Journal of the Structural Engineering and Geotechnics
Volume:3 Issue: 2, Spring 2013

Estimation of the nonlinear buckling capacity of thin walled shells is one of the most important aspects of structural mechanics. In this study the axial buckling load of 132 stiffened shells were numerically calculated. The applicability of artificial neural networks (ANN) in predicting the buckling capacity of vertically stiffened shells was studied. To this end feed forward (FF) multi-layer perceptron (MLP) neural networks were used. The shell height (H), shell diameter (D), shell thickness (t), width (b), thickness of stiffeners (ts), and unstiffened length of the cylinder (l) were considered as the input vector; the relative buckling capacities of stiffened shells to unstiffened ones (Pcr/Pcr0) were considered as the output of the MLP networks. The back propagation algorithm was used to train the networks. Different structures of ANN were trained by 100 of the outputs of the numerical analysis and tested by 32 remains. The best ANN structure was selected based on the mean square error (MSE) and correlation coefficient (R2). The results of this study revealed that MLP neural networks can remarkably predict the axial capacity of stiffened shells. A parametric study on the buckling loads of the stiffened shells was performed by using the neural prediction and FEM.

The quick growth of the population and the increasing need of the demands for developing caused the construction and production process formed with increasing technology than the past, this speeding in construction process caused the construction quality and executing engineering points and the lack of accommodation of construction to the plans increase more. So the purpose of this article is the definition and arrangement of control checklist and planning basic criterions and indices which are very important in an agent construction management system. According to the fact that checklist controlling are conducted in Qazvin city in field studies and the checklists have been arranged qualitatively, so for determining the amount of plan accommodation and the construction, the hierarchical analysis method AHP is used. And the checklists options have been used as modeling indices and finally according to the results of modeling this result is derived that in most of the cases the indices are accommodating with the plans but in some cases these principles became observable significant.

When categorizing water management alternatives, to meet water needs, water transfer is seen as an option that tends to supply more water. Most developing countries where limited water resources are available with high spatiotemporal dispersion, favor this option. The numbers of such projects that have been proposed, implemented, and operated in recent years evidence the desirability of this alternative. World experiences of inter-basin water transfer however prove that having holistic, systemic view, along with taking into account the principles of sustainable development as well as lifetime cost-income balance are required for such projects to be implemented. This paper intends to put emphasis on the fact that when water transfer projects are being examined, the principle of transparency and public acceptance should be recognized. In doing so, the world experiences and criteria are demonstrated and Beheshtabad project is briefly described. Moreover, it argues that it is not logical to regard the long term average yield as a basis for estimating the water availability at the source basin. The benefits of the project should be fairly distributed between source and destination basins and it is required to thoroughly investigate the other alternatives along with water transfer option.

In this paper, the mechanical behavior of plastic concrete being used in the cut-off walls of earth dams has been studied. To do the task, triaxial compression tests on the specimens in various ages and mix designs under different confining pressures have been done and the stress-strain behavior of such materials and their strength parameter changes has been experimentally investigated. It has been observed that increasing the confining pressures applied on the specimens causes the material behavior to be alike the more ductile materials and the compressive strength increases considerably as well. Moreover, a parametric study has been carried out to investigate the influence of essential parameters affecting the shear strength parameters of these materials. According to the research, increasing the coarse to fine aggregates ratio leads to the increase of compressive strength of the specimens as well as the increase of the cohesion and internal friction angle of the materials. Furthermore, the bentonite content decrease and the cement factor increase results in an increase of the cohesion parameter of plastic concretes and decrease of the internal friction angle of such materials.

In order to obtain the soil water retention curve of an unsaturated soil which is defined as the relationship between water content and suction, extensive laboratory tests are essential. These laboratory tests are usually costly and time consuming. Moreover, for most practical problems, it has been found that approximate unsaturated soil properties are adequate for analysis. Thus, empirical procedures to predict unsaturated soil parameters would be invaluable. The water retention curve can be measured or predicted based on soil index properties. Estimation based on index properties is highly desirable due to its simplicity and low cost.
In this paper, the constant parameters of well-known Van-Genuchten and Fredlund-Xing equations based on index properties of fine soils are derived. The comparisons show that the curves predicted by these models are in a good agreement with the experimental results.

In many cases of heavy earthquakes, liquefaction has resulted in serious damages. Existing anisotropy in soil layers results in some difficulties to realize the reason for these phenomena. Loose sand lenses buried in fine soils are one of the cases which may result in these problems and as a weak point during the earthquake can cause this phenomenon. In this paper, using FLAC 2D software, double sand lenses liquefaction mechanism and soil deformation due to applying cyclic loading has been studied and investigated. The FLAC software that has been used for analyzing is capable of modeling progressed models of soil and loading under different conditions.