نشریه مهندسی عمران و محیط زیست دانشگاه تبریز
سال چهل و دوم شماره 3 (پیاپی 68، پاییز 1391)

Concrete is currently the most widely used construction material in the world. However, its mechanical properties when suffering damages have not been fully understood which may be the reason that no generally accepted nonlinear theory had been available for the analysis and design of concrete structures. In fact, the complexity of concrete material originated from two essential characteristics, that is, nonlinearity and randomness. In the past 25 years, there have been significant developments in the production and use of high strength concrete HSC. During this period, experimental research related to the behavior of high strength concrete members has increased significantly. However, with the availability of data on higher strength concretes, the applicability of the code equations need to be reevaluated and the extrapolation of equation from lower strength to high-strength concretes needs more experimental verification. The experimental data on HSC columns still remains limited and the applicability of code equations to members mad of HSC needs more experimental verification. The ductility of reinforced concrete columns is an important factor for the strength and stability of reinforced concrete structures. The ductility of columns can be achieved by the confinement of the core concrete. Recently, concrete strengths much higher than 60 MPa have been used in the construction industry. However, the behavior of high strength concrete columns is not adequately known, yet. As a result, the design provisions of current building codes related to strength and ductility of high strength concrete columns cannot be not satisfactory. This paper presents the results of a research project in which the available test data on high strength concrete columns have been evaluated in terms of strength, ductility, and drift ratios. The relationships between confinement parameters and column performance are illustrated. A number of different formulas have been proposed for predicting the strength and ductility of high-strength concrete columns by various researchers. In the present study, models and experimental results collected from the literature are evaluated. The investigations show that the uncertainties of effective factors on strength and ductility of such columns must be considered. A probabilistic analysis is needed to evaluate the uncertainty in the design process. In this paper, the mechanical properties of steel and concrete are supposed that to be uncertain and have normal and lognormal distributions with different coefficient of variations, changing from 10% to 25%. The Monte Carlo method is used to generate random variables. The strength and ductility parameters for generated variables are calculated and compared with the experimental data. By using the results, the reliability and the safety level of the formulas are determined. It is shown that the proposed model by the authors has a very good agreement with experimental results with minimum errors and sufficient reliability as well.

Scour around bridge pier is one of the most influential and important factors in the destruction of bridges. This phone man occurs due to contact and separate lines of flow of pier and complex vortex flows. Because it depends on many influential variables, determination of influential variables and formulation of mathematical models is difficult. Conventionally, the multiple linear regression procedure has been known as the most popular model in simulating the bridge pier scour. However, when the nonlinear phenomenon is significant, the multiple linear will fail to develop an appropriate predictive model. Recently, Data Mining and Meta Model approaches such as artificial neural network (ANN) and neuro-fuzzy methods have been used successfully for the bridge pier scour modeling. In this research, capability of Data Mining and Meta Model is evaluated for simulation of bridge pier scouring using laboratory and field data of cylindrical and square pier and non-cohesive soil. In one hand, using Feed Forward Neural Network, Radial Basis Function, generalized regression neural network, Adaptive Neuro-Fuzzy Inference System and experimental equations, and in other, the dimensional and non-dimensional data, scour is calculated and then using sensitivity analysis, effect of all parameters on pier scouring is determined. The results of simulation indicate that the FFNN has higher coefficient of determination and lower mean absolute relative error compared to RBF, GRNN and ANFIS models. Finally, sensitivity analysis shows that flow velocity has the greatest scour depth with dimensional data, while non-dimensional bed shear stress has the biggest influence on dimensionless data. A conclusion is reached that the Data Mining and Meta modeling approach is suitable for modeling of bridge pier scour.

Sediment tanks are mainly designed to eliminate the excess of sediments which can be transported through the irrigation channels, or diverted river channels and channels leading to water power turbines. These structures are also implemented in the water treatment plants of the first and second types where most of the carried out investigations have been focused on. A large number of researches have been undertaken on the performance of the settling tanks under the effects of density current flow, gravity as well as the concentration of the fluid and their effects on the flow patterns and density in sediment tanks. In the present research, the existence of hydrodynamic process in sediment tanks by the use of Finite Volume Method (FVM) with the aid of large eddy simulation (LES) and Lagrangian movement of the sediment particles has been analyzed. After modeling the flow and obtaining their pattern, analysis on the way of the particle movements in sediment tank and trap efficiency are presented and accordingly, granular distribution of particles and concentration of the sediment particles, on the bed as well as at the outlet section are obtained. Using this model, it is revealed that in sediment tanks with the mentioned circumstances, almost all of the particles with larger diameters than 850m are trapped.

