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CONTENTS
Volume 52, Number 1, October10 2014
 

Abstract
An interfacial penny-shaped crack between piezoelectric layer and elastic half-space subjected to mechanical and electric loads is investigated. Using Hankel transform technique, the mixed boundary value problem is reduced to a system of singular integral equations. The integral equations are further reduced to a system of algebraic equations with the aid of Jacobi polynomials. The stress intensity factor and energy release rate are determined. Numerical results reveal the effects of electric loadings and material parameters of composite on crack propagation and growth. The results seem useful for design of the piezoelectric composite structures and devices of high performance.

Key Words
interfacial crack; penny-shaped crack; Hankel transform; energy release rate; piezoelectric material

Address
J.H. Ren, Y.S. Li and W. Wang: College of Mechanical and Electrical Engineering, Hebei University of Engineering, Handan 056038, P.R. China

Abstract
Structural robustness refers to the ability of a structure to avoid disproportionate consequences to the original cause. Currently attentions focus on the concepts of structural robustness, and discussions on methods of robustness based structural design are rare. Firstly, taking basis in robust H norm of the system transfer function. Then using the SIMP material model, robustness based design of grid structures is formulated as a continuum topology optimization problem, where the relative density of each element and structural robustness are considered as the design variable and the optimization objective respectively. Generalized elitist genetic algorithm is used to solve the optimization problem. As examples, robustness configurations of plane stress model and the rectangular hyperbolic shell model were obtained by robustness based structural design. Finally, two models of single-layer grid structures were designed by conventional and robustness based method respectively. Different interference scenarios were simulated by static and impact experiments, and robustness of the models were analyzed and compared. The results show that the H structural robustness index can indicate whether the structural response is proportional to the original cause. Robustness based structural design improves structural robustness effectively, and it can provide a conceptual design in the initial stage of structural design.

Key Words
structural robustness; robustness based structural design; grid structures; topology optimization; experimental verification

Address
Hui Wu: School of Business Administration, Zhejiang University of Finance & Economics, 18 Xueyuan Street, Hangzhou, China
Cheng Zhang: Civil Department, East China Electric Power Design Institute, 409 Wuning Road, Shanghai, China
Bo-qing Gao and Jun Ye: College of Civil Engineering and Architecture, Zhejiang University, 866 Yuhangtang Road, Hangzhou, China

Abstract
This paper studies the behaviour of deteriorated reinforced concrete (RC) beams attacked by various forms of simulated acid rain. An artificial rainfall simulator was firstly designed and evaluated. Eleven RC beams (120 mmx200 mmx1800 mm) were then constructed in the laboratory. Among them, one was acting as a reference beam and the others were subjected to three accelerated corrosion methods, including immersion, wetting-drying, and artificial rainfall methods, to simulate the attack of real acid rain. Acid solutions with pH levels of 1.5 and 2.5 were considered. Next, ultrasonic, scanning electron microscopy (SEM), dynamic, and three-point bending tests were performed to investigate the mechanical properties of concrete and flexural behaviour of the RC beams. It can be concluded that the designed artificial simulator can be effectively used to simulate the real acid rainfall. Both the immersion and wetting-drying methods magnify the effects of the real acid rainfall on the RC beams.

Key Words
acid deposition; reinforced concrete beam; deterioration; flexural strength; corrosion depth

Address
Yingfang Fan, Haiyang Luan, Dawei Wang: Institute of Road and Bridge Engineering, Dalian Maritime University, Dalian 116026, China
Zhiqiang Hu: School of Hydraulic Engineering, Dalian University of Technology, Dalian 116023, China
An Chen: Department of Civil Engineering, University of Idaho, Idaho 441022, USA

Abstract
A three-dimensional finite element model for the Jiashao Bridge, the longest multi-span cablestayed bridge in the world, is established using the commercial software package ANSYS. Dynamic characteristics of the bridge are analyzed and the effects of structural system measures including the rigid hinge, auxiliary piers and longitudinal constraints between the girders and side towers on the dynamic properties including modal frequency, mode shape and effective mass are studied by referring to the Jiashao Bridge. The analysis results reveal that: (i) the installation of the rigid hinge significantly reduces the modal frequency of the first symmetric lateral bending mode of bridge deck. Moreover, the rigid hinge significantly changes the mode shape and effective mass of the first symmetric torsional mode of bridge deck; (ii) the layout of the auxiliary piers in the side-spans has a limited effect on changing the modal frequencies, mode shapes and effective masses of global vibration modes; (iii) the employment of the longitudinal constraints significantly increases the modal frequencies of the vertical bending modes and lateral bending modes of bridge deck and have significant effects on changing the mode shapes of vertical bending modes and lateral bending modes of bridge deck. Moreover, the effective mass of the first anti-symmetric vertical bending of bridge deck in the longitudinal direction of the fully floating system is significantly larger than that of the partially constrained system and fully constrained system. The results obtained indicate that the structural system measures of the multi-span cable-stayed bridge have a great effect on the dynamic properties, which deserves special attention for seismic design and wind-resistant design of the multi-span cable-stayed bridge.

