AMIRKABIR JOURNAL OF CIVIL ENGINEERING (AMIRKABIR)
Year:2011 | Volume:43 | Issue:1|Papers Count:11

This article investigates the performance of Aitken accelerator in analysis by one-dimensional generalized subspace method. At first, it has dealt with non-linear dynamic analysis by generalized subspace technique and the necessity of extending analysis by this method. There after one-dimensional subspace procedure is presented. According to requirement of the process to iteration in each time step, the approach is modified with the help of Aitken accelerator. Finally, the numerical examples, according to modified algorithm, are presented.

Regarding the importance of the supply management for existing transportation facilities and allocating these resources in the rail transportation, travel demand forecasting has a very important role. In this paper the time series models are used to forecast passenger demand in Iranian railway network.Before estimation, model selection and forecasting, the stationary and non-stationary time series models of railway passenger demand are analyzed with the tests of unit root and seasonal unit root. In the modeling part the Box-Jenkins method are used that the main reason for using them was the strong correlation between the data in several months and seasons and repeating exact trends in the fixed basis of time. The Mean Absolute Percentage Error (MAPE) and Root Mean Square Error (RMSE) criteria are used in order to evaluate the performance of models. The final fitted models are in conformity with family of seasonally ARIMA, and have at least 92 percent accuracy in the forecasting.

Porous bituminous mixes that are saturated in cement slurries are named “combi-layer”. These types of mixes consist of coarse aggregates and contains little fines and have a high air voids content (of up to 20%). The porous property of combi-layer makes these mixes to be flexible while the saturated cement slurry improves their resistance to deformation and rutting. This research mechanical properties of one type of porous mix saturated with cement slurry at different cement concentration were investigated. Marshall, Creep and Indirect Tensile Tests were conducted on day and saturated samples. The ITS tests were performed at (-10, zero, 40oC). The results showed that samples saturated at 32% cement had both high strength and appropriate flexibility. Hence with this type of mixes it would be possible to have the benefits of porous mixes (i.e. drainages, skid resistance …) while these mixes have enough strength to resist deformation.

In this project, swelling strain and stress caused by tunnel excavation is determined. Two main parts of the performed analysis is mentioned here. First, swelling differential equation is solved by analytical method and the swelling quantities related to tunnel environment is calculated. Then in the second part, the amount of stresses of the tunnel environment caused by tunnel excavation is evaluated. Calculations of this part are processed by a finite element method that use isoperimetric element to model the tunnel. MATLAB code is used to process numerical model of the second part.

In general, shear wall design is based on flexural ductility. In this design approach, behavior of the shear walls is more similar to a cantilever beam with significant bending moment at its base. In such systems, the main input energy dissipation during seismic events happens at the base of the shear wall. In this paper, in order to improve the behavior of these important lateral resisting mechanism in structural systems, the possibility of dual type behavior (flexural and shear) were investigated. At first, the potential of this approach in improving the behavior of shear walls has been examined in a simplified structural model. Later, three types of shear walls including slit walls, shear walls with opening and frame-wall systems have been studied. The results show the capability of dual ductility modes of behavior in all three systems. Energy dissipation dispersion in these systems is better than the ordinary shear walls. Among the dual ductility systems, the frame-wall system has shown a superior performance compared with that of the two other systems.

In this research, using the finite volume method of Roe-TVD, supercritical flow in the curved channel of Reinauer and Hager was studied and the results were compared with the analytical method of Knapp-Ippen, the numerical method of HLL and the available experimental data of Reinauer and Hager. Then, using the numerical results, the accuracy of the assumptions of the analytical method was evaluated. It was observed that the super-critical oblique standing waves are diffused along the bend way. With an inlet Froude number, Fr0<4.2, the assumptions of constant average cross-sectional velocity along the bend and frictionless flow or constant specific energy is acceptable with an error of around one percent and the velocity variation at the external wall is tolerable with a maximum error of four percent. By increasing the inlet Froude number, flow at the internal wall dries up and the above assumptions are invalidated.

