- Volume:4 Issue:1, 2013
- تاریخ انتشار: 1392/06/25
- تعداد عناوین: 6
This paper deals with local buckling analysis of rectangular functionally graded material plates using finite strip method and based on classical plate theory. The modulus of elasticity of the plate is assumed to vary according to a power-law distribution in terms of the volume fractions of the constituents. The principle of minimum total potential energy is employed to obtain stiffness and stability matrices of functionally graded plate while a matrix eigenvalue problem is then solved to find the critical stresses of rectangular plates subjected to various types of loading including uniform and non-uniform uniaxial loadings and biaxial uniform loading. The accuracy of the proposed model is validated in which the obtained results are compared with those reported elsewhere. Furthermore, a comprehensive parametric study is performed to investigate the effects of various parameters such as boundary conditions, power law index, aspect ratio and type of loading on the local buckling coefficient of functionally graded material plates whilst the developed finite strip method is also employed to study the buckling behaviour of long stiffened functionally graded plates subjected to uniform uniaxial loading.
Validation and application of empirical shear wave velocity models based on standard penetration testPages 25-41
Shear wave velocity is a basic engineering tool required to define dynamic properties of soils. In many instances it may be preferable to determine Vs indirectly by common in-situ tests, such as the Standard Penetration Test. Many empirical correlations based on the Standard Penetration Test are broadly classified as regression techniques. However, no rigorous procedure has been published for choosing the models. This paper provides 1) a quantitative comparison of the predictive performance of empirical correlations; 2) a reproducible method for choosing the coefficients of previous empirical methods based on the particle swarm optimization and 3) taking into account the polynomial correlation, a new model proposed. Different empirical correlations are compared with different validation criteria. The best performing empirical correlationsresult in a new modeland the unique coefficient associated determined by particle swarm optimization concluded. The more recent correlation only marginally improves prediction accuracy; thus, efforts should focus on improving data collection.
In this paper, a crack localization method for Euler-Bernoulli beams via an efficient static data based indicator is proposed. The crack in beams is simulated here using a triangular variation in the stiffness. Static responses of a beam are obtained by the finite element modeling. In order to reduce the computational cost of damage detection method, the beam deflection is fitted through a polynomial function using a limited number of nodal displacements. A damage indicator based on static responses obtained for healthy and damaged structure is proposed to identify the damage. Three test examples including a simply supported beam, an overhanging beam and an indeterminate beam are considered. The influence of many parameters may affect the efficiency of the method such as the number of elements, the value, type and location of applied load as well as the noise effect is investigated. Numerical results show that, the locations of single and multiple damage cases having different characteristics can be well determined by the method proposed.
In recent years, the trend in solving optimization problems has been directed toward using heuristic algorithms such as neural networks, genetic and ant colony algorithms. The main reason for this trend can be attributed to the fact that these algorithms can be efficiently adjusted to the specific search space to which they are applied and consequently they can be used for many optimization problems of different nature. In this paper, the behavior of classical ACS algorithm in finding collapse load factor of two-dimensional frames is investigated closely. Time consuming and redundant parts that greatly affect the performance are removed leading to an accelerated ACS algorithm called variant one in this work. For some frames with certain combination of plastic moments and loadings the first variant does not lead to acceptable results. Therefore a few constraints intended to accelerate the variant one of ACS algorithm are eliminated and some provisions are added to bias the solution toward ant decision making strategy rather than problem dependent information. Consequently a new variant called variant two is proposed that can be used for a wider range of frames with of course more computational effort.
A simulated annealing approach to solve the network design of one-way streets: case of Shiraz networkPages 83-101
This study is devoted to the formulation of the network design problem of one-way streets and the application of simulated annealing (SA) algorithm to solve this problem for a large real network. It discusses some points of views on one-way street networks, the objective function used for design, the way in which design constraints may be considered, and the traffic problems concerning one-way streets. The results of applying the method to a real network are compared with the respective results of another heuristic approach of alternative one-way network generation, to test the goodness of SA algorithm. The SA solution to the problem became superior to any other solution at hand. Moreover, the question of the necessity of using the true values of the parameters of volume-delay functions, definition of “projects” (street segments), as well as the sufficiency of morning peak demand for design, are dealt with. Suggestions for further research end the discussion.
Nonlinear inelastic static analysis of plane frames with numerically generated tangent stiffness matricesPages 103-117
For the nonlinear analysis of structures using the well known Newton-Raphson Method, the tangent stiffness matrices of the elements must be constructed in each iteration. Due to the high expense required to find the exact tangent stiffness matrices, researchers have developed novel innovations into the Newton-Raphson method to reduce the cost and time required by the analysis. In this paper, a new approach is suggested to generate the tangent stiffness matrix numerically from internal forces for the materially nonlinear analysis of structures. The method is organized at the element level and, as is verified by numerical experiments, affords good stability and preserves the convergence rate near that of the original exact Newton-Raphson version. To implement the method, an appropriate configuration is first sought for the stiffness matrix of the finite element, which satisfies the element equilibrium requirement; then, the entries of this matrix template are generated from the generalized internal forces of the element by the numerical method of finite differences. The method is applied to construct the stiffness matrix of the plane frame element, which will be used in the analysis of some sample frame structures with materially nonlinear behavior, under monotonic static loading.