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CONTENTS
Volume 80, Number 3, November10 2021
 


Abstract
Ultrasonic nondestructive testing with guided waves is applied for the detection of defects in thin plates. The most important advantage of the application of guided waves is the efficient inspection of structures, such as thin plates and pipes. However, owing to the wave dispersion and wave mode excitability in plates, the wave propagation inside them becomes more complex. Thus, in this study, we developed defect detection for thin plate inspection using guided waves by using the time reversal method, which takes advantage of the reciprocity and reversibility characteristics of waves. However, it is difficult to determine the convergence point of time reversal waves, whose point corresponds to the location of the defect. In this study, the topological sensitivity is utilized as the indicator of defect detection for the time reversal method. In this paper, we first explain the problem to be solved for a scattering problem of 2-D SH guided waves. Next, the forward analysis method for demonstrating scattered wave fields is discussed. Afterwards, a brief description of the time reversal method and the topological sensitivity is introduced. Finally, the topological sensitivity obtained from the forward and time reversal analysis results is calculated to detect surface cracks in thin plates.

Key Words
finite element method; guided wave; SH wave; time reversal method; topological sensitivity

Address
Takahiro Saitoh:Department of Civil and Environmental Engineering, Gunma University, 1-5-1, Tenjin, Kiryu, Gunma, Japan
Asumi Ishiguro: Environmental Engineering Science Course, Gunma University, 1-5-1, Tenjin, Kiryu, Gunma, Japan

Abstract
In this study, the cylindrical shell submerged in a fluid and surrounded by ring supports. The use of acoustic wave equation is done to incorporate the sound pressure produced in a fluid. Hankel's functions of second kind designate the fluid influence. Mathematically the integral form of the Lagrange energy functional is converted into a set of three partial differential equations. Shell motion equations are framed first order shell theory due to Love. These equations are partial differential equations which are usually solved by approximate technique. The transverse constraints produced ring supports are assumed by the polynomial functions possessing degree equal to the number of ring supports. The frequencies with ring supports against wave number, length-to-radius ratio and height-to-radius ratio are investigated. The frequency analysis versus wave number for simply supported cylindrical shells submerged in a fluid with ring supports is given for different types of configuration. The variations of frequencies against the positions of the ring supports are furnished for not submerged and submerged cylindrical shells. It is observed that vibration frequencies increase and decreases as the positions of a ring support is increased. Programming is written in MATLAB codes to solve the frequency equation for the computation of frequencies of shells submerged in a fluid along with ring supports. The frequency result of submerged cylindrical shell is less than with the results of not submerged cylindrical shell. Robust and efficient technique produced the valid results.

Key Words
Hankel's functions shell; MATLAB; ring supports; wave equation

Address
Mohamed A. Khadimallah: Civil Engineering Department, College of Engineering, Prince Sattam Bin Abdulaziz University, Al-Kharj, 16273, Saudi Arabia; Laboratory of Systems and Applied Mechanics, Polytechnic School of Tunisia, University of Carthage, Tunis
Muzamal Hussain: Department of Mathematics, Govt. College University Faisalabad, 38000, Faisalabad, Pakistan
Ahmad Yahya: Nuclear Engineering Department, King Abdulaziz University, Jeddah, Saudi Arabia
Khaled Mohamed Khedher: Department of Civil Engineering, College of Engineering, King Khalid University, Abha 61421, Saudi Arabia; Department of Civil Engineering, High Institute of Technological Studies, Mrezgua University Campus, Nabeul 8000, Tunisia
Faisal Al-Thobiani: Marine Engineering Department, Faculty of Maritime Studie, King Abdulaziz University, Jeddah, Saudi Arabia
Shauket Ali Tahir: Department of Mathematics and Statistics, The University of Lahore, Lahore, 54000, Pakistan
Abdelouahed Tounsi: YFL (Yonsei Frontier Lab), Yonsei University, Seoul, Korea; Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia

Abstract
The present article deals with the propagation of Rayleigh surface waves in homogeneous orthotropic medium. This thermoelastic problem is studied under the purview of three-phase-lag model of hyperbolic thermoelasticity in the presence of voids. The normal mode analysis is employed to obtain a vector matrix differential equation which is then solved by eigenvalue approach. The frequency equations for different cases are derived. In order to illustrate the analytical developments, the numerical solution is carried out and the computer simulated results in respect of phase velocity and attenuation coefficient are presented graphically. Phase velocity and attenuation coefficient decreases in the presence of voids. The present problem is the most general one as other problems can be obtained as special cases from it.

