College of Science and Arts, University of Aljouf, El-Qurayat, Saudi Arabia

Abstract
Traditional beam connections to the minor axis of a column have relatively low strength and stiffness. A modified detail, using a plate welded between the toes of the column flange - referred to as a toe plate connection - is examined in this paper. The results of an experimental investigation for both flush and extended end-plate connections connected to a 25 mm thick end-plate are presented. The tests are complemented by finite element modelling which compares very well with the test observations. The results show a significant increase in both moment resistance and initial stiffness for this connection detail compared with connections made directly to the column web. This offers the prospect of more optimal solutions taking advantage of partial strength frame design for the minor axis as well as major axis.

Key Words
flush end-plate connection; extended end-plate connection; minor axis; partial strength; finite element analysis

Address
Mahmood M. Tahir, Mohd Y. Ishak, Shahrin Mohammad, Abdullah Z. Awang : UTM Construction Research Centre (UTM CRC), Faculty of Civil Engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor, Malaysia
Irwan Juki : Faculty of Civil Engineering, Universiti Tun Hussein Onn, Beg Berkunci 101, Parit Raja, 86400 Batu Pahat, Johor, Malaysia
Roger Plank : University of Sheffield, Western Bank, Sheffield, South Yorkshire S10 2TN, UK

Abstract
In this paper, the development of a new optimization software for finite element model updating of engineering structures titled as FemUP is described. The program is used for computational FEM model updating of structures depending on modal testing results. This paper deals with the FE model updating procedure carried out in FemUP. The theoretical exposition on FE model updating and optimization techniques is presented. The related issues including the objective function, constraint function, different residuals and possible parameters for FE model updating are investigated. The issues of updating process adopted in FemUP are discussed. The ideas of optimization to be used in FE model updating application are explained. The algorithm of Sequential Quadratic Programming (SQP) is explored which will be used to solve the optimization problem. The possibilities of the program are demonstrated with a three dimensional steel frame model. As a result of this study, it can be said that SQP algorithm is very effective in model updating procedure.

Key Words
finite element model updating; optimization; experimental modal analysis; operational modal analysis; SignalCAD; ModalCAD; FemUP; MATLAB; SQP algorithm

Address
Abdurrahman Şahin : Civil Engineering, Yildiz Technical University, Esenler, Istanbul 34220, Turkey
Alemdar Bayraktar : Civil Engineering, Karadeniz Technical University, Trabzon 61080, Turkey

Abstract
The mechanical characteristics of materials are very essential in structural analysis for the accuracy of structural calculations. The estimation modulus of elasticity of concrete (Ec), one of the most important mechanical characteristics, is a very complex area in terms of analytical models. Many attempts have been made to model the modulus of elasticity through the use of experimental data. In this study, the neuro-fuzzy (NF) technique was investigated in estimating modulus of elasticity of concrete and a new simple NF model by implementing a different NF system approach was proposed. A large experimental database was used during the development stage. Then, NF model results were compared with various experimental data and results from several models available in related research literature. Several statistic measuring parameters were used to evaluate the performance of the NF model comparing to other models. Consequently, it has been observed that NF technique can be successfully used in estimating modulus of elasticity of concrete. It was also discovered that NF model results correlated strongly with experimental data and indicated more reliable outcomes in comparison to the other models.

Key Words
concrete; elastic modulus; fuzzy logic; neuro-fuzzy systems

Address
İdris Bedirhanoglu : Department of Civil Engineering, Dicle University, 21280, Diyarbakir, Turkey

Abstract
Wharfs are essential to shipping and support very large gravity loads on both a short-term and long-term basis which cause quite large seismic internal forces. Therefore, these structures are vulnerable to seismic activities. As they are supported on vertical and/or batter piles, soil-pile interaction effects under earthquake events have a great importance in seismic resistance which is not yet fully understood. Seismic design codes have become more stringent and suggest the use of new design methods, such as Performance Based Design principles. According to Turkish Code for Coastal and Port Structures (TCCS 2008), the interaction between soil and pile should somehow be considered in the nonlinear analysis in an accurate manner. This study aims to explore the lateral load carrying capacity of recently designed wharf structures considering soil-pile interaction effects for different soil conditions. For this purpose, nonlinear structure analysis according to TCCS (2008) has been performed comparing simplified and detailed modeling results.

Key Words
pile-wharf structures; nonlinear soil springs; equivalent length, pushover analysis

Address
Bilge Doran and Aytuğ Seckin : Department of Civil Engineering, Yildiz Technical University, 34220 Esenler, İstanbul, Turkey

Abstract
Since the isolation bearings undergo large displacements in base-isolated structures, impact with adjacent structures is inevitable. Therefore, in this investigation, the effect of impact on seismic response of isolated structures mounted on double concave friction pendulum (DCFP) bearings subjected to near field ground motions is considered. A non-linear viscoelastic model of collision is used to simulate structural pounding more accurately. 2-, 4- and 8-story base-isolated buildings adjacent to fixed-base structures are modeled and the coupled differential equations of motion related to these isolated systems are solved in the MATLAB environment using the SIMULINK toolbox. The variation of seismic responses such as base shear, displacement in the isolation system and superstructure (top floor) is computed to study the impact condition. Also, the effects of variation of system parameters: isolation period, superstructure period, size of seismic gap between two structures, radius of curvature of the sliding surface and friction coefficient of isolator are contemplated in this study. It is concluded that the normalized base shear, bearing and top floor displacement increase due to impact with adjacent structure. When the distance between two structures decreases, the base shear and displacement increase comparing to no impact condition. Besides, the increase in friction coefficient difference also causes the normalized base shear and displacement in isolation system and superstructure increase in comparison with bi-linear hysteretic behavior of base isolation system. Totally, the comparison of results indicates that the changes in values of friction coefficient have more significant effects on 2-story building than 4- and 8-story buildings.

