JOURNAL OF CIVIL ENGINEERING ISLAMIC AZAD UNIVERSITY
Year:2008 | Volume:1 | Issue:2|Papers Count:8

It has been more than a decade since mesh-free methods gained considerable attention in engineering and science. The main distinction of the methods with respect to the FEM is their shape functions. In this regard, Diffuse Element Method (DEM) employs Least-Squares (LS) approximation, while Element-Free Galerkin Method (EFGM) benefits from Moving-Least-Squares (MLS) approximation for shape function construction. In order to compare the results of the methods, Boussinesq problem, which has closed-form solution, is used as a benchmark. The results are compared in displacement and stress fields. Finally, it is concluded that EFGM error is less than DEM in the both fields. This is more pronounced in stress field due to weight function being constant in DEM.

During the recent years, the seismic nonlinear behavior of concrete gravity dams was in the center of consideration of dam engineers. Numerous researches have been conducted in order to determine how the dams behave against the seismic loads. Many achievements were obtained in the process of nonlinear analysis and design of concrete dams. In this paper, we study the nonlinear behavior of dam-reservoir-foundation interaction during an earthquake. Using the finite element method and smeared crack approach, some different seismic nonlinear analyses were done to study the impact of the foundation mass and flexibility on the seismic behavior of the dam. A two-dimensional finite element model of a concrete gravity dam including the dam body, a part of its foundation and a part of the reservoir was made. Staggered displacement method was used for the purpose of solving coupled equations. In addition, the proper boundary conditions were used in both reservoir and foundation in order to absorb the energy of waves at the far end boundaries. The results show that both the foundation mass and flexibility have an outstanding impact on the nonlinear behavior of dams and therefore it is necessary to consider the foundation effect while analyzing concrete dams.

Using a two dimensional flume with 12 m length, 25 cm wide and 75 cm height, and constant head tank, continuous density current under clean water, was developed and studied. Kaolin particles with 20-micron mean diameter were used for density differences. This set up was used to study developed velocity profile, drag forces and relation between mean and maximum velocity. Instantaneous velocity was measured using Acoustic Doppler Velocimeter (ADV). The results show, it is possible to present non-dimensional velocities as similarity profile. Also velocity profile and mean velocity help us to determined friction coefficient for 2-D turbidity currents and their changes with respect to Reynolds number.

Cavitation is the most important problem in bottom outlets in dams due to high velocity. Designers are used the proper aeration system for diminishing of cavitation. Sefidrood dam in the north of Iran has been subjected to cavitation in its bottom outlets since many years ago due to high flow velocity up to 30 m/s. In present work, the computational fluid dynamics (CFD) through the finite volume method (FVM) was used for numerical simulation of flow in these conduits. The VOF model in Fluent software was used for computation of equations. This simulation carried out in 3-D and two-phase flow includes air and water. Also, the model of was used for turbulent of flow. For avoiding of cavitation, suitable aeration system includes bottom ramp, sidewall ramp, and air duct was used. Flow characteristics such as flow profile, velocity, and pressure were computed, and then cavitation index was determined. The accuracy of model will be established through the comparison of results with available experimental data of hydraulic model of the bottom outlets of Sefidrood dam in Water Research Center of Tehran.

From standpoint of sustainable water resources management, the main objective of a development plan is to utilize water in the most efficient and affordable prices. This requires implementing the efficient utilization of water in such a way to yield a better balance between supply and demand. Karoon and Dez river watersheds with their strategic energy and water resources potential and their unique characteristics offer unique challenges for water planners and decision makers. In this paper, the WEAP (Water Evaluation and Planning System) model has used to simulate the long-term records of water supply and demand. Different scenarios of Water Demand Management (WDM) that can be included are improvement of irrigation efficiency, definition of optimum crop pattern, loss reduction of agricultural products and educational activities. The above management schemes evaluated with an economic approach. The result show that if no attention is paid to WDM, all of the water demand are not attainable in developed stages, But with adapting these schemes better water quality conditions and higher development targets could be attained.

It has been widespread to use masonry and mud-brick materials in implementation of buildings in Iran since previous centuries. So far, in most of cities and most of rural regions, warm and dry regions, the masonry and mud-brick buildings include major part of the superstructures of such regions. Because of vulnerability of these buildings against previous earthquakes and being located most of villages in area prone to having earthquakes, it is obviously important to study the behavior and operation of this type of buildings against earthquake. In the present article, the methods of surveying on vulnerability of such existing structures in Iran and modality of reinforcement and optimization of them are discussed.

It is quite postulated that the seismic characteristics of acceleration time history recorded at stations near epicenter differ, considerably, from those of far stations either in frequency contents or PGA. This difference has not been considered in Iranian Standard No. 2800. Therefore, the necessity of more research work seems to be of importance. The objectives of this paper are the comparison and assessment of performance of reinforced concrete structures with MRF system built on soils type II subjected to near source as well as far source site specific response spectra obtained from a Probabilistic Seismic Hazard Analysis (PSHA). Calculation of the performance point (PP) of moment resisting R/C structures having 2, 4, 6 and 10 stories and comparing their structural responses such as drift with those of Iranian Standard No. 2800 is another goal of this study. It is notable that the directivity effect, as an important factor in the near source problems, is considered. The effects of such important factors on structural responses of special R/C structures (SMRF) are demonstrated and discussed by analyzing four types of R/C structures subjected to near source acceleration (Bam station) and far source acceleration (Darmazar station). The compatibility of selected accelerations with estimated site response spectra as well as those of Standard No. 2800 obtained from near and far sources is studied and assessed as the results of this research work.

The present study was conducted with the aim to forecast irrigation demand in city of Borujerd . The main purpose includes considering the effects of economic variables on decision making process for irrigation water allocation to cultivated areas. The Expected Utility Model was applied for exerting economic variables. The cultivated area function was estimated in an econometric model upon considering economic variables. In this study by forecasting cultivated areas through the last two years of period under study using estimated function, and also knowing amount of water required for related crops, irrigation demand was determined. Main Findings reveal that amount of predicated annual water demand for wheat during years 2004 and 2005 were 188100 and 216600 m3 and for sugarbeet at the same years, 420670 and 327980 m3, respectively. However, actual amount of annual water demand at the same years were 119700 and 142500 m3 for wheat and 313720 and 406410 m3 for sugarbeet, respectively.