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CONTENTS
Volume 44, Number 4, August25 2022
 


Abstract
In the present paper, the static bending and buckling responses of functionally graded carbon nanotubes-reinforced composite (FG-CNTRC) beam under various boundary conditions are investigated within the framework of higher shear deformation theory. The significant feature of the proposed theory is that it provides an accurate parabolic distribution of transverse shear stress through the thickness satisfying the traction-free boundary conditions needless of any shear correction factor. Uniform (UD) and four graded distributions of CNTs which are FG-O, FG-X, FG- and FG-V are selected here for the analysis. The effective material properties of FG-CNTRC beams are estimated according to the rule of mixture. To model the FG-CNTRC beam realistically, an efficient Hermite–Lagrangian finite element formulation is successfully developed. The accuracy and efficiency of the present model are demonstrated by comparison with published benchmark results. Moreover, comprehensive numerical results are presented and discussed in detail to investigate the effects of CNTs volume fraction, distribution patterns of CNTs, boundary conditions, and length-to-thickness ratio on the bending and buckling responses of FGCNTRC beam. Several new referential results are also reported for the first time which will serve as a benchmark for future studies in a similar direction. It is concluded that the FG-X-CNTRC beam is the strongest beam that carries the lowest central deflection and is followed by the UD, V, Λ, and FG-O-CNTRC beam. Besides, the critical buckling load belonging to the FG-XCNTRC beam is the highest, followed by UD and FG-O.

Key Words
bending; buckling; carbon nanotubes; finite elements; functionally graded material

Address
Mohamed-Ouejdi Belarbi:Laboratoire de Recherche en Genie Civil, LRGC, Universite de Biskra, B.P. 145, R.P. 07000, Biskra, Algeria

Sattar Jedari Salami:Department of Biomedical Engineering, Central Tehran branch, Islamic Azad University, Tehran, Iran

Aman Garg:Department of Civil and Environmental Engineering, The NorthCap University, Gurugram, Haryana, India

Hicham Hirane:Laboratoire de Recherche en Genie Civil, LRGC, Université de Biskra, B.P. 145, R.P. 07000, Biskra, Algeria

Daikh Ahmed Amine:Department of Technology, University Centre of Naama, 45000 Naama, P.O.Box 66, Algeria

Mohammed Sid Ahmed Houari:Laboratoire d'Etude des Structures et de Mecanique des Materiaux, Departement de Genie Civil, Faculte des Sciences et de la Technologie,
Universite Mustapha Stambouli B.P. 305, R.P. 29000 Mascara, Algerie

Abstract
A high-speed railway (HSR) bridge may undergo long-term deformation due to the degradation of material stiffness, or foundation settlement during its service cycle. In this study, an analytical model is set up to evaluate the influence of this longterm vertical bridge deformation on the track geometry. By analyzing the structural characteristics of the HSR track-bridge system, the energy variational principle is applied to build the energy functionals for major components of the track-bridge system. By further taking into account the interlayer's force balancing requirements, the mapping relationship between the deformation of the track and the one of the bridge is established. In order to consider the different behaviors of the interlayers in compression and tension, an iterative method is introduced to update the mapping relationship. As for the validation of the proposed mapping model, a finite element model is created to compare the numerical results with the analytical results, which show a good agreement. Thereafter, the effects of the interlayer's different properties of tension and compression on the mapping deformations are further evaluated and discussed.

Key Words
energy variational principle; high-speed railway; longitudinal continuous track; track geometry; track/bridge interaction

Address
Zhipeng Lai:1)School of Civil Engineering, Central South University, Changsha 410075, China
2)National Engineering Center for High-speed Railway Construction, Changsha 410075, China

Lizhong Jiang:1)School of Civil Engineering, Central South University, Changsha 410075, China
2)National Engineering Center for High-speed Railway Construction, Changsha 410075, China

Xiang Liu:School of Civil Engineering, Central South University, Changsha 410075, China

Yuntai Zhang:School of Civil Engineering, Central South University, Changsha 410075, China

Tuo Zhou:School of Civil Engineering, Central South University, Changsha 410075, China

