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CONTENTS
Volume 6, Number 3, September 2017
 

Abstract
A new technique to mitigate irregular buildings with soil structure interaction (SSI) effect subjected to critical seismic waves is presented. The L-shape in plan irregular building for various reasons was selected, subjected to seismic a load which is a big problem for structural design especially without separation gap. The L-shape in plan building with different dimensions was chosen to study, with different rectangularity ratios and various soil kinds, to show the effect of the irregular building on the seismic response. A 3D building subjected to critical earthquake was analyzed by structural analysis program (SAP2000) fixed and with SSI (three types of soils were analyzed, soft, medium and hard soils) to find their effect on top displacement, base shear, and base torsion. The straining actions were appointed and the treatment of the effect of irregular shape under critical earthquake was made by using tuned mass damper (TMD) with different configurations with SSI and without. The study improve the success of using TMDs to mitigate the effect of critical earthquake on irregular building for both cases of study as fixed base and raft foundation (SSI) with different TMDs parameters and configurations. Torsion occurs when the L-shape in plan building subjected to earthquake which may be caused harmful damage. TMDs parameters which give the most effective efficiency in the earthquake duration must be defined, that will mitigate these effects. The parameters of TMDs were studied with structure for different rectangularity ratios and soil types, with different TMD configurations. Nonlinear time history analysis is carried out by SAP2000 with El Centro earthquake wave. The numerical results of the parametric study help in understanding the seismic behavior of L-shape in plan building with TMDs mitigation system.

Key Words
TMD; SSI; building control; irregular buildings; FEM; optimum TMD parameters; non-linear time history analysis

Address
A. A. Farghaly: Civil and Architecture Structures, Sohag University, Sohag, Egypt

Abstract
In this paper, the thermo-mechanical vibration characteristics of functionally graded (FG) nanobeams subjected to three types of thermal loading including uniform, linear and non-linear temperature change are investigated in the framework of third-order shear deformation beam theory which captures both the microstructural and shear deformation effects without the need for any shear correction factors. Material properties of FG nanobeam are assumed to be temperature-dependent and vary gradually along the thickness according to the power-law form. Hence, applying a third-order shear deformation beam theory (TSDBT) with more rigorous kinetics of displacements to anticipate the behaviors of FG nanobeams is more appropriate than using other theories. The small scale effect is taken into consideration based on nonlocal elasticity theory of Eringen. The nonlocal equations of motion are derived through Hamilton\'s principle and they are solved applying analytical solution. The obtained results are compared with those predicted by the nonlocal Euler-Bernoulli beam theory and nonlocal Timoshenko beam theory and it is revealed that the proposed modeling can accurately predict the vibration responses of FG nanobeams. The obtained results are presented for the thermo-mechanical vibration analysis of the FG nanobeams such as the effects of material graduation, nonlocal parameter, mode number, slenderness ratio and thermal loading in detail. The present study is associated to aerospace, mechanical and nuclear engineering structures which are under thermal loads.

Key Words
thermal vibration; functionally graded nanobeam; nonlocal elasticity theory

Address
Farzad Ebrahimi and Mohammad Reza Barati: Mechanical Engineering Department, Faculty of Engineering, Imam Khomeini International University, P.O.B. 16818-34149, Qazvin, Iran

Abstract
We present a simple and easy-to-implement lumped stiffness model to elucidate the load transfer mechanism among all individual tube shells and intertube van der Waals (vdW) interactions in transversely compressed multi-walled carbon nanotubes (CNTs). Our model essentially enables theoretical predictions to be made of the relevant transverse mechanical behaviors of multi-walled tubes based on the transverse stiffness properties of single-walled tubes. We demonstrate the validity and accuracy of our model and theoretical predictions through a quantitative study of the transverse deformability of double- and triple-walled CNTs by utilizing our recently reported nanomechanical measurement data. Using the lumped stiffness model, we further evaluate the contribution of each individual tube shell and intertube vdW interaction to the strain energy absorption in the whole tube. Our results show that the innermost tube shell absorbs more strain energy than any other individual tube shells and intertube vdW interactions. Nanotubes of smaller number of walls and outer diameters are found to possess higher strain energy absorption capacities on both a per-volume and a per-weight basis. The proposed model and findings on the load transfer and the energy absorption in multi-walled CNTs directly contribute to a better understanding of their structural and mechanical properties and applications, and are also useful to study the transverse mechanical properties of other one-dimensional tubular nanostructures (e.g., boron nitride nanotubes).

