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CONTENTS
Volume 28, Number 1, July10 2018
 

Abstract
In this paper, local ratcheting behavior of 1045 steel plates with circular cutout was investigated. Experimental tests were carried out by a Zwick/Roell HB 100 servo hydraulic machine. In order to measure the local strain at notch root, a data acquisition system with strain gauge was used. Various notch diameters and distances of strain gauges mounted from the notch root were found influential in the magnitude of local ratcheting strain. It was found that the local maximum principal stress plays a crucial role in increasing the local plastic deformation. Numerical simulation was done by ABAQUS software using nonlinear isotropic/kinematic hardening model. Material parameters of hardening model were attained from several stabilized cycles of flat specimens subjected to symmetric strain cycles. The nonlinear kinematic hardening model along with the Neuber's rule was employed to assess local ratcheting at the notch root of steel plates. The results of the numerical simulations agreed closely with those measured values in this study. Both ratcheting progress and mean stress relaxation occurred simultaneously at the notch root.

Key Words
local ratcheting behavior; notch root; nonlinear isotropic/kinematic hardening model; Neuber's rule; 1045 steel plates

Address
(1) K. Kolasangiani, K. Farhangdoost, M. Shariati:
Department of Mechanical Engineering, Ferdowsi University of Mashhad, Azadi Square, Mashhad, Iran;
(2) A. Varvani-Farahani:
Department of Mechanical and Industrial Engineering, Ryerson University, Victoria Street, Toronto, Canada.

Abstract
A size-dependent novel hyperbolic shear deformation theory of simply supported functionally graded beams is presented in the frame work of the non-local strain gradient theory, in which the stress accounts for only the nonlocal strain gradients stress field. The thickness stretching effect (εz ≠ 0) is also considered here. Elastic coefficients and length scale parameter are assumed to vary in the thickness direction of functionally graded beams according to power-law form. The governing equations are derived using the Hamilton principle. The closed-form solutions for exact critical buckling loads of nonlocal strain gradient functionally graded beams are obtained using Navier's method. The derived results are compared with those of strain gradient theory.

Key Words
new hyperbolic shear theory; nonlocal strain gradient elasticity; stretching effect; buckling analysis

Address
(1) Mohammed Sid Ahmed Houari, Aicha Bessaim, Abdelouahed Tounsi:
Laboratoire des Structures et Matériaux Avancés dans le Génie Civil et Travaux Publics, Université de Sidi Bel Abbes, Faculté de Technologie, Département de génie civil, Algeria;
(2) Mohammed Sid Ahmed Houari, Aicha Bessaim:
Département de génie civil, Faculté des Sciences et de la Technologie, Université de Mascara, Route de Mamounia 29000 Mascara, Algérie;
(3) Mohammed Sid Ahmed Houari, Aicha Bessaim, Abdelouahed Tounsi:
Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria;
(4) Fabrice Bernard:
Université Européenne de Bretagne, INSA Rennes, LGCGM, 20 avenue des Buttes de coësmes 35708 Rennes Cedex 7, France;
(5) Abdelouahed Tounsi:
Civil and Environmental Engineering Department, King Fahd University of Petroleum & Minerals, Dhahran, Saudi Arabia;
(6) Abdelouahed Tounsi:
Laboratoire de Modélisation et Simulation Multi-échelle, Département de Physique, Faculté des Sciences Exactes, Département de Physique, Université de Sidi Bel Abbés, Algeria;
(7) S.R. Mahmoud:
Department of Mathematics, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia.

Abstract
For the first time, the parametric instability characteristics of tow-steered variable stiffness composite laminated (VSCL) cylindrical panels is investigated using B-spline finite strip method (FSM). The panel is considered containing geometrical defects including cutout and delamination. The material properties are assumed to vary along the panel axial length of any lamina according to a linear fiber-orientation variation. A uniformly distributed inplane longitudinal loading varies harmoni-cally with time is considered. The instability load frequency regions corresponding to the assumed in-plane parametric load-ing is derived using the Bolotin's first order approximation through an energy approach. In order to demonstrate the capabili-ties of the developed formulation in predicting stability behavior of the thin-walled VSCL structures, some representative results are obtained and compared with those in the literature wherever available. It is shown that the B-spline FSM is a proper tool for extracting the stability boundaries of perforated delaminated VSCL panels.

Key Words
parametric stability; higher order shear deformation theory; variable stiffness curved panel; cutout; delamination

Address
Aeronautical Science and Technology Department, Aerospace Research Institute, Mahestan St., Shahrek-e-gharb, Tehran, P.O. Box 14665-834, Iran.