Key Words
multi-span cable-stayed bridge; dynamic characteristics; rigid hinge; longitudinal constraint; auxiliary pier

Address
Fangfang Geng, Youliang Ding, Hongen Xie: Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, Southeast University, Nanjing 210096, China
Jianyong Song and Wanheng Li: Research Institute of Highway Ministry of Transport, Beijing 100088, China

Abstract
To analyze the tension performance of laminated rubber bearings under tensile loading, a theoretical tension model for analyzing the rubber bearings is proposed based on the theory of elasticity. Applying the boundary restraint condition and the assumption of incompressibility of the rubber (Poisson\'s ratio of the rubber material is about 0.5 according the existing research results), the stress and deformation expressions for the tensile rubber layer are derived. Based on the derived expressions, the stress distribution and deformation pattern especially for the deformation shapers of the free edges of the rubber layer are analyzed and validated with the numerical results, and the theory of cracking energy is applied to analyze the distributions of prediction cracking energy density and gradient direction. The prediction of crack initiation and crack propagation direction of the rubber layers is investigated. The analysis results show that the stress and deformation expressions can be used to simulate the stress distribution and deformation pattern of the rubber layer for laminated rubber bearings in the elastic range, and the crack energy method of predicting failure mechanism are feasible according to the experimental phenomenon.

Key Words
laminated rubber bearing; isolation; deformation; tension model; finite element method

Address
Shicai Chen, Tongya Wang, Weiming Yan, Zhiqian Zhang: Department of Civil Engineering, Beijing University of Technology, Pingleyuan 100, Chaoyang, Beijing 100124, China
Kang-Suk Kim: Department of Civil Engineering, Tsinghua University, Qinghuayuan 1, Beijing 100084, China

Abstract
We analyze the buckling of a thin elastic plate due to intrinsic stresses in thin films attached to the surfaces of the plate. In the case of cylindrical buckling, it is shown that for a plate with clamped edges compressive intrinsic film stresses can cause flexural buckling of the plate, while tensile intrinsic film stresses cannot. For a plate with free edges, film intrinsic stresses, compressive or tensile, cannot cause buckling.

Key Words
cylindrical buckling; elastic plate; thin film; intrinsic stress

Address
J. Zhu: College of Mechanical Engineering, Zhejiang University of Technology, Hangzhou 310032, China
J.S. Yang: Department of Engineering Mechanics, University of Nebraska, Lincoln, NE 68588-0526, USA
C.Q. Ru: Department of Mechanical Engineering, University of Alberta, Edmonton, Alberta, Canada

Abstract
In the present work appropriate concrete material models have been proposed to predict drying shrinkage and specific creep of High-performance concrete (HPC) using Artificial Neural Network (ANN). The ANN models are trained, tested and validated using 106 different experimental measured set of data collected from different literatures. The developed models consist of 12 input parameters which include quantities of ingredients namely ordinary Portland cement, fly ash, silica fume, ground granulated blastfurnace slag, water, and other aggregate to cement ratio, volume to surface area ratio, compressive strength at age of loading, relative humidity, age of drying commencement and age of concrete. The Feed-forward backpropagation networks with Levenberg-Marquardt training function are chosen for proposed ANN models and same implemented on MATLAB platform. The results shows that the proposed ANN models are more rational as well as computationally more efficient to predict time-dependent properties of drying shrinkage and specific creep of HPC with high level accuracy.

Key Words
artificial neural network, high performance concrete, prediction models, drying shrinkage, specific creep

Address
Banti A. Gedam, N.M. Bhandari and Akhil Upadhyay: Civil Engineering Department, Indian Institute of Technology - Roorkee, Uttarakhand 247667, India

Abstract
In this study, an extended Kantorovich method, employing multi-term displacement functions, is applied to analyze the vibration problem of symmetrically laminated plates with arbitrary boundary conditions. The vibration behaviors of laminated plates are determined based on the variational principle of total energy minimization and the iterative Kantorovich method. The out-of-plane displacement is represented in the form of a series of a sum of products of functions in x and y directions. With a known function in the x or y directions, the formulation for the variation of total potential energy is transformed to a set of governing equations and a set of boundary conditions. The equations and boundary conditions are then numerically solved for the natural frequency and vibration mode shape. The solutions are verified with available solutions from the literature and solutions from the Ritz and finite element analysis. In most cases, the natural frequencies compare very well with the reference solutions. The vibration mode shapes are also very well modeled using the multi-term assumed displacement function in the terms of a power series. With the method used in this study, it is possible to solve the angle-ply plate problem, where the Kantorovich method with single-term displacement function is ineffective.

