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CONTENTS
Volume 8, Number 4, August 2019
 

Abstract
Reinforced concrete can be considered as a heterogeneous material consisting of coarse aggregate, mortar mix and reinforcing bars. This paper presents a two-dimensional mesoscopic analysis of reinforced concrete beams using a simple two-phase mesoscopic model for concrete. The two phases of concrete, coarse aggregate and mortar mix are bonded together with reinforcement bars so that inter force transfer will occur through the material surfaces. Monte Carlo\'s method is used to generate the random aggregate structure using the constitutive model at mesoscale. The generated models have meshed such that there is no material discontinuity within the elements. The proposed model simulates the load-deflection behavior, crack pattern and ultimate load of reinforced concrete beams reasonably well.

Key Words
mesoscopic analysis; reinforced concrete beam; deep beam; two-phase

Address
Tintu Shine A.L.: Department of Civil Engineering, Viswajyothi College of Engineering and Technology, Ernakulam, India

Fincy Babu: Kerala Rural Water Supply and Sanitation Agency, Kerala, India

Dhileep M.: Department of Civil Engineering, Muthoot Institute of Technology & Science, Ernakulam, India

Abstract
The paper represents computer modeling of the deformed state of physically nonlinear transversally isotropic bodies with hole. In order to describe the anisotropy of the mechanical properties of transversally-isotropic materials a structurally phenomenological model has been used. This model allows representing the initial material in the form of the coupled isotropic materials: the basic material (binder) considered from the positions of continuum mechanics and the fiber material oriented along the anisotropy direction of the original material. It is assumed that the fibers perceive only the axial tensile-compression forces and are deformed together with the base material. To solve the problems of the theory of plasticity, simplified theories of small elastoplastic deformation have been used for a transversely-isotropic body, developed by B.E. Pobedrya. A simplified theory allows applying the theory of small elastoplastic deformations to solve specific applied problems, since in this case the fibrous medium is replaced by an equivalent transversely isotropic medium with effective mechanical parameters. The essence of simplification is that with simple stretching of composite in direction of the transversal isotropy axis and in direction perpendicular to it, plastic deformations do not arise. As a result, the intensity of stresses and deformations both along the principal axis of the transversal isotropy and along the perpendicular plane of isotropy is determined separately. The representation of the fibrous composite in the form of a homogeneous anisotropic material with effective mechanical parameters allows for a sufficiently accurate calculation of stresses and strains. The calculation is carried out under different loading conditions, keeping in mind that both sizes characterizing the fibrous material fiber thickness and the gap between the fibers-are several orders smaller than the radius of the hole. Based on the simplified theory and the finite element method, a computer model of nonlinear deformation of fibrous composites is constructed. For carrying out computational experiments, a specialized software package was developed. The effect of hole configuration on the distribution of deformation and stress fields in the vicinity of concentrators was investigated.

Key Words
FEM; transversally-isotropic medium; computational experiment; fibrous composite; elasticity; plasticity; hole; strain; stress

Address
Askhad M. Polatov and Akhmat M. Ikramov: Department of Mathematics, National University of Uzbekistan, 4 University Str., Tashkent 100174, Republic of Uzbekistan

Abduvali A.Khaldjigitov: Samarkand branch of Tashkent University of Information Technologies, 100140, Sh. Mirzo str. 47-a Samarkand, Uzbekistan

Abstract
The numerical investigations have been carried out on reinforced concrete slab against blast loading to demonstrate the accuracy and effectiveness of the finite element based numerical models using commercial package ABAQUS. The response of reinforced concrete slab have been studied against the influence of weight of TNT, standoff distance, boundary conditions, influence of air blast and surface blast. The results thus obtained from simulations were compared with the experiments available in literature. The inelastic behavior of concrete and steel reinforcement bar has been incorporated through concrete damage plasticity model and Johnson-cook models available in ABAQUS were presented. The predicted results through numerical simulations of the present study were found in close agreement with the experimental results. The damage mechanism and stress response of target were assessed based on the intensity of deformations, impulse velocity, von-Mises stresses and damage index in concrete. The results indicate that the standoff distance has great influence on the survivability of RC slab against blast loading. It is concluded that the velocity of impulse wave was found to be decreased from 17 to 11 m/s when the mass of TNT is reduced from 12 to 6 kg. It is observed that the maximum stress in the concrete was found to be in the range of 15 to 20 N/mm2 and is almost constant for given charge weight. The slab with two short edge discontinuous end condition was found better and it may be utilised in designing important structures. Also it is observed that the deflection in slab by air blast was found decreased by 60% as compared to surface blast.