Braced frames have been known as frequently used earthquake resistant systems. If a limited length of a member in such a bracing system can undergo ductile behavior, the structure would sustain in a reliable performance, dissipating a large amount of seismic energy during earthquake. Knee Braced Frames, KBFs, are among the ductile systems having such mechanisms. In this paper, single-story single-bay steel Diagonal and Chevron Knee Braced Frames (DKBF & CKBF) with different configurations have been modeled using ANSYS software and their lateral behavior have been studied and compared. Comparing the hysteretic curves and ductility factors, better performance of CKBF compared with DKBF has been found due to its more knee elements and thus having higher damping. In two similar frame configurations, CKBF1 reaches to 25 mm displacement while DKBF2 displacement limits to 15 mm, such that following the same loading protocol, ductility factor of CKBF1 is 60% more than that of DKBF2.Comparing VonMises and shear stress contours for knee elements, shows the fact that the more symmetric the KBF, the more efficient the knee element in dissipating energy leading to using the whole section capacity.

3D spatial data acquired using photogrammetric techniques, is one of the most accurate and economic spatial data sources for GIS and spatial analysis. But, there are still many problems about storing, structuring, and appropriate management of spatial data obtained using photogrammetric techniques. According to the abilities of spatial database management systems, it can be said that on-line integration of photogrammetric and spatial database management systems, saves time and cost of producing, structuring and updating map products. Also, by means of theses integrated systems that produce structured data based on defined standards and topological relations between features in real world at the time of feature digitizing process, a great development in the field of reel-time and on-line GIS can be occurred. In this paper, in addition to the evaluation of necessity and importance of integration of photogrammetric and spatial database management systems, and explaining different levels of the integration, design, implementation, and test of an integrated system is discussed.

Various methods have been used to create continuous surfaces from sampled data. One of the most common geostatistical methods is Kriging, which provides an accurate estimation based on existing spatial structure in the sample points. However, Kriging method is sensitive to the errors in the input data, the dispersion of the sample. The purpose of this research is to develop a new method to handle the uncertainties resulted from the input data in the Kriging method. In this approach, the existing uncertainties in the input data are modeled by fuzzy computations, and the variogram variables are calculated in fuzzy mode. To test the new hybrid method, the sodium contamination values in Zanjan aquifer are used. The results show a generally improved accuracy in comparison to the ordinary Kriging method. Consideration of all equations and values in fuzzy raises the complexity of the computation. On the other hand, the integrity problems associated other researches on fuzzy kriging are resolved.

The MIP technique in combination with Piecewise linear function has lead to a method of stope design, which uses a one, two or three-dimensional discretisation of the ore zone (block model). An optimal economic stoping boundary is developed by optimizing the starting and ending locations for mining within each row or column of blocks (a mining panel). To determine these locations, two piecewise linear, cumulative functions are used for each row. The stope boundary model is optimized using a MIP approach that employs a special kind of variables named “special ordered sets type 2”. This paper presents a step by step explanation of the model construction. The optimizing problem is solved using the MIP approach. GAMS/Cplex11 software tool is employed to numerical examples. The model is validated by comparison with similar cases.

In rock engineering practice, understanding the most effective parameters and their relationships is important in order to obtain an optimum engineering design. The applications of rock engineering system (RES) in the analysis of complicated rock engineering processes have been widespread. In this method, the main parameters are located along the diagonal of the matrix, and their interactions are quantified by assigning values in the off-diagonal elements. Then, this matrix is used to assess the amount of cause and effect of each parameter within the whole system. In this paper, a rock engineering systems is constructed where the coding of the matrix is made using fuzzy mathematics. This system is used to analyze the stability of the water transmit tunnel of Seymareh Dam within the crushed zone of Graben rocks. The results are compared to those of the rock mass classification systems. It is observed that the bedding and falts are the two major factors of instability. Using the new method, the Graben rock is classified in group III, i.e. moderately stable rock, which is close to what predicted using rock classification system.