Key Words
eigenvalue approach; orthotropic medium; Rayleigh wave; three-phase-lag model; voids

Address
Siddhartha Biswas: Department of Mathematics, University of North Bengal, Darjeeling, India

Abstract
Nonlinear free vibration and thermal buckling of a beam resting on nonlinear are investigated in this study. In the nonlinear kinematic relations, the finite strain theory is used with Euler-Bernoulli and Hamilton's principle is employed to derive the nonlinear governing of motion. The Galerkin's method is applied to simplify the governing nonlinear partially differential equation to the nonlinear ordinary differential equation. In addition, He's variational method is employed to obtain an analytical expression for the nonlinear natural frequency and thermal buckling temperature. In this study, a comparison between the finite strain theory and the von Kármán Theory is presented and the results shows that the finite strain theory gives more accurate results than the von Kármán Theory for nonlinear natural frequency and thermal buckling temperature. In the numerical results, the effect of different parameters such as linear and nonlinear coefficients of the elastic foundation, boundary conditions and the amplitude of the oscillation on the thermal buckling temperature and the nonlinear natural frequency investigated.

Key Words
finite strain theory; He's variational method; nonlinear thermal buckling; nonlinear vibration

Address
M. Alimoradzadeh: Department of Mechanical Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran
Ş.D. Akbaş: Department of Civil Engineering, Bursa Technical University, 16330, Bursa, Turkey
S.M. Esfrajani: Department of Mechanical Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran

Abstract
A method to minimize the economic cost of the structural design of spatial reinforced concrete (RC) frame structures is presented. SAP2000 is used as computational engine, taking into account modelling aspects such as static soilstructure interaction (SSSI). The optimization problem is formulated to properly reflect an actual design problem, limiting e.g., the size of reinforcement bars to commercially available sections. The resulting discrete optimization problem is solved by using Biogeography-Based Optimization (BBO), an evolutionary algorithm selected for its convergence properties. Strategies to reduce the computational cost of the optimization procedure are proposed and an extensive tuning of the parameters of the BBO algorithm is performed, using a novel utility metric, evaluated for models of six simple RC frame structures. The parameters to deal with more complex structures are selected based on the use of utility landscapes. The resulting tuned optimization algorithm allows to reduce the direct cost of the construction of a particular structure project with 21% (15% when SSSI is not taken into account), compared to a design based on traditional criteria. The effect of considering SSSI on the cost of the superstructure is also evaluated, showing that this is an aspect that should not be neglected during modeling.

Key Words
Biogeography-Based Optimization; evolutionary algorithm; parameter tuning; reinforcement concrete structures; static soil-structure interaction; structural optimization

Address
Iván A. Negrin: Department of Civil Engineering, Faculty of Construction, Marta Abreu Central University, Santa Clara, Cuba
Dirk Roose: Department of Computer Science, KU Leuven, Belgium
Ernesto L. Chagoyén: Department of Civil Engineering, Faculty of Construction, Marta Abreu Central University, Santa Clara, Cuba
Geert Lombaert: Department of Civil Engineering, KU Leuven, Belgium

Abstract
In order to ensure the safety of glass fiber reinforced polymer (GFRP)-concrete composite bridge deck, its static and fatigue behaviors were studied by both experimental and numerical method in this paper. First, static and fatigue loading tests were carried out to investigate the mechanical properties of the GFRP-concrete composite slab. The experimental results indicated that the composite bridge deck had a good fatigue resistance. Then, a finite element model was built and the accuracy of the model was verified by comparing the simulated results with the static experiment. Third, corresponding constitutive models and failure criterions were introduced to simulate the fatigue performance of GFRP-concrete composite slab by using both finite element method and theoretical layered method. Generally, the calculated values were in good agreement with the test values, and the proposed method can be used to predict the deflection and strain of the components. Finally, parametric analysis was conducted to investigate the stiffness degradation of the composite structure.

Key Words
fatigue simulation; finite element analysis; GFRP-concrete composite deck; model test; theoretical method

Address
Xiaodong Song, Yili Huang, Qiao Huang: Department of Bridge Engineering, School of Transportation, Southeast University, Nanjing, China
Huakai Zheng: Department of Bridge Engineering, School of Transportation, Southeast University, Nanjing, China; Jiangsu Provincial Traffic Engineering Construction Bureau, China

Abstract
Recently, modular prefabricated steel moment connections have been widely studied by several researchers. These connections are made of tubular columns that are ended to horizontal plates at both sides, an inter-story short column, and truss beams that are joined to the connecting plates using top and bottom plates. In this study, a series of equations have been developed and presented for designing each component of this type of connection. Then, to verify the proposed equations, the connection was modeled in ABAQUS and then the results extracted from the equations and modeling were compared. The findings indicated that the proposed equations have the required accuracy.