Abstract
The concrete bridge decks are usually precast and in-situ assembled with steel girders with post-pouring joint in the construction practice of super-wide steel-concrete composite beam. But the difference of concrete age between the precast slabs and the post-pouring joint has been not yet considered for the long-term performance analysis of this kind composite beam. A simply supported precast-assembled T-shaped beam was taken as an example to analyze the long-term performance of steel-concrete composite beam with post-pouring joint. Based on the deformation coordination conditions of the old-new concrete deck and steel girder, a theoretical model for the long-term behavior of precast-assembled composite beam is proposed in this paper according to age-adjusted effective modulus method. Then, the feasibility of the proposed model is verified by the available test data from the Gilbert's composite beams. Parametric studies were preformed to evaluate the influences of the cross-sectional area ratio of the post-pouring joint to the whole bridge deck, as well as the difference of concrete age between the precast slabs and the post-pouring joint, on the long-term performance of the composite beam. The results indicate that the traditional method without considering the age difference would seriously underestimate the effect of creep and shrinkage of concrete bridge decks. The concrete age difference between the precast slabs and the post-pouring joint should be demonstrated for the life cycle design and long-term performance analysis of precast-assembled steel-concrete composite beams.

Key Words
composite beam; precast-assembled; post-pouring joint; shrinkage; creep; assembled age

Address
School of Civil Engineering, Central South University, Changsha, Hunan, 410075, China.


Abstract
A new I-girder consisted of top concrete-filled tubular flange and corrugated web has been proved to have high resistance to both global buckling of the entire girder and local buckling of the web. This study carries out theoretical analysis and experimental tests for this new I-girder to investigate the stress distribution in the flanges and in the corrugated web. Based on some reasonable assumptions, theoretical equations for calculating the normal stress in the flanges and the shear stress in the corrugated web are presented. To verify the accuracy of the presented equations, experimental tests on two specimens were carried out, and the experimental results of stress distribution were used to assess the theoretical prediction. Comparison between the two results indicates that the presented theoretical equations have enough accuracy for calculating the stress in the new Igirder, and thus they can be used reliably in the design stage.

Key Words
I-girder; concrete-filled tubular flange; corrugated web; stress distribution; theoretical equations

Address
School of Civil Engineering and Architecture, Southwest Petroleum University, Chengdu, 610500, PR China.


Abstract
This paper reports an experimental study that was accomplished to assess the seismic behavior of steel tube reinforced concrete bridge columns (SBCs). The motivation of this study was to verify a supposition that the core steel tube may be terminated at a rational position in the column to minimize the material cost while maintaining the seismic behavior of this composite column. Four SBC specimens were tested under combined constant axial load and cyclic reversed lateral loads. The unique variable in the test matrix was the core steel tube embedment length, which ranged from 1/3 to 3/3 of the column effective height. It is observed that SBCs showed two distinctly different failure patterns, namely brittle shear failure and ductile flexural failure. Tests results indicate that the hysteretic responses of SBCs were susceptible to the core steel tube embedment length. With the increase of this structural parameter, the lateral strength of SBC was progressively improved; the deformability and ductility, however, exhibited a tendency of first increase and then decrease. It is also found that in addition to maintained the rate of stiffness degradation and cumulative energy dissipation basically unchanged, both the ductility and deformability of SBC were significantly improved when the core steel tube was terminated at the mid-height of the column, and these were the most unexpected benefits accompanied with material cost reduction.

Key Words
bridge column; seismic behavior; economy; core steel tube; embedment length; cyclic loading

Address
School of Civil Engineering, Dalian University of Technology, Dalian, P.R. China.


Abstract
This paper experimentally and analytically elucidates the shear behavior and shear bearing capacity of partially prefabricated steel reinforced concrete (PPSRC) columns and hollow partially prefabricated steel reinforced concrete (HPSRC) columns. Seven specimens including five PPSRC column specimens and two HPSRC column specimens were tested under static monotonic loading. In the test, the influences of shear span aspect ratio and difference of cast-in-place concrete strength on the shear behavior of PPSRC and HPSRC columns were investigated. Based on the test results, the failure pattern, the loaddisplacement behavior and the shear capacity were focused and analyzed. The test results demonstrated that all the column specimens failed in shear failure mode with high bearing capacity and good deformability. Smaller shear span aspect ratio and higher strength of inner concrete resulted in higher shear bearing capacity, with more ductile and better deformability. Furthermore, calculation formula for predicting the ultimate shear capacity of the PPSRC and HPSRC columns were proposed on the basis of the experimental results.