Key Words
carbon nanotubes; transverse stiffness; load transfer; energy absorption

Address
Xiaoming Chen: Department of Mechanical Engineering, State University of New York at Binghamton, Binghamton, New York 13902, U.S.A.
Changhong Ke:
1) Department of Mechanical Engineering, State University of New York at Binghamton, Binghamton, New York 13902, U.S.A.
2) Materials Science and Engineering Program, State University of New York at Binghamton, Binghamton, New York 13902, U.S.A.

Abstract
This paper studies the particularities of the forced vibration of the hydro-elastic system consisting of a moving elastic plate, compressible viscous fluid and rigid wall. This study is made by employing the discrete-analytical solution method proposed in the paper by the authors (Akbarov and Panakhli (2015)). It is assumed that in the initial state the fluid flow is caused by the axial movement of the plate and the additional lineally-located time-harmonic forces act on the plate and these forces cause additional flow field in the fluid and a stress-strain state in the plate. The stress-strain state in the plate is described by utilizing the exact equations and relations of the linear elastodynamics. However, the additional fluid flow field is described with linearized Navier-Stokes equations for a compressible viscous fluid. Numerical results related to the influence of the problem parameters on the frequency response of the normal stress acting on the plate fluid interface plane and fluid flow velocity on this plane are presented and discussed. In this discussion, attention is focused on the influence of the initial plate axial moving velocity on these responses. At the same, it is established that as a result of the plate moving a resonance type of phenomenon can take place under forced vibration of the system. Moreover, numerical results regarding the influence of the fluid compressibility on these responses are also presented and discussed.

Key Words
compressible viscous fluid; elastic plate; frequency response; critical frequency; moving plate; forced vibration

Address
Surkay D. Akbarov:
1) Yildiz Technical University, Faculty of Mechanical Engineering, Department of Mechanical Engineering, Yildiz Campus, 34349, Besiktas, Istanbul, Turkey
2) Institute of Mathematics and Mechanics of the National Academy of Sciences of Azerbaijan, 37041, Baku, Azerbaijan
Panakh G. Panakhli: Azerbaijan Architecture and Civil Engineering University, Faculty of Mechanical and Information Technologies, Department of Computer Hardware and Software, Baku, Azerbaijan

Abstract
The present paper is concerned with the investigation of Rayleigh waves in a homogeneous transversely isotropic magnetothermoelastic medium with two temperature, in the presence of Hall current and rotation. The formulation is applied to the thermoelasticity theories developed by Green-Naghdi theories of Type-II and Type-III. Secular equations are derived mathematically at the stress free and thermally insulated boundaries. The values of Determinant of secular equations, phase velocity and Attenuation coefficient with respect to wave number are computed numerically. Cobalt material has been chosen for transversely isotropic medium and magnesium material is chosen for isotropic solid. The effects of rotation, magnetic field and phase velocity on the resulting quantities and on particular case of isotropic solid are depicted graphically. Some special cases are also deduced from the present investigation.

