Showing 6 results for Structures
A. Keshavarzi and M. J. Kazemzadeh Parsee,
Volume 24, Issue 1 (7-2005)
Abstract
Flow separation at water intake is the main cause of head loss and flow discharge reduction.
As a result, study of shape and size of separation is very essential when designing an optimum water intake. Water intake is normally built with a 90 degree angle to the main channel flow direction. However, the flow structure in this type of water intake consists of large separation size along with vortex generation. In this study, the effect of the ratio of discharge at water intake to the main channel discharge (Qr) on the location and size of separation is investigated numerically and experimentally. The velocity of the flow at each point is measured in two dimensions using electromagnetic velocity meter. The results from the experimental data indicate that the location and shape of separations are a function of flow discharge ratio (Qr). These results also indicate that at higher ratios of flow discharge, the separation occurs downstream the water intake, whereas at lower flow discharges, the flow separation occurs upstream the water intake. Additionally, the capabilites of numerical turbulence computation models including standard k-e and RNG k-e models are investigated in this study. The computed flow velocity from the turbulence models showed that the result of standard k-e model is approximately close to the experimental data when compared with RNG k-e model
S. M. Zahrai and B. Rad,
Volume 25, Issue 2 (1-2007)
Abstract
In recent years, destructive earthquakes have shown the deficiencies of the existing buildings. One of the most effective mechanisms for dissipating the earthquake energy is inelastic deformation of the steel components. The objective of this research is to study the application of metallic dampers for dissipation of the earthquake energy and to investigate the behavior of concrete structures incorporating these dampers. Therefore, the metallic dampers and the behavior of concrete structures having these dampers are studied first. Afterwards, a typical metallic damper is used in four different types of concrete structure. The required dampers are designed and nonlinear earthquake analysis is applied to investigate the behavior of the structures. Finally, the buildings are subjected to various earthquakes to generalize the results. The results show that the incorporation of the metallic dampers significantly decreases the relative and absolute drift, the structure and the stories damage indices and, finally, the number of plastic hinges. Furthermore, the hysteretic energy dissipation demand also decreases in structural components. Despite the reduction in the inner forces of structural components, story shear forces slightly increase due to increase of lateral stiffness, but much of these forces will concentrate in dampers. Moreover, the combination of moment resisting frame, shear wall, and metallic dampers are studied. The results show a similar trend in the stated parameters- especially the drift and the hysteresis energy dissipation demand.
H. Moharrami, M.t. Shahrabi Farahani and H. Shourabi,
Volume 26, Issue 1 (7-2007)
Abstract
Marine structures are one of the most important and susceptible facilities in Iran due to corrosion. The two methods of Cathodic Protection, namely, the cathodic protection with sacrificial anodes and cathodic protection using impressed current, are widely used for corrosion protection. According to the former, sacrificial anodes are installed at several points in the structure. Position of the anodes for achieving the required protection is a problem that engineers are very much interested in, and only empirical methods have so far been used to determine these positions. Empirical rules, however, might cause either overprotection or underprotection. A major goal of this research is to develop a systematic way for analysis and automated design of Cathodic Protection systems that not only deliver almost uniformly protected structures but also minimize the costs. To this end, a Genetic Algorithm (GA) routine is used to determine the optimal position of anodes on the structure such that a uniformly protected design with minimum cost is achieved. The percentage of protection in each design has been taken as its fitness criterion. To figure out the situation of corrosion protection on the structure, the entire offshore structure with its complex system at anodes and surrounding electrolyte is modeled and analyzed by a finite element algorithm. Employing GA gradually modifies the generation of designs. The design which completely protects the structure and whose cost is minimum is introduced as the optimum design. To show the capability of the proposed method in achieving the optimum design, two examples are offshore presented.
K. Abedi, M.r. Sheidaii,
Volume 26, Issue 1 (7-2007)
Abstract
Considering the vulnerability of double-layer grid space structures to progressive collapse phenomenon, it is necessary to pay special attention to this phenomenon in the design process. Alternate path method is one of the most appropriate and accepted methods for progressive collapse resistant design of structures. Alternate Path Method permits local failure to occur but provides alternate paths around the damaged area so that the structure is able to absorb the applied loads without overall collapse. Following the sudden initial local failure event, severe dynamic effects may arise which should be taken into account in determining the realistic collapse behavior of the structure. In this paper, a new methodology based on alternate path method is presented to apply dynamic effects of initial local failure. The method is called nonlinear dynamic alternate path method. Due to its capability to take account of dynamic nature of the failure, this method can be used to evaluate realistic collapse behavior of the structure and to investigate the vulnerability of the structure to progressive collapse phenomenon.
A. Bahari, M. Roodbari Shahmiri , N. Mirnia,
Volume 31, Issue 1 (6-2012)
Abstract
Recently, high – K materials such as Al2O3 and TiO2 films have been studied to replace ultra thin gate silicon dioxide film. In the present work, these films were grown on the top of Si(100) surface at different temperatures and under ultra high vacuum conditions. The obtained results showed that Al2O3 has a structure better than that of TiO2 and thus can be used as a good gate dielectric for future MISFET (Metal – Insulator- Semiconductor- Field – Effect- Transistors) devices.
D. Haghshenas, A. Amirjani,
Volume 36, Issue 4 (3-2018)
Abstract
In this study, null and one-dimensional nanoparticles and nanostructures of Ag and Ag-Cu were synthesized using polyol method. In order to prepare different nanostructures with the same synthesis route, thermodynamics and kinetic conditions of the system were manipulated. In the thermodynamics approach, the nanostructures with the minimum surface energy were obtained as the final product, while in kinetic approach, the nanostructures with the lower activation energy were formed. By using these appraoches, Ag and Ag-Cu spherical and cubical nanostructures were produced in the size range of 90-100 nm. Also, by manipulating the kinetic conditions of the system, silver nanowires with the diameters in the range of 100-200 nm and the length of several microns were obtained successfully. The effect of Cu ions (Cu2+) on aspect ratio of the synthesized silver nanowires by polyol method was evaluated.