Key Words
ABAQUS; design equations; finite element method; prefabricated steel moment connection

Address
Seyed Morteza Kazemi: Department of Civil Engineering, Kashmar Branch, Islamic Azad University, Kashmar, Iran
Mohammad Reza Sohrabi: Civil Engineering Department, University of Sistan and Baluchestan, Zahedan, Iran
Hasan Haji Kazemi: Civil Engineering Department, Ferdowsi University, Mashhad, Iran

Abstract
The present study pertains to the in-plane bending deflections of reinforced concrete beams with multiple regular transverse openings along the beam length. The total deflections in the beam were obtained from bending deflections and the additional deflections from the Vierendeel panel action. The accuracy of the deflection estimates from the proposed formula were observed to depend on the opening geometry. Among different geometries, the presence of rectangular and parallelogram web openings resulted in the experimental deflections to deviate more considerably from the analytical values due to the stress concentrations around the corners of the openings. Consequently, a multiplier was incorporated into the deflection formula to account for the opening geometry. The new revised formula was found to generate analytical load-deflection curves in close agreement with the experimental ones and service-load deflections close to the FEA values of beams with varying amount of tension reinforcement. The diagonal reinforcement around the openings and the short stirrups in the posts and chords increased the accuracy of the analytical deflection estimates by reducing the undesired additional deformations in the beam due to the poorer integrity of the posts and chords around the openings.

Key Words
chord; effective moment of inertia; post; vierendeel failure; web opening

Address
Ilker Kalkan: Department of Civil Engineering, Faculty of Engineering and Architecture, Kirikkale University, 71450 Kirikkale, Turkey
Ece Ceylan: Ministry of Health, 06800 Cankaya, Ankara, Turkey
Saruhan Kartal: Department of Civil Engineering, Faculty of Engineering and Architecture, Kirikkale University, 71450 Kirikkale, Turkey
Mehmet Baran: Department of Civil Engineering, Faculty of Engineering and Natural Sciences, Ankara Y

Abstract
Owing to the increase in demand for composite materials for different applications in aircraft structures, the nonlinear response of functionally graded ceramic-metal sandwich plates under mechanical loading is studied in the present research work. Geometric nonlinearity (GNL) is considered by Green-strain components and further assumes the form of von Kármán strains. It is ascertained that the effective mechanical properties vary through the thickness direction as a function of volume fraction of ceramic and metal constituents and obeys power law equation. Higher order displacement model proposed by Reddy is incorporated in the study to arrive for 2D isoparametric finite element C0 formulation. A nine node Lagrangian element is accomplished to model the assumed plate geometry. Different thickness schemes are proposed to model the sandwich plate with graded layer as core/ face sheets. Although the model can handle thickness scheme of any kind, results are exposed for four types of symmetric sandwich plates. Comparison statement between isotropic and graded plates is drawn in each case by appropriate selection of power law exponent value. The present investigation may be useful for design engineers/researchers to arrive for particular thickness scheme based on the results, while performing large deformation analysis of functionally graded sandwich plates (FGSP).

Key Words
finite element method; functionally graded materials; mechanics of materials; nonlinear analysis; sandwich plates; von Kármán strains

Address
M.N.A. GulshanTaj, R. Malathy, S.R.R. Senthil Kumar: Department of Civil Engineering, Sona College of Technology, Salem- 636005, India
Anupam Chakrabarti: Department of Civil Engineering, Indian Institute of Technology Roorkee, Roorkee- 247667, India

Abstract
Steel hollow section (SHS) columns have been increasingly popular in structural systems due to high compressive capacity, excellent torsional strength, and symmetric bending stiffness. In moment-resisting frames, the structural performance of connections to SHS columns is important to ensure the ability to carry bending moment. Conventional connections utilize welds to connect the adjacent components to the columns. Brittle fracture often initiates at the welds and reduces the ductility of connections. In this research, bolted connections were proposed to connect the beam to the SHS column through through-diaphragm. Tensile tests were conducted on four specimens to evaluate the structural behavior of connections. Failure mode, load-displacement response, strength, stiffness, and ductility were analyzed. The test results showed that the specimens were failed by the necking down of the flange plate. All specimens had high load-carrying capacity and good ductility. Strain distributions at key locations were investigated to study the force flow path. The application of through-diaphragm was found to deliver the tensile load to larger area and thus reduced the stress concentration at the connecting zone. Moreover, large amount of stress was transferred directly through the diaphragm, and the required stress demand for the SHS column was decreased. Design method was then proposed to predict the yield and the ultimate strength of the bolted connections. Good agreement was found between the experimental results and the theoretical predictions.

Key Words
bolted; design method; SHS column; tensile behavior; through-diaphragm

Address
Ying Qin: Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, School of Civil Engineering, Southeast University, Nanjing, China;
State Key Laboratory of Green Building in Western China, Xi'an University of Architecture & Technology, Xi'an, China;
Key Laboratory of Civil Engineering Structure and Mechanics, Inner Mongolia University of Technology, Hohhot, China
Jingchen Zhang, Yifu Chen, Peng Shi, Yaohan Xu, Zuozheng Shi: Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, School of Civil Engineering, Southeast University, Nanjing, China


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