MODARES TECHNICAL AND ENGINEERING
Year:2007 | Volume:- | Issue:29 (SPECIAL ISSUE ON CIVIL ENGINEERING)|Papers Count:9

The dimensions, cracking and different responses of concrete in tension and compression in deep beams causes nonlinear behavior. Therefore, to get better understanding of the behavior of these beams, nonlinear analysis could be useful. In this paper a nonlinear capable computer program (ANSYS) were used to analysis more than 100 deep beams. All the beams were loaded from top mid-center and have different span to depth ratio, reinforcement and dimensions. We compared results with the analytical results of available methods, standards and experimental results. The results indicated that the chosen model yielded accurate results and the use of more than 0.025 bde of main reinforcement does not add to ultimate strength, but also causes early failure (local).

Although seismic behavior of 2D trapezoidal shaped hills depends on their geometry, their constitutive behavior and on the characteristics of the incident waves, yet. The relative importance of these independent parameters has not been clarified. This paper presents the results of an extensive parametric study on seismic responses of 2D trapezoidal shaped hills, subjected to vertically propagating incident P- and SV- waves, considering various cases of shape ratio, flank's angle, Poisson ratio and incident wave's length. Clear perspectives of the induced scattering pattern are given by investigation of time-domain responses. Clear perspectives of how the above mentioned parameters could control the amplification pattern are also given by investigation of frequency-domain responses. Simple formula and tables have been proposed for estimating the characteristic site period and the average amplification potential of trapezoidal shaped hills, which could be easily applied in site effect microzonation studies of topographic areas.

Buildings in Iran are usually designed without considering the effects of infilled frames on seismic behavior. As it was seen in the past earthquakes, existence of infilled frames results in more stiffened buildings and therefore they show different responses to ground excitation. The iranian code for seismic resistant design recommends decreasing just 20% of the fundamental period of buildings. Obviously, based on number and type of infilled frames and their configuration, this recommendation cannot apply to all cases. In this paper, after investigating the recommendation of Iranian code for seismic resistant design of buildings with infilled frames, the seismic behavior of two types of reinforced concrete buildings designed on the basis of Iranian code has been evaluated. Using nonlinear static and dynamic analyses, with modeling of infilled frames, the seismic behavior of buildings with and without infilled frames have been evaluated and compared. Results show that the influence of masonry infilled frames on seismic behavior of reinforced concrete buildings is not negligible, and based on configuration of infilled frames, the type and stiffness of infilled panels, some points must be considered in analysis and design.

The main objective of this research is to investigate factors governing the dispersivity behaviour of montmorillonite due to the pore fluid characteristics, mainly pH variations. To achieve this objective, a series of bentonite samples were laboratory dispersed by the application of sodium sulfate and sodium hydroxide. A bentonite sample was used in this study in which its main fraction was montmorillonite. Then, the pH of samples was changed by the use of sulfuric acid. Following this preparation process, with the performance of a series of physical experiments and micro-structural evaluation, the behaviour of soil samples were investigated.The results of this study indicate that in the presence of low concentration of sodium cations, the potential of dispersivity increases. Then with a further increase in sodium concentration, the soil structure changes from dispersive structure to a more flocculated structure. On the other hand, at the sample with maximum dispersive structure and specific concentration of sodium cation, the increase on the concentration of hydrogen ion causes a decrease on the dispersivity performance of soil. The behaviour is a function of pH and anion type of electrolyte. SEM pictures approve the changes on the soil structure due to the changes on the pore fluid characteristics. In addition, a decrease on the peak location of the major basal spacing of bentonite in XRD analysis after the application of acid also confirms the decrease of the dispersivity behaviour of soil.

Two dimensional seepage analysis is vastly used for modeling dams constructed in U-shaped valleys. However, for dams on V-shaped valleys, three dimensional analysis would be more appropriate. Therefore, valley shape is considered as a key factor in selection of type of analysis. In this paper, many hypothetical embankment dams with different valley shapes were investigated. Two and three dimensional finite element seepage analyses under steady state conditions were performed and differences in the position of phreatic line, hydraulic gradient, and velocity distribution in these analyses and the effect of valley shape on the differences were investigated. Results showed that when the angle between the valley side and horizon is from 53 to 73 degrees, valley shape has the greatest effect on seepage analysis (up to 23%). On the other hand, when the ratio of bottom width to the height of valley exceeds 0.75, effects of valley shape on seepage analysis are negligible.

The overall mandate of this study is to calculate Tehran's air pollution due to mobile sources. Mobile sources have been categorized into three category (i) light duty vehicles (passenger cars and tracks), (ii) heavy duty vehicles (bus, mini bus, heavy diesel tracks), and (iii) motorcycles (four stroke, two stroke, and moped). The first step to achieve the goal is to use the best-developed model, make traffic and emissions information updated. Mobile sources population, their mileage, and emission factors have been updated in this study. Using the updated information has run the selected model. Mobile sources have contribution of 88.1 percent in Tehran's air pollution in 2002 with motorcycles, light duty vehicles and heavy duty vehicles have a contribution of 22, 74, and 3 percent respectively among mobile sources.

In this work, a number of horizontally perforated clay blocks have been designed and thermal performances of each ones have been evaluated by numerical calculations. The design process has been achieved with the collaboration of manufacturers, taking into consideration technical and normative restrictions. Afterwards, parametric numerical studies have been undertaken for determination of effect of variations in the geometry of the block, and the thermal properties of the materials. Results make clear that expectations related to the thermal performance for external envelope walls, in the Iranian building code, can be reached by some of these new generation clays blocks.

Prediction of the scour around a group of pile in the field exposed to oscillatory waves is very important for many offshore structure and coastal engineering projects. Conventional predictive formulas for geometric properties of scour hole, however, are not able to provide sufficiently accurate results. Artificial Neural Networks (ANNs) are simplified mathematical representation of human brain. Three-layer normal feed-forward ANNs are powerful tools for input-output mapping and have been widely used in civil engineering problems In this article the ANNs approach is used to predict the geometric properties of the scour around a pile group using dimensionless groups of individual parameters, namely, Reynolds number, Keulegan and Carpenter number, Shields parameter, and Sediment number.Two different ANNs including multilayer perceptron (with four different learning rules) and radial basis functions neural networks are used for this purpose. The results show that a three-layer normal feed-forward multilayer perceptron with quick propagation (QP) learning rule can predict the scour hole properties successfully.