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CONTENTS
Volume 55, Number 1, July10 2015
 

Abstract
This article presents a theoretical parametric analysis on the ultimate torsional behaviour of axially restrained reinforced concrete (RC) beams. This analysis is performed by using a computing procedure based on a modification of the Variable Angle Truss Model. This computing procedure was previously developed to account for the influence of the longitudinal compressive stress state due to the axial restraint conditions provided by the connections of the beams to other structural members. The presented parametric study aims to check the influence of some important variable studies, namely: torsional reinforcement ratio, compressive concrete strength and axial restraint level. From the results of this parametric study, nonlinear regression analyses are performed and some design charts are proposed. Such charts allow to correct the resistance torque of RC beams (rectangular sections with small height to width ratios) to account for the favorable influence of the axial restraint.

Key Words
reinforced concrete; beams; torsion; axial restraint; parametric study; torsional design

Address
Luis F.A. Bernardo, Catia S.B. Taborda: Department of Civil Engineering and Architecture, Centre of Materials and Building Technologies (C-made), University of Beira Interior, Covilha, Portugal
Jorge M.R. Gama: Departments of Mathematics, University of Beira Interior, Center of Mathematics, Covilha, Portugal

Abstract
A three-dimensional (3-D) method of analysis is presented for determining the natural frequencies of a truncated shallow and deep conical shell with linearly varying thickness along the meridional direction free at its top edge and clamped at its bottom edge. Unlike conventional shell theories, which are mathematically two-dimensional (2-D), the present method is based upon the 3-D dynamic equations of elasticity. Displacement components ur, uo and uz in the radial, circumferential, and axial directions, respectively, are taken to be periodic in o and in time, and algebraic polynomials in the r and z directions. Strain and kinetic energies of the truncated conical shell with variable thickness are formulated, and the Ritz method is used to solve the eigenvalue problem, thus yielding upper bound values of the frequencies by minimizing the frequencies. As the degree of the polynomials is increased, frequencies converge to the exact values. Convergence to four-digit exactitude is demonstrated. The frequencies from the present 3-D method are compared with those from other 3-D finite element method and 2-D shell theories.

Key Words
truncated conical shell; vibration; variable thickness; three-dimensional analysis

Address
Department of Architectural Engineering, Chung-Ang University, 221 Heuksuk-Dong, Dongjak-Ku, Seoul, 156-756, Republic of Korea

Abstract
This paper presents the effect of hybridization material on variation of critical buckling load with different cross-ply laminates plate resting on elastic foundations of Winkler and Pasternak types subjected to combine uniaxial and biaxial loading by using two variable refined plate theories. Governing equations are derived from the principle of virtual displacement; the formulation is based on a new trigonometric shape function of displacement taking into account transverse shear deformation effects vary parabolically across the thickness satisfying shear stress free surface conditions. These equations are solved analytically using the Navier solution of a simply supported. The influence of the various parameters geometric and material, the thickness ratio, and the number of layers symmetric and antisymmetric hybrid laminates material has been investigated to find the critical buckling loads. The numerical results obtained through the present study with several examples are presented to verify and compared with other models with the ones available in the literature.

Key Words
buckling; hybrid, cross-ply laminates; winkler and pasternak; elastic foundation; two variables plate theory

Address
Khadidja Benselama, Noureddine El Meiche, El Abbas Adda Bedia: Laboratoire des Materiaux et Hydrologie, Universite Djillali Liabes, Sidi Bel Abbes, Algerie
Abdelwahed Tounsi: Department de Genie Civil, Faculte de Technologie, Universite Djillali Liabes, Sidi bel Abbes, Algerie

Abstract
In recent years, implants have gained growing importance in all areas of medicine. The success of the treatment depends on many factors affecting the bone-implant, implant-abutment and abutment-prosthesis interfaces. In this paper, static and dynamic behaviors of the dental prosthesis are investigated. Three-dimensional finite element models of dental prosthesis were constructed. Dynamic loads in 5 sec applied on occlusal surface. Therefore, FEA was selected for use in this study to examine the effect of the static and dynamic loads on the stress distribution for an implant-supported fixed partial denture and supporting bone tissue.

Key Words
static and dynamic loading; finite element analysis; dental prosthesis

Address
N. Djebbar, B. Serier and B. Bachir Bouiadjrab: Department of Mechanical Engineering, University of Sidi Bel Abbes, BP 89, Cite Ben M\'hidi, Sidi Bel Abbes 22000, Algeria

Abstract
In this study, free vibration analyses of symmetric laminated cantilever and simply supported damaged composite beams are investigated by using finite element method (FEM). Free vibration responses of damaged beams are examined using Euler Bernoulli beam and classical lamination theories. A computer code is developed by using MATLAB software to determine the natural frequencies of a damaged beam. The local damage zone is assumed to be on the surface lamina of the beam by broken fibers after impact. The damaged zone is modeled as a unidirectional discontinuous lamina with 0o orientations in this study. Fiber volume fraction (vf), fiber aspect ratio (Lf/df), damage length (LD) and its location (y/L), fiber orientation and stacking sequence parameters effects on natural frequencies are investigated. These parameters are affected the natural frequency values significantly.