Abstract
The stiffeners, also known as ribs, are utilized to increase the resistance of T-stubs. The author's previous studies showed that stiffeners can increase plastic capacity by an average of 1.71 times. A combined experimental and numerical study was undertaken to examine the effects of the stiffener configuration on the behavior of T-stubs. A total of 20 stiffened T-stubs where the shape and angle of stiffeners were considered as the main parameters were tested under monotonic loading. Rectangular, triangular and AISC types of stiffener were tested under monotonic loading. The experimental results indicated that when the height of the stiffener is equal to or higher than the length of the stiffener, the shape of the stiffener does not have an influence on the behavior. A numerical study using the finite element tool ABAQUS was carried out in order to further investigate the effects of the stiffener shapes. In this case, the height is considered less than the length of the stiffener. Moreover, the shape of the stiffeners was investigated with the different thicknesses of the stiffener. The simulation findings revealed that when the height of the stiffener is less than the length of the stiffener, the shape of the stiffener significantly affects the plastic capacity. Based on the numerical and experimental results, it is recommended to use the triangular shape of the stiffener when height is equal to or higher than the length of the stiffener while it is recommended to utilize the rectangular shape of the stiffener when height is less than the length of the stiffener.

Key Words
angle; experimental; numerical; stiffener; shape; T-stub; thickness

Address
Yasin Onuralp Ozkic:Department of Civil Engineering, Necmettin Erbakan University, 42100, Konya, Turkey

Abstract
This paper presents the mechanical buckling of bi-directional functionally graded sandwich beams (BFGSW) with various boundary conditions employing a quasi-3D beam theory, including an integral term in the displacement field, which reduces the number of unknowns and governing equations. The beams are composed of three layers. The core is made from two constituents and varies across the thickness; however, the covering layers of the beams are made of bidirectional functionally graded material (BFGSW) and vary smoothly along the beam length and thickness directions. The power gradation model is considered to estimate the variation of material properties. The used formulation reflects the transverse shear effect and uses only three variables without including the correction factor used in the first shear deformation theory (FSDT) proposed by Timoshenko. The principle of virtual forces is used to obtain stability equations. Moreover, the impacts of the control of the power-law index, layer thickness ratio, length-to-depth ratio, and boundary conditions on buckling response are demonstrated. Our contribution in the present work is applying an analytical solution to investigate the stability behavior of bidirectional FG sandwich beams under various boundary conditions.

Key Words
deformation demand; earthquake resistant design philosophy; limit states; structural damage states; levels of earthquake shaking

Address
Abdelhak Berkia:1)Laboratory of Materials and Reactive Systems, Department of mechanical Engineering, University of Sidi Bel Abbes, Faculty of Technology,
Algeria 2)Department of mechanical Engineering, University of Abbés Laghrour Khenchela, Faculty of Science and Technology, Algeria

Soumia Benguediab:1)Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria
2) Universite Dr Tahar Moulay, Faculte de Technologie, Departement de Genie Civil et Hydraulique, BP 138 Cite En-Nasr 20000 Saida, Algerie

Abderrahmane Menasria:1)Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria 2)Department of Civil Engineering, University of Abbes Laghrour Khenchela, Faculty of Science and Technology, Algeria

Abdelhakim Bouhadra:1)Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria 2)Department of Civil Engineering, University of Abbes Laghrour Khenchela, Faculty of Science and Technology, Algeria

Fouad Bourad:1)Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria 2)Departement des Sciences et de la Technologie, universite de Tissemsilt, BP 38004 Ben Hamouda, Algeria

Belgacem Mamen:1)Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria 2)Department of Civil Engineering, University of Abbes Laghrour Khenchela, Faculty of Science and Technology, Algeria

Abdelouahed Tounsi:1)Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria 2)YFL (Yonsei Frontier Lab), Yonsei University, Seoul, Korea 3)Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals,31261 Dhahran, Eastern Province, Saudi Arabia
4)Interdisciplinary Research Center for Construction and Building Materials, KFUPM, Dhahran, Saudi Arabia
10Department of Mathematics, Govt. College University Faisalabad, 38000, Faisalabad, Pakistan

Kouider Halim Benrahou:Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria

Mohamed Benguediab:Laboratory of Materials and Reactive Systems, Department of mechanical Engineering, University of Sidi Bel Abbes, Faculty of Technology,
Algeria

Muzamal Hussain:Department of Mathematics, Govt. College University Faisalabad, 38000, Faisalabad, Pakistan


