فصلنامه مدل سازی در مهندسی
پیاپی 20 (بهار 1389)

Concrete arch dams required less volume of concrete, when they are designed by an optimized geometrical model. These types of structures have better resistance against earthquakes because they are light, and can be built with lower prices. Optimal dam model should include all the features of the geometric, physical and mechanical specifications in the analysis. In this study, the authors use several geometric models for optimizing the shape of arch dams and will choose the most effective one. Dam volume is used as the objective function and geometric and behavior constraints are utilized for better adjustment to the nature of structure. Finite element method and feasible sequential quadratic programming are used for the analysis, and optimal shapes of several dams are obtained. The results show that parabolic model, in addition to having a minimum body volume, requires fewer numbers of optimization iterations in comparison to the other's geometrical forms.

High strength to weight ratio is significant specific of sandwich panels due to trait particular of special structure of them. The variables that defined for design of sandwich panels should be determined with procedure that it has lowest weight with appropriate strength. Due to this reason, utilization of optimization algorithms to design of these panels has a particular importance. Particle swarm optimization (PSO) algorithm is a random method that is adopted from nature for solving couple and multi objective problems in engineering. In this paper the application of this method in weight optimization of prismatic core sandwich panels based on yield and buckling criteria is proposed. Because of the PSO algorithm, doesnt need the derivative and special preliminary guess and also is a random procedure, this algorithm is able to search the extended solving space with appropriate probability. Comparison of results represented that PSO algorithm in few iterates can achieve to better results.

In this researches the effect of masonry infill in concrete frames behavior have been proceed by two three strut and diagonal one strut, that three strut method is known as one of last presented Technique for infill masonry modeling so diagonal one strut method is suggested method of retrofit construction for modeling of masonry infills. Three aspects of frames that have been investigated are height (number of story), thickness and modeling method of infills. These frames have been loaded and analyzed based on 519 & 2800 codes. and designed according to ninth discussion of structures public (national) institutes and then analyzed based on nonlinear pushover analysis in two state with and without infill by sap 2000 software, and the amount of masonries infill effect on the frames behavior has been investigated. The results represents that infills increase, strength, stiffness and improve performance level and decrease of hinges number, but in most of analysis states, infills have been destroyed completely and diagonal one strut method in most cases represented conservative results rather than three strut method for frames. Amount of stiffness increment and drift decrease, because of infill presence would be decrease by increase in height. By this, ignorance of infills in lower fames can result in incorrect design and increase of infills thickness did not have such influence on the improve of studied frames behavior in this research.

Nowadays, Voltage stability is an important types of power system stabilities. To analysis of voltage stability, different static and dynamic boundaries such as maximum Loadability point (MLP) and bifurcation points such as saddle node bifurcation (SNB), hopf bifurcation (HB) and limit induced bifurcation (LIB) are introduced. Bifurcation theory that is based on the eigenvalue analysis is an effective method to evaluation of voltage stability and its boundaries. Moreover, load models, over-excitation limits of generators and auto-regulator of transformers will affect voltage stability. Therefore, in this paper, the Hopf bifurcation boundary of voltage stability feasible region is analyzed by combination of time domain simulation (TDS), bifurcation theory and modal analysis of dynamic Jacobian matrix of power system. Effect of different load models, reactive power generation limits of generators and excitation system parameters on voltage stability dynamic loading margin (especially HB) is evaluated.

Trapezoidal open channels are among the most common and optimized sections that used in water conveyance system. Thus investigation of flow conditions in them is very essential. One of the most important related subjects is lateral velocity component that produced cells in secondary flow. Several parameters such as channel roughness can intervene on how cells were formed. In the present study applying CFD methods using ANSYS CFX package flow condition in trapezoidal open channels with roughed boundary were simulated and variation of cells in secondary flow and distribution of hydraulic parameters such as mean depth velocity and boundary shear stress under uniform increase of boundary roughness were investigated. The results showed changes in sizes as well as the cells location due to uniform roughness increase. Also this increase was caused decrease in mean depth velocity and increase in boundary shear stress.

Eventful sections prioritization methods usually have been based on single-criterion methods. Therefore, with respect to a separate and distinct criterion, identifying and prioritization of different sections have been done. Due to budget deficiency for immunization actions, prioritization non-immune sections are of great importance. In this regard, several different methods were presented by experts that were based on a specific basis. Among these, we can point to two general structures based on economic and technical studies. On the other hand due to weakness in accidents data (incomplete, incorrect or unused data), It is better to identify and prioritize the proposed methods, evaluated as far as possible without regard to the accidents data, here the new and innovative methods have special significance. In this study which is new in the field of road immune in the country, we use powerful device named multilayer Artificial Neural Networks for predicting prioritization of eventful MAZANDARAN road networks modifying. And tried to investigate the advantages of using neural networks, considering the history of accidents and the costs of their modifying, achieving method to optimal prioritization should be analyzed.

Neural network is a powerfull tool to predict the behavior and response of systems in engineering area. In present work, the time dependent results of experimental investigations have processed with a neural network model. Neural network model was Feed-Forward and has used the Levenberg-Marquardt algorithm as training function. The results of one and two wire probe of hot wire anemometry in form instantaneous voltages with coincidence them with average velocity values and change to velocity vectors were used as input data for training of neural network. The network was training in one and two conditions and the results were compared with experimental data. The results showed that the network results are as good agreement with accurate results. Also, a model was defined for interpolating and predicting of middle situations.