Key Words
fiber reinforced composites; finite element method (FEM); structural design; vibration/vibration control

Address
Yusuf Cunedioglu: Faculty of Engineering, Mechanical Engineering Department, Nigde University, 51245, Campus, Nigde, Turkey
Bertan Beylergil: Faculty of Engineering, Mechanical Engineering Department, Izmir Institute of Technology, 35437, Gulbahce Campus, Izmir, Turkey

Abstract
Finite element analysis (FEA) combined with the concepts of linear elastic fracture mechanics (LEFM) provides a practical and convenient means to study the fracture and crack growth of materials. In this paper, a numerical modeling of crack propagation in the cement mantle of the reconstructed acetabulum is presented. This work is based on the implementation of the displacement extrapolation method (DEM) and the strain energy density (SED) theory in a finite element code. At each crack increment length, the kinking angle is evaluated as a function of stress intensity factors (SIFs). In this paper, we analyzed the mechanical behavior of cracks initiated in the cement mantle by evaluating the SIFs. The effect of the defect on the crack propagation path was highlighted.

Key Words
strain energy density; mixed mode; crack propagation; orthopedic cement

Address
Benouis Ali and Serier Boualem: Mechanics and Physics of Materials Laboratory, Djillali Liabes University of Sidi Bel-Abbes, BP89 cite Larbi Ben M\'hidi, Sidi Bel-Abbes, Algeria
Boulenouar Abdelkader: Materials and Reactive Systems Laboratory, Mechanical Engineering Department, University of Sidi-Bel-Abbes, BP. 89, City Larbi Ben Mhidi, Sidi Bel Abbes 22000, Algeria
Benseddiq Noureddine: Mechanics Laboratory of Lille, CNRS UMR 8107, Ecole Polytech

Abstract
Bridge behavior under passing traffic loads has been studied for the past 50 years. This paper presents how to model congestion on bridges and how the maximum dynamic stress of bridges change during the passing of moving vehicles. Most current research is based on mid-span dynamic effects due to traffic load and most bridge codes define a factor called the dynamic load allowance (DLA), which is applied to the maximum static moment under static loading. This paper presents an algorithm to solve the governing equation of the bridge as well as the equations of motions of two real European trucks with different speeds, simultaneously. It will be shown, considering congestion in eight case studies, the maximum dynamic stress and how far from the mid-span it occurs during the passing of one or two trucks with different speeds. The congestion effect on the maximum dynamic stress of bridges can make a significant difference in the magnitude. By finite difference method, it will be shown that where vehicle speeds are considerably higher, for example in the case of railway bridges which have more than one railway line or in the case of multiple lane highway bridges where congestion is probable, current designing codes may predict dynamic stresses lower than actual stresses; therefore, the consequences of a full length analysis must be used to design safe bridges.

Key Words
bridge; dynamics; congestion; maximum dynamic stress; stress analysis; finite difference method; DLA (dynamic load allowance)

Address
Kianoosh Samanipour and Hassan Vafai: Department of Civil Engineering, Sharif University of Technology, Tehran, Iran

Abstract
The one-way (two-way) flexural strength of RCC prisms (circular slabs) reinforced with glass fiber textiles is addressed. To this end, alkaline-resistant glass fiber textiles with three surface weights were used in the composite, the matrix concrete was designed with zero/nonzero slump, and the textiles were used with/without an intermediate layer provided by epoxy resin and sand mortar. Prisms were tested under a four-point loading apparatus and circular slabs were placed on simple supports under a central load. Effects of the amount and geometry of reinforcement, matrix workability, and the intermediate layer on the ultimate load and deflection were investigated. Results revealed that, with a specific reinforcement amount, there is an optimum textile tex for each case, depending on the matrix mix design and the presence of intermediate layer. Similar results were obtained in one-way and two-way bending tests.

Key Words
RCC pavements; TRC; glass fiber textile; flexural strength

Address
Morteza Madhkhan and Saeid Nowroozi: Department of Civil Engineering, Isfahan University of Technology, Isfahan, 8415683111, Iran
Mohammad E. Torki: Department of Aerospace Engineering, Texas A&M University, College Station, TX 77843, USA

Abstract
Soil-pile raft-structure interaction is recognized as a significant phenomenon which influences the seismic behaviour of structures. Soil structure interaction (SSI) has been extensively used to analyze the response of superstructure and piled raft through various modelling and analysis techniques. Major drawback of previous study is that overall interaction among entire soil-pile raft-superstructure system considering highlighting the change in design forces of various components in structure has not been explicitly addressed. A recent study addressed this issue in a broad sense, exhibiting the possibility of increase in pile shear due to SSI. However, in this context, relative stiffness of raft and that of pile with respect to soil and length of pile plays an important role in regulating this effect. In this paper, effect of relative stiffness of piled raft and soil along with other parameters is studied using a simplified model incorporating pile-soil raft and superstructure interaction in very soft, soft and moderately stiff soil. It is observed that pile head shear may significantly increase if the relative stiffness of raft and pile increases and furthermore stiffer pile group has a stronger effect. Outcome of this study may provide insight towards the rational seismic design of piles.