Key Words
prefabricated structure; steel reinforced concrete column; experimental study; shear behavior; shear capacity

Address
School of Civil Engineering, Xi'an University of Architecture & Technology, Xi'an, Shaanxi 710055, China.


Abstract
This research was conducted to study the behavior of exterior concrete beam-column joints with reinforced shape memory alloy (SMA) bars tested under cyclic loading. These bars benefit from superelastic behavior and can stand high loads without residual strains. The experimental part of the study, 8 specimens of exterior concrete beam-column joints were made and tested. Two different types of concrete with 30 and 45 MPa were used. Four specimens contained SMA bars and 4 specimens contained steel bars in beam-column joints. Furthermore, different transverse reinforcements were used in beams investigate the effects of concrete confinement. Specimens were tested under cyclic loading. Results show that SMA bars are capable of recentering to their original shape after standing large displacements. Due to the superelastic behavior of SMA bars, cracks at the joint core vanish under cyclic loading. As the cyclic loading increased, bending failure occurred in the beam outside the joint core. In the analytical parts of the study, specimens were simulated using the SeismoStruct software. Experimental and analytical results showed a satisfactory correlation. Plastic hinge length at the beam joint for specimens with SMA and steel bars was calculated by empirical equations, experimental and analytical results. It was shown that Paulay's and Priestley's equations are appropriate for concrete beam-column joints in both types of bars.

Key Words
Shape Memory Alloy (SMA); reinforced concrete; beam-column joints; superelastic effect; cyclic loading

Address
Department of Civil Engineering, Ferdowsi University of Mashhad, Mashhad, Iran.


Abstract
In this paper, a new size-dependent quasi-3D plate theory is presented for wave dispersion analysis of functionally graded nanoplates while resting on an elastic foundation and under the hygrothermaal environment. This quasi-3D plate theory considers both thickness stretching influences and shear deformation with the variations of displacements in the thickness direction as a parabolic function. Moreover, the stress-free boundary conditions on both sides of the plate are satisfied without using a shear correction factor. This theory includes five independent unknowns with results in only five governing equations. Size effects are obtained via a higher-order nonlocal strain gradient theory of elasticity. A variational approach is adopted to owning the governing equations employing Hamilton\'s principle. Solving analytically via Fourier series, these equations gives wave frequencies and phase velocities as a function of wave numbers. The validity of the present results is examined by comparing them with those of the known data in the literature. Parametric studies are conducted for material composition, size dependency, two parametric elastic foundation, temperature and moisture differences, and wave number. Some conclusions are drawn from the parametric studies with respect to the wave characteristics.

Key Words
functionally graded materials; wave propagation; quasi-3D plate theory; higher-order nonlocal strain gradient elasticity theory; hygrothermal environment

Address
(1) Behrouz Karami, Maziar Janghorban, Davood Shahsavari:
Department of Mechanical Engineering, Marvdasht Branch, Islamic Azad University, Marvdasht, Iran;
(2) Abdelouahed Tounsi:
Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria.

Abstract
It has been argued that fracture energy of composite laminates depends on their thickness and number of layers. In this paper a modified direct energy balance approach (DEBA) has been developed to evaluate the mode-II shear fracture energy for E-glass/Epoxy laminates from finite element model at an arbitrary thickness. This approach considers friction and damage/plasticity deformations using cohesive zone modeling (CZM) and nonlinear finite element modeling. The presence of compressive stress and resulting friction was argued to be a possible cause for the thickness dependency of fracture energy. In the finite element modeling, CZM formulation has been developed with bilinear cohesive constitutive law combined with friction consideration. Also ply element have been developed with shear plastic damage model. Modified direct energy balance approach has been proposed for estimation of mode-II shear fracture energy. Experiments were performed on laminates of glass epoxy specimens for characterization of material parameters and determination of mode-II fracture energies for different thicknesses. Effect of laminate thickness on fracture energy of transverse crack tension (TCT) and end notched flexure (ENF) specimens has been numerically studied and comparison with experimental results has been made. It is shown that the developed numerical approach is capable of estimating increase in fracture energy due to size effect.

Key Words
composite; fracture energy; finite element method; Mode-II shear; damage

Address
(1) M. Saeed Goodarzi:
Department of Industrial, Mechanical and Aerospace Engineering, Buein Zahra Technical University, Buein Zahra, Qazvin, Iran;
(2) Hossein Hosseini-Toudeshky:
Department of Aerospace Engineering, Amirkabir University of Technology, No. 424, Hafez Ave. Tehran, Iran.


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