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Virtual Work (virtual + work)
Selected AbstractsElastic and inelastic drift performance optimization for reinforced concrete buildings under earthquake loadsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 8 2004Chun-Man Chan Abstract This paper presents an effective optimization technique for the elastic and inelastic drift performance design of reinforced concrete buildings under response spectrum loading and pushover loading. Attempts have been made to develop an automatic optimal elastic and inelastic drift design of concrete framework structures. The entire optimization procedure can be divided into elastic design optimization and inelastic design optimization. Using the principle of virtual work, the elastic drift response generated by the response spectrum loading and the inelastic drift response produced by the non-linear pushover loading can be explicitly expressed in terms of element sizing design variables. The optimization methodology for the solution of the explicit design problem of buildings is fundamentally based on the Optimality Criteria approach. One ten-story, two-bay building frame example is presented to illustrate the effectiveness and practicality of the proposed optimal design method. While rapid convergence in a few design cycles is found in the elastic optimization process, relatively slow but steady and smooth convergence of the optimal performance-based design is found in the inelastic optimization process. Copyright © 2004 John Wiley & Sons, Ltd. [source] Stress intensity factors for cracked triangular cross-section thin-walled tubesFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 12 2004Y. J. XIE ABSTRACT For one kind of finite-boundary crack problems, the cracked equilateral triangular cross-section tube, an analytical and very simple method to determine the stress intensity factors has been proposed based on a new concept of crack surface widening energy release rate and the principle of virtual work. Different from the classical crack extension energy release rate, the crack surface widening energy release rate can be defined by the G*-integral theory and expressed by stress intensity factors. This energy release rate can also be defined easily by the elementary strength theory for slender structures and expressed by axial strains and loads. These two forms of crack surface widening energy release rate constitute the basis of a new analysis method for cracked tubes. From present discussions, a series of stress intensity factors are derived for cracked equilateral triangular cross-section tubes. Actually, the present method can also be applied to cracked polygonal tubes. [source] A second-order homogenization procedure for multi-scale analysis based on micropolar kinematicsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 12 2007Ragnar Larsson Abstract The paper presents a higher order homogenization scheme based on non-linear micropolar kinematics representing the macroscopic variation within a representative volume element (RVE) of the material. On the microstructural level the micro,macro kinematical coupling is introduced as a second-order Taylor series expansion of the macro displacement field, and the microstructural displacement variation is gathered in a fluctuation term. This approach relates strongly to second gradient continuum formulations, presented by, e.g. Kouznetsova et al. (Int. J. Numer. Meth. Engng 2002; 54:1235,1260), thus establishing a link between second gradient and micropolar theories. The major difference of the present approach as compared to second gradient formulations is that an additional constraint is placed on the higher order deformation gradient in terms of the micropolar stretch. The driving vehicle for the derivation of the homogenized macroscopic stress measures is the Hill,Mandel condition, postulating the equivalence of microscopic and macroscopic (homogenized) virtual work. Thereby, the resulting homogenization procedure yields not only a stress tensor, conjugated to the micropolar stretch tensor, but also the couple stress tensor, conjugated to the micropolar curvature tensor. The paper is concluded by a couple of numerical examples demonstrating the size effects imposed by the homogenization of stresses based on the micropolar kinematics. Copyright © 2006 John Wiley & Sons, Ltd. [source] Numerical issues in the virtual fields methodINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 10 2004Michel Grédiac Abstract This paper deals with the direct identification of parameters governing anisotropic elastic constitutive equations. These parameters are identified from heterogeneous strain fields with the virtual fields method. This method is based on a relevant use of the principle of virtual work. Different numerical aspects of the implementation of the method are discussed in the paper, mainly in terms of stability of the identified parameters when noisy data are processed. It is shown that the sensitivity of the method to noisy data is compatible with a practical use during experiments. Copyright © 2004 John Wiley & Sons, Ltd. [source] The role of relationships in understanding telecommuter satisfactionJOURNAL OF ORGANIZATIONAL BEHAVIOR, Issue 3 2006Timothy D. Golden Relationships are fundamental to organizational functioning, yet as telecommuting and other forms of virtual work become increasingly popular, research has not yet focused on how the virtual context might alter relationships so as to impact important work outcomes. This study therefore examines the role relationships play in mediating the link between the extent of telecommuting and job satisfaction. In doing so three fundamental types of relationships maintained by employees are investigated,those with managers, coworkers, and family. Regression analysis of field data from 294 telecommuting employees in a large telecommunications company revealed the anticipated inverted U-shaped relationship, mediated by leader-member exchange quality, team-member exchange quality, and work-family conflict. Copyright © 2006 John Wiley & Sons, Ltd. [source] An exact sinusoidal beam finite elementPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2008Zdzislaw Pawlak The purpose of the paper is to derive an efficient sinusoidal thick beam finite element for the static analysis of 2D structures. A two,node, 6,DOF curved, sine,shape element of a constant cross,section is considered. Effects of flexural, axial and shear deformations are taken into account. Contrary to commonly used curvilinear co,ordinates, a rectangular co,ordinates system is used in the present analysis. First, an auxiliary problem is solved: a symmetric clamped,clamped sinusoidal arch subjected to unit nodal displacements of both supports is considered using the flexibility method. The exact stiffness matrix for the shear,flexible and compressible element is derived. Introduction of two parameters "n" and "t" enables the identification of shear and membrane influences in the element stiffness matrix. Basing on the principle of virtual work a full set of 18 shape functions related to unit support displacements is derived (total rotations of cross,sections, tangential and normal displacements along the element). The functions are found analytically in the closed form. They are functions of one linear dimensionless coordinate of x,axis and depend on one geometrical parameter of sinusoidal arch, height/span ratio "c" and on physical and geometrical properties of the element cross,section. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Finite element analysis of land subsidence above depleted reservoirs with pore pressure gradient and total stress formulationsINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 4 2001Giuseppe Gambolati Abstract The solution of the poroelastic equations for predicting land subsidence above productive gas/oil fields may be addressed by the principle of virtual works using either the effective intergranular stress, with the pore pressure gradient regarded as a distributed body force, or the total stress incorporating the pore pressure. In the finite element (FE) method both approaches prove equivalent at the global assembled level. However, at the element level apparently the equivalence does not hold, and the strength source related to the pore pressure seems to generate different local forces on the element nodes. The two formulations are briefly reviewed and discussed for triangular and tetrahedral finite elements. They are shown to yield different results at the global level as well in a three-dimensional axisymmetric porous medium if the FE integration is performed using the average element-wise radius. A modification to both formulations is suggested which allows to correctly solve the problem of a finite reservoir with an infinite pressure gradient, i.e. with a pore pressure discontinuity on its boundary. Copyright © 2001 John Wiley & Sons, Ltd. [source] | ||||||||||