Key Words
seismic base shear; pile-raft-structure interaction; raft flexibility; flexibility of piles; pile shear; column shear

Address
Rajib Saha: Civil Engineering Department, National Institute of Technology Agartala (NIT Agartala), Barjala, Jirania 799046, India
Sekhar C. Dutta: Department of Civil Engineering, Indian School of Mines, Dhanbad, Dhanbad 826004, Jharkhand, India
Sumanta Haldar: School of Infrastructure, Indian Institute of Technology (IIT Bhubaneswar), Samantapuri, Bhubaneswar 751 013, Odisha, India

Abstract
Control of the mechanical behavior of composite materials and structures under monotonic and dynamic loads for cracks and damage is a vast and complex area of research. The modeling of the different physical phenomena and behavior characteristics of a composite material during deformation play an important role in the structural design. Our study aims to analyze numerically the energy release rate parameter G of a composite laminated plate (glass or boron / epoxy) cross-ply [+a, −a] in the presence of a crack between two circular notches under the effect of several parameters such as fiber orientation a, the crack orientation B, the orientation y of the two considered circular notches and the effect of mechanical properties. Our results show clearly that both notches orientation has more effect on G than the cracks and fibers orientations.

Key Words
cracks; rate of energy restitution; fibers orientations; finite element method and laminates

Address
Habib Achache and Benali Boutabout: Laboratory of Mechanical and Physical of Materials (LMPM), University Djillali Liabes of Sidi Bel Abbes, BP 89, Street Ben M\'Hidi, Sidi Bel Abbes, Algeria
Abdelouahab Benzerdjeb: University of Science and Technology Oran Mohammed Boudiaf (USTO), BP1505 El Menaouar, 31036 Oran, Algeria
Djamel Ouinas: Laboratory of Numerical and experimental modeling of mechanical phenomena, University of Mostaganem, Route Belahcel 27000 Mostaganem, Algeria

Abstract
The results of a numerical investigation pertaining to the hysteretic behaviour of concrete filled steel tubular (CFT) column to I-beam connections are discussed in detail. Following the verification of the numerical results against the available experimental tests, the nonlinear finite element (FE) analysis was implemented to evaluate the effects of different parameters including the column axial load, beam lateral support, shape and arrangement of stiffeners, stiffness of T-stiffeners, and the number of shear stiffeners. Pursuing this objective, an external CFT column to beam connection, tested previously, was selected as the case-study. The lateral forces on the structure were simulated, albeit approximately, using an incremental cyclic loading reversal applied at the beam tip. The results were compared in terms of hysteretic load-displacement curves, stress distributions in connection, strength, rotation, and energy dissipation capacity. It was shown that external T-stiffeners combined with internal shear stiffeners play an important role in the hysteretic performance of CFT columns to I-beam connections.

Key Words
CFT columns; steel I-beam; column to beam connections; seismic performance; hysteretic behaviour; cyclic loading

Address
R. Esfandyary: Department of Civil Engineering, Azad University, South Tehran Branch, Tehran, Iran
M.S. Razzaghi: Department of Civil Engineering, Azad University, Qazvin Branch, Qazvin, Iran
A. Eslami: School of Civil Engineering, The University of Queensland, Australia

Abstract
H-infinity norm relates to the maximum in the frequency response function and H-infinity control method focuses on the case that the vibration is excited at the fundamental frequency, while 2-norm relates to the output energy of systems with the input of pulses or white noises and 2-norm control method weighs the overall vibration performance of systems. The trade-off between the performance in frequency-domain and that in time-domain may be achieved by integrating two indices in the mixed vibration control method. Based on the linear fractional state space representation in the modal space for a piezoelectric flexible structure with uncertain modal parameters and un-modeled residual high-frequency modes, a mixed dynamic output feedback control design method is proposed to suppress the structural vibration. Using the linear matrix inequality (LMI) technique, the initial populations are generated by the designing of robust control laws with different H-infinity performance indices before the robust 2-norm performance index of the closed-loop system is included in the fitness function of optimization. A flexible beam structure with a piezoelectric sensor and a piezoelectric actuator are used as the subject for numerical studies. Compared with the velocity feedback control method, the numerical simulation results show the effectiveness of the proposed method.

Key Words
uncertain structures; LMI; mixed vibration control; modal space; fitness function

Address
Yalan Xu, Yu Qian and Jianjun Chen: School of Electronic & Mechanical Engineering, Xidian University, Xi\'an 710071, PR China
Gangbing Song: Department of Mechanical Engineering, University of Houston, Houston, TX 77004, USA


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