Key Words
double concave friction pendulum; isolation period; radius of curvature; friction coefficient; impact; near-field ground motions

Address
Morteza Bagheri and Faramarz Khoshnoudian : Department of Civil Engineering, Amirkabir University of Technology, Hafez St., Tehran, Iran

Abstract
In the first part of this paper, the influences of some of crack parameters on natural frequencies of a cracked cantilever Functionally Graded Beam (FGB) are studied. A cantilever beam is modeled using Finite Element Method (FEM) and its natural frequencies are obtained for different conditions of cracks. Then effect of variation of depth and location of cracks on natural frequencies of FGB with single and multiple cracks are investigated. In the second part, two Multi-Layer Feed Forward (MLFF) Artificial Neural Networks (ANNs) are designed for prediction of FGB\'s Cracks\' location and depth. Particle Swarm Optimization (PSO) and Back-Error Propagation (BEP) algorithms are applied for training ANNs. The accuracy of two training methods\' results are investigated.

Key Words
multiple cracks; functionally graded beam; artificial neural network; particle swarm optimization; identification

Address
Mohammad Hossein Abolbashari, Foad Nazari : Department of Mechanical Engineering, Lean Production Engineering Research Center, Ferdowsi University of Mashhad, PO Box 91775-1111, Mashhad, Iran
Javad Soltani Rad : Mechanical Engineering Department, Amirkabir University of Technology, Po Box 15875-4413, Tehran, Iran

Abstract
The present study investigated the effect of the correlation of the measured road roughness profiles corresponding to the left and right wheels of a vehicle on the vibration of a vehicle-bridge coupling system. Four sets of road roughness profiles were measured by a laser road-testing vehicle. A correlation analysis was carried out on the four roughness samples, and two samples with the strongest correlation and weakest correlation were selected for the power spectral density, autocorrelation and cross-correlation analyses. The scenario of a three-axle truck moving across a rigid-frame arch bridge was used as an example. The two selected road roughness profiles were used as inputs to the vehicle-bridge coupling system. Three different input modes were adopted in the numerical analysis: (1) using the measured road roughness profile of the left wheel for the input of both wheels in the numerical simulation; (2) using the measured road roughness profile of the right wheel for both wheels; and (3) using the measured road roughness profiles corresponding to left and right wheels for the input corresponding to the vehicle‟s left and right wheels, respectively. The influence of the three input modes on the vibration of the vehicle-bridge system was analyzed and compared in detail. The results show that the correlation of the road roughness profiles corresponding to left and right wheels and the selected roughness input mode both have a significant influence on the vibration of the vehicle-bridge coupling system.

Key Words
vehicle-bridge coupling system; measured road surface roughness; correlation analysis; autocorrelation; roughness input modes

Address
Wanshui Han : Department of Bridge Engineering, Chang\'an University, Xi\'an 710064, China
Sujing Yuan : School of Civil Engineering, Southeast University, Nanjing 210096, China
Lin Ma : Department of Civil Engineering, Hohai University, Nan\'jing 210098, China

Abstract
Nonlinear bending of super-elliptical plates of uniform thickness under uniform transverse pressure was investigated by the Ritz method. The material was assumed to be homogeneous and isotropic. The contribution of the boundary conditions at the point supports was introduced by the Lagrange multipliers. The solution was obtained by the Newton-Raphson method. The influence of the location of the point supports on the central deflection was highlighted by sensitivity analysis. An approximate relationship between the central deflection and the super-elliptical power was obtained using the method of least squares. The critical points where the maximum deflection may develop, and the influence of nonlinearity were highlighted. The nonlinearity was found to be sensitive to the aspect ratio. The accuracy of the algorithm was validated by comparing the central deflection with the solutions of elliptical and rectangular plates.

Key Words
super-elliptical; plate; nonlinear; bending; large deflection

Address
Murat Altekin : Department of Civil Engineering, Yildiz Technical University, Esenler 34220, Istanbul, Turkey

Abstract
In this study, three approximate analytical methods have been proposed to prepare an accurate analytical solution for nonlinear oscillators with fractional potential. The basic idea of the approaches and their applications to nonlinear discontinuous equations have been completely presented and discussed. Some patterns are also presented to show the accuracy of the methods. Comparisons between Energy Balance Method (EBM) , Variational Iteration Method (VIM) and Hamiltonian Approach (HA) shows that the proposed approaches are very close together and could be easily extend to conservative nonlinear vibrations.

Key Words
natural frequency; nonlinear oscillators; discontinuities; perturbation method

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


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