Key Words
reinforced concrete slab; damages; blast loading; mass of TNT; finite element analysis; deformation

Address
K. Senthil, A. Singhal and B. Shailja: Department of Civil Engineering, Dr. B R Ambedkar National Institute of Technology Jalandhar, Jalandhar, Punjab 144011, India

Abstract
A numerical simulation of the incompressible multiphase hydraulic jump flow was performed to compare the interface prediction through the use of the three RANS turbulence models: k–ɛ, RNGk– ɛ and SST k–w. A three dimensional no submerged hydraulic jump and a two dimensional submerged hydraulic jump were modeled. Both the geometry and the mesh were created using the open source Gmsh code. The project\'s geometry consists of a rectangular channel with length and height differences between the two dimensional and three dimensional simulations. Uniform hexahedral cells were used for the mesh. Three refining meshes were constructed to allow to verify simulation convergence. The Volume of Fluid (abbr. VOF) method was used for treatment of the air-water surface. The turbulence models were evaluated in three distinct set up configurations to provide a greater accuracy in the flow representation. In the two-dimensional analysis of a submerged hydraulic jump simulation, the turbulence model RNG RNG k– ɛ provided a better interface adjust with the experimental results than the model k– ɛ and SST k–w. In the three-dimensional simulation of a no-submerged hydraulic jump the k–# showed better results than the SST k–w and RNG k– ɛ capturing the height and length of the ledge with a better fit with the experimental results.

Key Words
fluid-flow interface; turbulence model; hydraulic jump; multiphase flow

Address
Raquel J. Lobosco, David O. da Fonseca and Necesio G. Costa: Themal and Fluids Laboratory, Rio de Janeiro Federal University, Macaé Campus, Brazil

raziella M. F. Jannuzzia: Field Testing and Instrumentation Laboratory Prof Márcio Miranda Soares,
COPPE and Rio de Janeiro Federal University, Macaé Campus, Brazil

Abstract
The present work investigates the use of a rigid rocking block as a tool to reduce vibrations in a frame structure. The study is based on a simplified model composed by a 2-DOF linear system, meant to represent a general M-DOF frame structure, coupled with a rocking rigid block through a linear visco-elastic device, which connects only the lower part of the 2-DOF system. The possibility to restrain the block directly to the ground, by means of a second visco-elastic device, is investigated as well. The dynamic response of the model under an harmonic base excitation is then analysed in order to evaluate the effectiveness of the coupling in reducing the displacements and the drift of the 2-DOF system. The nonlinear equations of motion of the coupled assemblage 2-DOF-block are obtained by a Lagrangian approach and then numerically integrated considering some reference mechanical and geometrical quantities as variable parameters. It follows an extensive parametric analysis, whose results are summarized through behaviour maps, which portray the ratio between the maximum displacements and drifts of the system, with and without the coupling with the rigid block, for several combinations of system\'s parameters. When the ratio of the displacements is less than unity, the coupling is considered effective. Results show that the presence of the rocking rigid block improves the dynamics of the system in large ranges of the characterizing parameters.

Key Words
visco-elastic coupling, rocking rigid block, harmonic excitation, gain coefficients and maps

Address
Angelo Di Egidio, Stefano Pagliaro, Cristiano Fabrizio and Andrea M. de Leo: DICEAA - University of L\'Aquila, via G. Gronchi, 18-67100 L\'Aquila, Italy


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