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CONTENTS
Volume 38, Number 5, June10 2011
 

Abstract
This paper presents analytical solutions for skewed thick plates under transverse loading that have previously been unreported in the literature. The thick plate solution is obtained in a framework of an oblique coordinate system. The governing equation is first derived in the oblique coordinate system, and the solution is obtained using deflection and rotation as partial derivatives of a potential function developed in this research. The solution technique is applied to three illustrative application examples, and the results are compared with numerical solutions in the literature and those derived from the commercial finite element analysis package ANSYS 11. These results are in excellent agreement. The present solution may also be used to model skewed structures such as skewed bridges, to facilitate efficient routine design or evaluation analyses, and to form special elements for finite element analysis. At the same time, the analytical solution developed in this research could be used to develop methods to address post-buckling and dynamic problems.

Key Words
skewed plates; thick plates; Mindlin theory; analytical functions; first order shear deformation theory

Address
Pang-jo Chun: Department of Civil and Environmental Engineering, Ehime University, Matsuyama, Japan
Gongkang Fu: Department of Civil and Environmental Engineering, Wayne State University, Detroit, USA; College of Civil Engineering, Tongji University, Shanghai, China; College of Civil Engineering, Fuzhou University, Fuzhou, China
Yun Mook Lim: Department of Civil and Environmental Engineering, Yonsei University, Seoul, Korea

Abstract
Comprehensive and accurate analysis of a finite foundation beam is a challenging engineering problem and an important subject in foundation design. One of the limitation of the traditional Winkler elastic foundation model is that the model neglects the effect of the interface resistance between the beam and the underneath foundation soil. By taking the beam-soil interface resistance into account, a deformation governing differential equation for a finite beam resting on the Winkler elastic foundation is developed. The coupling effect between vertical and horizontal displacements is also considered in the presented method. Using Galerkin method, semi-analytical solutions for vertical and horizontal displacements, axial force, shear force and bending moment of the beam under symmetric loads are presented. The influences of the interface resistance on the behavior of foundation beam are also investigated.

Key Words
foundation beam; Winkler model; deformation-coupling; interface resistance; nonlinear analysis; Galerkin method.

Address
L. Zhang: College of Civil Engineering, Hunan University, Changsha, 410082, China
M.H. Zhao: College of Civil Engineering, Hunan University, Changsha, 410082, China
Y. Xiao: College of Civil Engineering, Hunan University, Changsha, 410082, China; Department of Civil Engineering University of Southern California, Los Angeles, CA 90089-2531, USA
B.H. Ma: College of Civil Engineering, Hunan University, Changsha, 410082, China

Abstract
This paper deals with the problem of the determination of the response of a viscoelastic Bernoulli-Navier beam, which is resting on an elastic medium. Assuming uniaxial bending, the displacement of the beam axis is governed by an integro-differential equation. The compatibility of the displacements between the beam and the elastic medium is imposed through an integral equation. In general and in particular in the case of a Boussinesq medium, the solution has to be pursued numerically. On the contrary, in the case of a Winkler\'s medium the compatibility equation becomes a linear finite relationship, which allows finding an original analytical solution of the problem for both hereditary and aging behavior of the beam. Some numerical examples complete the paper, in which a comparison is made between the hereditary and the aging model for the creep of the beam.

Key Words
beams; creep; analytical solution; contact problem; Winkler

Address
Claudio Floris and Francesco Paolo Lamacchi: Department of Structural Engineering, Politecnico di Milano, I-20133 Milano, Italy

Abstract
This paper provides a complex variable BIE for solving the periodic notch problems in plane plasticity. There is no limitation for the configuration of notches. For the periodic notch problem, the remainder estimation technique is suggested. In the technique, the influences on the central notch from many neighboring notches are evaluated exactly. The influences on the central notch from many remote notches are approximated by one term with a multiplying factor. This technique provides an effective way to solve the problems of periodic structures. Several numerical examples are presented, and most of them have not been reported previously.

Key Words
complex variable BIE; periodic notch problem; remainder estimation technique; stress concentration.

Address
Y.Z. Chen: Division of Engineering Mechanics, Jiangsu University, Zhenjiang, Jiangsu, 212013, P.R. China

Abstract
The paper presents a study aimed at understanding some characteristics of an interior explosion within a room with limited or no venting. The explosion may occur in ammunition storage or result from a terrorist action or from a warhead that had penetrated into this room. The study includes numerical simulations of the problem and analytical derivations. Different types of analysis (1-D, 2-D and 3-D analysis) were performed for a room with rigid walls and the results were analyzed. For the 3D problem the effect of the charge size and its location within the room was investigated and a new insight regarding the pressure distribution on the interior wall as function of these parameters has been gained. The numerical analyses were carried out using the Eulerian multi-material approach. Further, an approximate analytical formula to predict the residual internal pressure was developed. The formula is based on the conservation law of total energy and its implementation yields very good agreement with the results obtained numerically using the complete statement of the problem for a wide range of explosive weights and room sizes that is expressed through a non-dimensional parameter. This new formula is superior to existing literature recommendations and compares considerably better with the above numerical results.

Key Words
confined explosion; shock wave; wave reflection; peak pressure; residual pressure.

Address
V.R. Feldgun, Y.S. Karinski and D.Z. Yankelevsky: National Building Research Institute, Technion-IIT, Haifa, Israel

Abstract
This paper presents a novel method for predicting the failure probability of structural or mechanical systems subjected to random loads and material properties involving multiple design points. The method involves Multicut High Dimensional Model Representation (Multicut-HDMR) technique in conjunction with moving least squares to approximate the original implicit limit state/performance function with an explicit function. Depending on the order chosen sometimes truncated Cut-HDMR expansion is unable to approximate the original implicit limit state/performance function when multiple design points exist on the limit state/performance function or when the problem domain is large. Multicut-HDMR addresses this problem by using multiple reference points to improve accuracy of the approximate limit state/performance function. Numerical examples show the accuracy and efficiency of the proposed approach in estimating the failure probability.

Key Words
structural reliability; weight function; high dimensional model representation; multiple design points; failure probability.

Address
Rajib Chowdhury: School of Engineering, Swansea University, Singleton Park, Swansea, UK
B.N. Rao: Structural Engineering Division, Department of Civil Engineering, Indian Institute of Technology Madras,
Chennai – 600 036, India

Abstract
It is difficult to accurately predict the flexural strength of prestressed members with unbonded tendons, unlike that of prestressed members with bonded tendons, due to the unbonded behavior between concrete and tendon. While there have been many studies on this subject, the flexural strength of prestressed members with unbonded tendons is still not well understood, and different standards in various countries often result in different estimation results for identical members. Therefore, this paper aimed to observe existing approaches and to propose an improved model for the ultimate strength of prestressed members with unbonded tendons. Additionally, a large number of tests results on flexural strength of prestressed members with unbonded tendons were collected from previous studies, which entered into a database to verify the accuracy of the proposed model. The proposed model, compared to existing approaches, well estimated the flexural strength of prestressed members with unbonded tendons, adequately reflecting the effects of influencing factors such as the reinforced steel ratio, the loading patterns, and the concrete strength. The proposed model also provided a reasonably good estimation of the ultimate strength of over-reinforced members and high-strength concrete members.

Key Words
prestressed; post-tension; unbonded; prestressing tendon; flexural strength.

Address
Deuck Hang Lee and Kang Su Kim: Department of Architectural Engineering, University of Seoul, Seoul, Korea


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