Abstract
Sandwich structures with the superior mechanical properties such as high stiffness and strength-to-weight ratio, good thermal insulation, and high energy absorption capacity are used today in aerospace, automotive, marine, and civil engineering industries. These structures are composed of moderately stiff, thin face sheets that withstand the majority of transverse and in-plane loads, separated by a thick, lightweight core that resists shear forces. In this research, the finite element technique is used to simulate a sandwich panel with a truss core under axial compressive stress using ABAQUS software. A review of past experimental studies shows that the bondline between the core and face sheets plays a vital role in the critical failure load. Therefore, this modeling analyzes the damage initiation modes and debonding between face sheet and core by cohesive surface contact with traction-separation model. According to the results obtained from the modeling, it can be observed that the adhesive stiffness has a significant influence on the critical failure load of the specimens. To achieve the full strength of the structure as a continuum, a lower limit is obtained for the adhesive stiffness. By providing this limit stiffness between the core and the panel face sheets, sudden failure of the structure can be prevented.

Key Words
cohesive surface contact; face/core debonding; in-plane compression; sandwich panel; truss cor

Address
Mohammad J. Zarei, Shahabeddin Hatami and Mohammad Gholami:Faculty of Engineering, Yasouj University, Iran

Abstract
An exact dynamic analytical method for free vibrations of continuous partial-interaction composite beams is proposed based on the Timoshenko beam theory. The main advantage of this method is that the independent shear deformations and rotary inertia of sub-beams are considered, which is more in line with the reality. Therefore, the accuracy of eigenfrequencies obtained by this method is significantly improved, especially for higher order modes, compared to the existing methods where the rotary angles of both sub-beams are assumed to be equal irrespective of the differences in the shear stiffness of each sub-beam. Furthermore, the solutions obtained by the proposed method are exact owing to no introduction of approximated displacement and force fields in the derivation. In addition, an exact analytical solution for the case of simply supported is obtained. Based on this, an approximate expression for the fundamental frequency of continuous partial-interaction composite beams is also proposed, which is useful for practical engineering applications. Finally, the practicability and effectiveness of the proposed method and the approximate expression are explored using numerical and experimental examples; The influence factors including the interfacial interaction, shear modulus ratio, span-to-depth ratio, and side-to-main span length ratio on the eigenfrequencies are presented and discussed in detail.

Key Words
approximate expression; continuous partial-interaction composite beam; exact dynamic analytical method; free vibrations; influence factors

Address
Kai Q. Sun:School of Civil Engineering, Beijing Jiaotong University, Beijing 100044, China

Nan Zhang:School of Civil Engineering, Beijing Jiaotong University, Beijing 100044, China

Qun X. Zhu:School of Civil and Environmental Engineering, University of Technology Sydney (UTS), Sydney NSW 2007, Australia

Xiao Liu:School of Civil Engineering, Beijing Jiaotong University, Beijing 100044, China


Abstract
Empirical relationships that capture the nonlinear behavior of headed steel shear stud anchors have been derived from standard push out tests, where the specimens are comprised of large wide flanged steel sections attached to flat concrete slabs via the anchors. However, many composite systems used in practice utilize much smaller steel members and/or steel decking as part of the slab system. Composite open web steel joist systems generally include both of these elements and consequently the nonlinear performance ofthe anchor is not accurately represented by existing models. In this paper, a new empirical relation is presented for open web steel joist systems based on experimental results from a modified push out test that more realistically represent a composite open web steel joist system. The methodology for obtaining the proposed nonlinear function where the response of the system is characterized by two parameters(α and β) is presented. The two-step process for obtaining the two parameters is described and the empirical relation is calibrated with the experimental data. In comparison with existing expressions, the new proposal herein more accurately predicts the high initialstiffness of the system and overall nonlinear system performance.

Key Words
composite open web steel joist system; headed shear stud anchor; nonlinear behavior; push-out test; Savitzki-Golay filter

Address
Sergio J. Yanez:University of Santiago of Chile (USACH), Faculty of Engineering, Civil Engineering Department, Chile

David W. Dinehart:Villanova University, Department of Civil and Environmental Engineering, USA

Juan Carlos Pina:University of Santiago of Chile (USACH), Faculty of Engineering, Civil Engineering Department, Chile

Carlos Felipe Guzman:University of Santiago of Chile (USACH), Faculty of Engineering, Civil Engineering Department, Chile

Abstract
Nonlinear free vibration analysis of a functionally graded beam resting on the nonlinear viscoelastic foundation is studied with uniform temperature rising. The non-linear strain-displacement relationship is considered in the finite strain theory. The governing nonlinear dynamic equation is derived based on the finite strain theory with using of Hamilton's principle. The Galerkin's decomposition technique is utilized to discretize the governing nonlinear partial differential equation to nonlinear ordinary differential equation and then is solved by using of multiple time scale method. The influences of temperature rising, material distribution parameter, nonlinear viscoelastic foundation parameters on the nonlinear free response and phase trajectory are investigated. In this paper, it is aimed that a contribution to the literature for nonlinear thermal vibration solutions of a functionally graded beam resting on the nonlinear viscoelastic foundation by using of multiple time scale method.

