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CONTENTS
Volume 34, Number 3, February20 2010
 

Abstract
The two-dimensional deformation of a homogeneous, isotropic thermoelastic half-space with voids with variable modulus of elasticity and thermal conductivity subjected to thermomechanical boundary conditions has been investigated. The formulation is applied to the coupled theory(CT) as well as generalized theories: Lord and Shulman theory with one relaxation time(LS), Green and Lindsay theory with two relaxation times(GL) Chandrasekharaiah and Tzou theory with dual phase lag(C-T) of thermoelasticity. The Laplace and Fourier transforms techniques are used to solve the problem. As an application, concentrated/uniformly distributed mechanical or thermal sources have been considered to illustrate the utility of the approach. The integral transforms have been inverted by using a numerical inversion technique to obtain the components of displacement, stress, changes in volume fraction field and temperature distribution in the physical domain. The effect of dependence of modulus of elasticity on the components of stress, changes in volume fraction field and temperature distribution are illustrated graphically for a specific model. Different special cases are also deduced.

Key Words
thermoelasticity; generalized thermoelasticity; modulus of elasticity; thermal conductivity; thermal relaxation parameters; concentrated/uniformly distributed source; integral transforms.

Address
Rajneesh Kumar: Department of Mathematics, Kurukshetra University, Kurukshetra-136119, India
Savita Devi: Department of Mathematics, D.N. College, Hisar-125001, India

Abstract
This paper studies the reliability of an analytical tool for predicting the lateral loaddeformation response of RC columns while subjected to lateral cyclic displacements and axial load. The analytical tool in this study is based on a fiber element model implemented into the program DRAIN- 2DX (fiber element). The response of RC column under cyclic displacement is defined by the behavior of concrete, and reinforcing steel under general reversed-cyclic loading. A tri-linear stress-strain relationship for the cyclic behavior of steel is proposed and the improvement in the analytical results is studied. This study only considers the behavior of columns with flexural dominant mode of failure. It is concluded that with the implementation of appropriate constitutive material models, the described analytical tools can predict the response of the columns with reasonable accuracy when compared to experimental data.

Key Words
reinforced concrete; cyclic loading; analytical; fiber element; column; non-linear; constitutive model.

Address
R. Sadjadi: Department of Civil Engineering, Ryerson University, Toronto, Ontario, Canada
M.R. Kianoush: Department of Civil Engineering, Ryerson University, Toronto, Ontario, Canada

Abstract
The dynamic response of a finite Bernoulli-Euler beam resting on a tensionless Pasternak foundation and subjected to a concentrated harmonic load is investigated in this study. This load may be applied at the center of the beam, or it may be offset from the center. Since the elastic foundation is assumed to be tensionless, the beam may lift off the foundation, resulting in contact and non-contact regions in the system. An analytical/numerical solution is obtained from the governing equations of the contact and non-contact regions to determine the coordinates of the lift-off points. Although there is no nonlinear term in the equations, the problem appears to be nonlinear since the contact regions are not known in advance. Due to that nonlinearity, the essentials of the problem (the coordinates of the lift-off points) are calculated numerically using the Newton-Raphson technique. The results, which represent the symmetric and asymmetric responses of the beam, are presented graphically in this work. They illustrate the effects of the forcing frequency and the beam length on the extent of the contact regions and displacements.

Key Words
finite beam; Pasternak foundation; lift-off; harmonic load.

Address
Irfan Coskun: Faculty of Civil Engineering, Yildiz Technical University, Davutpasa Campus, 34210 Esenler, Istanbul, Turkey

Abstract
Out of plane behaviors of walls and infills are investigated in this paper, using rigid block concepts. Walls and infills are sometimes separated from top beams because of in plane movement of the walls and crumbling mortar layers under the top beams. Therefore, sufficient strength should be supplied to hold them against out of plane forces. Such walls are studied here under some real and scaled earthquakes, regarding their out of plane behavior. Influences of some reinforcements, connecting the walls to frames or perpendicular walls, are also studied. It is shown that unreinforced walls of regular sizes (3 m high and 4.5 m long) are normally unstable in the earthquakes. However, performing some reinforced bars that connect them to adjacent elements- frames or perpendicular walls - stabilizes them. Eventually, it is concluded that supplying 3 reinforced bars at 1/4, 2/4 and 3/4 of the panel\'s height stabilizes the walls in the assumed earthquakes. In this regard, for 20 cm and 35 cm thick walls o18mm and o20mm bars are to be used, respectively. For walls with other configurations, the forces and required areas of the reinforcements can be determined by the developed method of this paper.

Key Words
rigid block; wall; infill; out of plane; seismic behavior; reinforcement.