Key Words
vibration; natural frequency; laminated plate; extended Kantorovich method; various boundary conditions

Address
Pairod Singhatanadgid and Thanawut Wetchayanon: Department of Mechanical Engineering, Faculty of Engineering, Chulalongkorn University, Pathumwan, Bangkok 10330, Thailand

Abstract
The present paper deals with the first ply failure analysis of the laminated composite plates under various static and dynamic loading conditions. Static analysis has been carried out under patch load and triangular load. The dynamic failure analysis has been carried out under triangular pulse load. The formulation has been carried out using the finite element method and a computer code has been developed. The first order shear deformation theory has been applied in the present formulation. The displacement time history analysis of laminated composite plate has been carried out and the results are compared with those published in literature to validate the formulation. The first ply failure load for laminated composite plates with various lamination schemes under static and dynamic loading conditions has been calculated using various failure criteria. The failure index-time history analysis has also been carried out and presented in this paper.

Key Words
laminated composites; first ply failure; pulse load, finite element; dynamic failure

Address
Chaitali Ray and Somnath Majumdera: Department of Civil Engineering, Indian Institute of Engineering Science and Technology, Shibpur (Formerly Bengal Engineering and Science University, Shibpur), Howrah - 711103, India

Abstract
Four algorithms for damage detection of trusses are presented in this paper. These approaches can detect damage by using both complete and incomplete measurements. The suggested methods are based on the minimization of the difference between the measured and analytical static responses of structures. A non-linear constrained optimization problem is established to estimate the severity and location of damage. To reach the responses, the successive quadratic method is used. Based on the objective function, the stiffness matrix of the truss should be estimated and inverted in the optimization procedure. The differences of the proposed techniques are rooted in the strategy utilized for inverting the stiffness matrix of the damaged structure. Additionally, for separating the probable damaged members, a new formulation is proposed. This scheme is employed prior to the outset of the optimization process. Furthermore, a new tactic is presented to select the appropriate load pattern. To investigate the robustness and efficiency of the authors\' method, several numerical tests are performed. Moreover, Monte Carlo simulation is carried out to assess the effect of noisy measurements on the estimated parameters.

Key Words
damage assessment; updated matrix; Sherman-Morrison-Woodbury formula; truss structure; optimization; Monte Carlo simulation; incomplete measurement

Address
M. Rezaiee-Pajand and M.S. Kazemiyana: Department of Civil Engineering, Ferdowsi University of Mashhad, Azadi Sq., Mashhad, Khorasan Razavi, Iran

Abstract
The cross-section warping due to the passage of high-speed trains can be a relevant issue to consider in the dynamic analysis of bridges due to (i) the usual layout of railway systems, resulting in eccentric moving loads; and (ii) the use of cross-sections prone to warping deformations. A thin-walled beam formulation for the dynamic analysis of bridges including the cross section warping is presented in this paper. Towards a numerical implementation of the beam formulation, a finite element with seven degrees of freedom is proposed. In order to easily consider the compatibility between elements, and since the coupling between flexural and torsional effects occurs in non-symmetric cross-sections due to dynamic effects, a single axis is considered for the element. The coupled flexural-torsional free vibration of thin-walled beams is analysed through the presented beam model, comparing the results with analytical solutions presented in the literature. The dynamic analysis due to an eccentric moving load, which results in a coupled flexuraltorsional vibration, is considered in the literature by analytical solutions, being therefore of a limited applicability in practice engineering. In this paper, the dynamic response due to an eccentric moving load is obtained from the proposed finite element beam model that includes warping by a modal analysis.

Key Words
thin-walled beam dynamics; warping; eccentric moving load; lateral-torsional vibrations

Address
Ricardo F. Vieira, Diego Lisi and Francisco B. Virtuoso:
Department of Civil Engineering, Arquitecture and Georesources, Instituto Superior Técnico,
Universidade de Lisboa, Av. Rovisco Pais 1049-001 Lisboa, Portugal

Abstract
This paper is concerned with the modification of multidisciplinary feasible formulation for MDO problems using the integrated coupled approximate models. A drawback of conventional MDFs is the numerical difficulty in decomposing the design variables and deriving the coupled equations of state. To overcome such a drawback of conventional methods, the coupling in analysis and design is resolved by approximating the state variables in each discipline by the response surface method and by modifying the optimization formulation using the corresponding integrated coupled approximate models. The validity, reliability and effectiveness of the proposed method are illustrated and verified through two optimization problems, a mathematical MDF problem and the multidisciplinary optimum design of suspension unit of wheeled armored vehicle.

Key Words
multidisciplinary design optimization (MDO); successive iterative design; Integrated coupled approximate model; response surface method; wheeled armored vehicle

Address
Eun-Ho Choi, Jin-Rae Cho and O-Kaung Lim: School of Mechanical Engineering, Pusan National University, Busan 609-735, Korea


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