JOURNAL OF FACULTY OF ENGINEERING (UNIVERSITY OF TABRIZ)
Year:2007 | Volume:34 | Issue:3 (48) CIVIL ENGINEERING|Papers Count:8

In many parts of the world, the formations of sinkholes are reported by many researches. In the past few years. several sinkholes have formed in the northern part of Hamedan, between Hamedan and Famenin cities. The geotechnical results evaluation indicates that collapsible sandy soil and Karstic bedrock contribute to the formation of those sinkholes. It is understood that the simultaneous role of those factors significantly affects the size of sinkholes. In the previous researches, the mutual role of solubility of bonding material and the presence of collapsible sandy soil are not taken into account. In the current research with consideration of this point, a series of odometer testing performed. The artificially added sodium sulfate, sodium carbonate, and carbonate calcium made possible to consider the effect of chemical bonding on the behaviour of collapsible sandy soils. It is shown that the collapsible behaviour of sandy soil having calcium carbonate as its bonding material is very sensitive to the pH of soil pore water. It is concluded that in the area susceptible to collapsible behaviour, the presence of soluble bonding may significantly affect the size and development of sinkholes.

This paper makes static studies of multiple crack interaction in infinite, elastic, two dimensional bodies applying the Boundary element method. To avoid numerical inaccuracies in crack boundaries the method of Dual boundary element (DBEM) is used here so hyper singular equations are added to the system and this will affect the process of choosing element types. The results in terms of stress intensity factors (SIFs) are presented for a variety of crack arrangements, relative sizes of cracks spacing and crack orientations. In order to calculate the so called factors, crack opening displacement method is used. It is found that crack arrangements have significant effects on SIFs.

Understanding of real behavior of railway bridges is possible by analyzing of Train-Bridge mechanical system. Nevertheless, since the system is excited under the effect of hunting motion of train and is forced to vibrate, it is necessary to model the bridge, the train and the wheel-rail interaction and to obtain system equilibrium equations. While in this paper, modeling and formulation of equilibrium equations have been presented, a computer program has also been developed to solve the problem. Time-history of passing trains over the bridge has been simulated by the computer program. A case study has been carried out on a special bridge and the dynamic responses and its distributions against various speeds of the train have been calculated. The validity of the computer program has been already confirmed by comparing the results of field measurements and the calculations. This paper has particularly focused on 3-D issues of pair-trains with the speed of 100~300km/h over double track bridges.

In order to obtain the isovel contours in a channel cross section, a simple model is proposed. The model is able to estimate the isovel contours in a channel cross section with uniform and composite roughnesses. In this model, it is assumed that each element of boundary influences the velocity at an arbitrary point of the channel cross section in the same way as a velocity distribution profile such as power law does. By integration of the total effect of channel boundary, using the power law velocity distribution, the isovel contours can be easily obtained. Then, by the use of a single point of velocity measurement, discharge can be estimated. The results of discharge estimations show a good agreement between the calculated discharges using the proposed model and experimental ones.

In this paper, the standard deviation of the spheroid up to degree and order 20 in Iran, when using various satellite-derived geopotential models, has been studied. For the comparison, the standard deviations of potential coefficients in various geopotential models are examined. According to the results, the ElGEM-GL04C geopotential model up to degree and order 20 showed small standard deviation over the territory of Iran.

The evaluation of stability and deformation of rock fill dams during the first stage of impounding is a very important subject. The upstream zone of rock fill dams usually is compacted in a dry condition. In the first filling of reservoir, due to the presence of water, a reduction in strength among rock particles and a breakage in contact zone of them happen. This causes sliding between granular materials. Even though there are not enough researches focusing on the saturated collapse or settlement of this phenomenon, the results of monitoring process in several dams indicate the necessity for inclusion of this phenomenon in numerical analysis. This paper provides a numerical analysis to simulate such a collapsible performance. An elasto-plastic constitutive model with the mechanism of strain softening was used with application of Flac 2D Ver. 4.00 as a computational code. For validation of outcoming results, the monitoring information of Masjed Soleyman dam was used. The results show that the implemented model has an acceptable ability to model the behaviour of this dam during the first impounding stage.

One of the factors that affects the flexibility of floor slabs, is the ratio of floor mass to the shear wall mass in shear walled buildings. This ratio may sometimes be one of the most important parameters in floor behavior. To evaluate the importance of this ratio, several structures with different mass ratios have been analyzed in this paper. The results of these analyses have shown that the floor behavior may be quite different if the mass ratio not to be considered, which is the most common rule of ordinary analysis.

An approach of detecting surface deformation based on the use of GPS multipath signals is presented in this paper. The approach has the advantage that one antenna can be used to monitor multiple points or the entire surface and is hence much more cost effective.The general GPS multipath effect will be discussed first, and then the basic principle of computing surface deformations using multipath signals will be introduced.