Key Words
functionally graded material; nonlinear vibration; temperature rising; viscoelastic nonlinear foundation

Address
M. Alimoradzadeh:Department of Mechanical Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran

S.D. Akbas:Department of Civil Engineering, Bursa Technical University, 16330, Bursa, Turkey


Abstract
This study introduces a novel friction damper as a component of a recentering frame connection, to solve the problem of structural repair costs, caused by stiffness deterioration and brittle fracture of the central brace frame (CBF). The proposed damper consists of shape memory alloy (SMA) bars with pretension applied to them to improve the stability. SMAs reduce the residual displacement by virtue of the properties of the materials themselves; in addition, a pretension can be applied to partially improve their energy dissipation capacity. The damper also consists of a friction device equipped with friction bolts for increased energy dissipation. Therefore, a study was conducted on the effects of the friction device as well as the pretension forces on the friction damper. For performance verification, 12 cases were studied and analyzed using ABAQUS program. In addition, the friction and pretension forces were used as variables in each case, and the results were compared. As a result, when the pretension and friction force are increased, the energy dissipation capacity gradually increases by up to about 94% and the recentering capacity decreases by up to about 55%. Therefore, it has been shown that SMA bars with adequate pretension in combination with bolts with adequate frictional force effectively reduce residual deformation and increase damper capacity. Thus, this study has successfully proposed a novel friction damper with excellent performance in terms of recentering and energy dissipation capacity.

Key Words
finite element analysis; friction devices; pretensioned SMA bars; recentering; smart damper

Address
Young Chan Kim and Jong Wan Hu:1)Incheon Disaster Prevention Research Center, Incheon National University, Incheon 22012, South Korea
2)Department of Civil and Environmental Engineering, Incheon National University, Incheon 22012, South Korea

Abstract
In this study, the classical J2 flow theory is explicitly proved to be inappropriate to describe the plastic behaviour of structural steels under different stress states according to the reported test results. A numerical framework of the characterization of the strain hardening and ductile fracture initiation involving the effect of stress states, i.e., stress triaxiality and Lode angle parameter, is proposed based on the mechanical response of structural steels under monotonic loading. Both effects on strain hardening are determined by correction functions, which are implemented as different modules in the numerical framework. Thus, other users can easily modify them according to their test results. Besides, the ductile fracture initiation is determined by a fracture locus in the space of stress triaxiality, Lode angle parameter, and fracture strain. The numerical implementation of the proposed model and the corresponding code are provided in this paper, which are also available on GitHub. The validity of the numerical procedure is examined through single element tests and the accuracy of the proposed model is verified by existing test results.

Key Words
ductile fracture; lode angle parameter; strain hardening; stress triaxiality; structure steels

Address
Qun He:1)Department of Building and Real Estate, The Hong Kong Polytechnic University, Hong Kong, China
2)Chinese National Engineering Research Centre for Steel Construction (Hong Kong Branch),
The Hong Kong Polytechnic University, Hong Kong, China

Michael C.H. Yam:1)Department of Building and Real Estate, The Hong Kong Polytechnic University, Hong Kong, China
2)Chinese National Engineering Research Centre for Steel Construction (Hong Kong Branch),
The Hong Kong Polytechnic University, Hong Kong, China

Zhiyang Xie:State Key Laboratory of Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, China

Xue-Mei Lin:1)Department of Building and Real Estate, The Hong Kong Polytechnic University, Hong Kong, China
2)Chinese National Engineering Research Centre for Steel Construction (Hong Kong Branch),
The Hong Kong Polytechnic University, Hong Kong, China

Kwok-Fai Chung:1)Chinese National Engineering Research Centre for Steel Construction (Hong Kong Branch),
The Hong Kong Polytechnic University, Hong Kong, China
2)Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong, China



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