Key Words
transversely isotropic thermoelastic; phase velocity; attenuation coefficient; rotation; hall current; secular equations

Address
Rajneesh Kumar: Department of Mathematics, Kurukshetra University, Kurukshetra, Haryana, India
Nidhi Sharma: Department of Mathematics, MM University, Mullana, Ambala, Haryana, India
Parveen Lata: Department of Basic and Applied Sciences, Punjabi University, Patiala, Punjab, India
S. M. Abo-Dahab: Department of Mathematics, Faculty of Science, South Valley University, Qena 83523, Egypt

Abstract
To cope with the demand on giant and durable buildings, reinforcement of concrete is a practical problem being extensively investigated in the civil engineering field. Among various reinforcing techniques, fiber-reinforced concrete (FRC) has been proven to be an effective approach. In practice, such fibers include steel fibers, polyvinyl alcohol (PVA) fibers, polyacrylonitrile (PAN) carbon fibers and asbestos fibers, with the length scale ranging from centimeters to micrometers. When advancing such technique down to the nanoscale, it is noticed that carbon nanotubes (CNTs) are stronger than other fibers and can provide a better reinforcement to concrete. In the last decade, CNT-reinforced concrete attracts a lot of attentions in research. Despite high cost of CNTs at present, the growing availability of carbon materials might push the usage of CNTs into practice in the near future, making the reinforcement technique of great potential. A review of existing research works may constitute a conclusive reference and facilitate further developments. In reference to the recent experimental works, this paper reports some key evaluations on CNT-reinforced cementitious materials, covering FRC mechanism, CNT dispersion, CNT-cement structures, mechanical properties and fire safety. Emphasis is placed on the interplay between CNTs and calcium silicate hydrate (C-S-H) at the nanoscale. The relationship between the CNTs-cement structures and the mechanical enhancement, especially at a high-temperature condition, is discussed based on molecular dynamics simulations. After concluding remarks, challenges to improve the CNTs reinforcement technique are proposed.

Key Words
carbon nanotube (CNT); fiber-reinforced concrete (FRC); mechanical properties; fire safety

Address
Zechuan Yu: Department of Architecture and Civil Engineering, City University of Hong Kong, Hong Kong, China
Denvid Lau:
1) Department of Architecture and Civil Engineering, City University of Hong Kong, Hong Kong, China
2) Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, U.S.A.

Abstract
In this article, the multiphysics response of magneto-electro-elastic (MEE) cantilever beam subjected to thermo-mechanical loading is analysed. The equilibrium equations of the system are obtained with the aid of the principle of total potential energy. The constitutive equations of a MEE material accounting the thermal fields are used for analysis. The corresponding finite element (FE) formulation is derived and model of the beam is generated using an eight noded 3D brick element. The 3D FE formulation developed enables the representation of governing equations in all three axes, achieving accurate results. Also, geometric, constitutive and loading assumptions required to dimensionality reduction can be avoided. Numerical evaluation is performed on the basis of the derived formulation and the influence of various mechanical loading profiles and volume fractions on the direct quantities and stresses is evaluated. In addition, an attempt has been made to compare the individual effect of thermal and mechanical loading with the combined effect. It is believed that the numerical results obtained helps in accurate design and development of sensors and actuators.

Key Words
finite element; magneto-electro-elastic beam; thermo-mechanical load; direct quantities; volume fraction

Address
Vinyas M. and S.C. Kattimani: Department of Mechanical Engineering, National Institute of Technology Karnataka, Surathkal, 575025, India

Abstract
Intermolecular interaction energies and conformer geometries of the hydrogen bonded acrylamide dimers have been studied by using the second-order Moller-Plesset (MP2) perturbation theory and the density functional theory (DFT) with 17 density functionals. Dunning\'s correlation consistent basis sets (up to aug-cc-pVTZ) have been used to study the basis set effects. The DFT calculated interaction energies are compared to the reference energy data calculated by the MP2 method and the coupled cluster method at the complete basis set (CCSD(T)/CBS) limit in order to determine the relative performance of the studied density functionals. Overall, dispersion-energy-corrected density functionals outperform uncorrected ones. The wB97XD density functional is particularly effective in terms of both accuracy and computational cost in estimating the reference energy values using small basis sets and is highly recommended for similar calculations for larger systems.

Key Words
acrylamide dimer; ab initio calculation; density functional theory; hydrogen bonded complexes

Address
Yi-De Lin, Yi-Siang Wang and Sheng D. Chao: Institute of Applied Mechanics, National Taiwan University, Taipei 106, Taiwan, R.O.C.


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