Address
Mohammadi Gh.M.: International Institute of Earthquake Engineering and Seismology (IIEES), No. 21, Arghavan gharbi, Dibaji shomali, Dr. Lavasani St., Tehran, I.R. Iran
Yasrebi F.: International Institute of Earthquake Engineering and Seismology (IIEES), No. 21, Arghavan gharbi, Dibaji shomali, Dr. Lavasani St., Tehran, I.R. Iran

Abstract
A novel system identification and structural health assessment procedure of steel framed structures with semi-rigid connections is presented in this paper. It is capable of detecting damages at the local element level under normal operating conditions; i.e., serviceability limit state. The procedure is a linear time-domain system identification technique in which the structure responses are required, whereas the dynamic excitation force is not required to identify the structural parameters. The procedure tracks changes in the stiffness properties of all the elements in a structure. It can identify damage-free and damaged structural elements very accurately when excited by different types of dynamic loadings. The method is elaborated with the help of several numerical examples. The results indicate that the proposed algorithm identified the structures correctly and detected the pre-imposed damages in the frames when excited by earthquake, impact, and harmonic loadings. The algorithm can potentially be used for structural health assessment and monitoring of existing structures with minimum disruption of operations. Since the procedure requires only a few time points of response information, it is expected to be economic and efficient.

Key Words
structural health assessment; semi-rigid connections; system identification; unknown dynamic force.

Address
Hasan N. Katkhuda: Civil Engineering Department, The Hashemite University, Zarqa 13115, Jordan
Hazim M. Dwairi: Civil Engineering Department, The Hashemite University, Zarqa 13115, Jordan
Nasim Shatarat: Civil Engineering Department, The Hashemite University, Zarqa 13115, Jordan

Abstract
In this paper, an experimental investigation of the mechanical behavior and buckling failure of sharp-notched circular tubes subjected to cyclic bending is discussed. The unnotched and sharp-notched circular tubes of SUS 304 stainless steel were tested under symmetric curvature-controlled cyclic bending. It was found from moment-curvature curves that the loops show cyclic hardening and gradually steady after a few cycles for all tested tubes. The ovalization-curvature curves show an unsymmetric, ratcheting and increasing manner with the number of cycles. In addition, it was found that six almost parallel lines corresponding to unnotched and five different notch-depth (0.2, 0.4, 0.6, 0.8 and 1.0 mm) tubes were noted from the experimental relationship between the cyclic controlled curvature and the number of cycles necessary to produce buckling on a log-log scale. An empirical formulation was proposed so that it could be used for simulating the aforementioned relationship. By comparing with the experimental finding, the simulation was in good agreement with the experimental data.

Key Words
mechanical behavior; buckling failure; sharp-notched circular tubes; cyclic bending; moment; ovalization; number of cycles to produce bucking.

Address
Kuo-Long Lee: Department of Computer Application Engineering, Far East University, Tainan, Taiwan 701, R.O.C.

Abstract
This paper studies fracture initiation direction of two parallel non-coplanar cracks of equal length. Using the dislocation pile-up modelling, singular integral equations for two parallel cracks subjected to mixed-mode loading are derived and the crack-tip field including singular and non-singular terms is obtained. The kinking angle is determined by using the maximum hoop stress criterion, or the e-criterion. Results are presented for simple uniaxial tension and biaxial loading. The biaxiality ratio has a noticeable influence on crack growth direction. For the case of biaxial tension, when neglecting the Tstress the crack branching angle is overestimated for small crack inclination angles relative to the largest applied principal stress direction, and underestimated for large crack inclination angles.

Key Words
crack kinking angle; T-stress; crack growth; biaxiality ratio.

Address
X.-F. Li: School of Civil Engineering and Architecture, Central South University, Changsha 410075, China
B.-Q. Tang: School of Mathematics and Computational Science, Changsha University of Science and Technology,
Changsha 410114, China
X.-L. Peng: School of Civil Engineering and Architecture, Central South University, Changsha 410075, China
Y. Huang: School of Civil Engineering and Architecture, Central South University, Changsha 410075, China

Abstract


Key Words


Address
Liu Lipeng: School of Transportation Science and Technology, Harbin Institute of Technology, Harbin 150090, China
Wang Zonglin: School of Transportation Science and Technology, Harbin Institute of Technology, Harbin 150090, China
Zhai Changhai: School of Civil Engineering, Harbin Institute of Technology, Harbin 150090, China
Zhai Ximei: School of Civil Engineering, Harbin Institute of Technology, Harbin 150090, China

Abstract


Key Words
curvature effect; plate waves; curved steel plate; guided waves; dispersion curves.

Address
Juwon Lee: Department of Ocean Engineering, Pukyong National University, Busan 608-737, Korea
Won-Bae Na: Department of Ocean Engineering, Pukyong National University, Busan 608-737, Korea
Jeong-Tae Kim: Department of Ocean Engineering, Pukyong National University, Busan 608-737, Korea


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