Nowadays, rapid growth of cities and other factors like climate change motivate to apply adaptive water resource management. In this paper, the case of Tabriz urban water is studied. Tabriz, one of the large cities of Iran, needs a reliable water supply. Two transfer lines from Zarrinehroud and Nahand reservoirs and groundwater are the main resources for the city. The leak detection and network rehabilitation is also assumed as a potential water supply resource. In this research, water supplying for the city is studied up to the year 2023 considering population growth and change in consumption pattern. Three conflicting objectives are considered as minimizing the cost of water supply, minimizing the environmental externalities, and maximizing the water supply per capita. In the first function, the cost of supplying one cubic meter is the sum of the multiplication of the amount of water from the groundwater, surface waters and leak detection. In environmental objective, the problem of Urmia Lake is considered. This important ecosystem is now drying because of various factors among them water diversion from recharging rivers. Then water transfers to city should be reduced. In the case of third objective, the social attitude on having sufficient water for now and next generations is considered. Then three main objectives of integrated water resources management are considered in this approach. To aggregate the three different objectives, the compromise programming approach is used. In this method, firstly the inputs are normalized. Then they are weighted based on the importance of the objectives and finally they are scaled based on their amounts. If the risk is important for the decision maker larger, values get more importance and smaller values find less magnitude. This approach has found high attention in multi objective optimization especially in water resources management. Reliability is proposed as a system performance measure and then it is evaluated as a performance function. Improved Particle Swarm Optimization is used for solving the model and its performance is then compared with the basic PSO. Outcomes show that adding the mutation operator to the basic algorithm has improved its performance. Existing resources will be enough just up to 2021, according to the system reliability level and after this year new resources will be needed. In addition, the sensitivity of system to the failure of water supply resources is analyzed, showing high sensitivity for transfers from Zarrinehroud. As suggestions for further studies, the improved PSO approach could be compared with other evolutionary multi objective methods like genetic algorithms. In addition, rather than obtaining aggregated multi objective, the Pareto frontier may be attained which provides a space in which trade off among the objectives is visible. This helps the decision maker to select more preferred option. It is desired for selecting better actions which is urgently needed for robust water management. In addition, using stochastic simulation on the system to find the reliability of water resources in this city is under study.

In recent years, many efforts have been made in the field of development of water quality models to estimate the amount and rate of pollution of rivers, coasts and the estuaries. Many factors are considered in these models. For example, coliforms, BOD, SOD, nitrogen cycle, dissolved oxygen (DO) and phosphorus can be pointed out. The purpose of this research is dynamic investigation of flow and water quality parameters in Karkheh River. According to available data, the parameters of salinity, BOD, and phosphorus for a reach of Karkheh River between Paye Pole and Hamidiyeh stations were analyzed and simulated and Abdelkhan hydrometric station was selected as a survey station. Before proceeding to the modeling of water quality and sediment transport in river systems, it is necessary to solve hydrodynamic equations affecting the river flows. For this purpose, FASTER model has been used. Two time periods between the years 1386-1388 were selected for the model calibration and verification. For solving the hydrodynamics of flow, it is necessary that Manning roughness coefficient (n) to be calibrated in FASTER model. With adjusting of this factor, value of 0.028 was chosen. In the next step Advection Dispersion Equation (ADE) must be solved. For this purpose, 4 Dispersion Coefficients (DL), were used and with trial and error, constant coefficients were determined for the quality parameters. By comparing the measured values and the calculated values by the model in Karkheh River, for the above parameters, the Fischer Dispersion Coefficient was selected by the reasonable and acceptable comparisons. Also run results and calculated errors showed that the model was able to accurately predict hydrodynamic characters and water quality parameters

Behavior of soil during construction of tunnels is one of the important topics studied in the geotechnical engineering that regards to ground settlement and tunnel deformations. During last decades tunneling technology has improved and developed around the world and a lot of tunnels constructed in shallow depth of urban areas for different purposes. Excessive settlement from Tunneling may cause damage to adjacent buildings and overlying facilities. Therefore, the behavior of the soil and interaction between soil and tunnel during tunneling has major significance and should be studied. This research work presents the results of laboratory and numerical investigations on the deformation behavior of tunnel, modeled in sandy soil with incline layers of clay in various levels of surcharge A series of 15 tests are conducted using geotechnical centrifuge apparatus of Geotechnical Research Center at Iran University of Science and Technology and tunnel deformations is investigated in different conditions of incline clay layers. Experimental results show that the placement of inclined clay layers in sandy soil increases the vertical and horizontal deformations of the tunnels about 230 and 140 percent, respectively.

Industrial development and increasing high-elevated construction makes it necessary to increase the bearing capacity of soil in some areas with unsuitable soil. Due to these reasons and environmental restrictions on the public works, ground improvement is becoming a necessary part of the infrastructure development projects, both in the developed and developing countries, in the past decade. The basic principles of ground improvement were unchanged since the beginning of the history of mankind. But the practices are changing with time due to the development of new materials, new machinery, new technologies such as computer, software and sophisticated instrumentation. For example, two Vibroflotation and Vibroreplacement methods are more efficient methods in soil stabilization process. The application of vibroreplacement yields to mechanical properties improvement, so that the foundation soil can fulfill the dered for 2 blocks with 8 floors in the south of Iran (Ahvaz). After drilling 6 boreholes with 40 meter depth requirements relating to loading conditions, bearing, settlement, stability and liquefaction potential. In these methods, main operations of the vibrator during construction of a gravel column are penetration of the vibrator into the soil to the designed depth and compaction of the material from the bottom up towards the surface. In this research, we have briefly investigated these two mentioned methods. Also, a soil stabilization project has been consiin site of the project, geotechnical conditions and other specification of this project completely demonstrated. Designed depth of soil stabilization has been considered 10 meter. improvement criteria for all methods can be finally set only in test fields. The test field establishes direct relations between designed and accomplished bearing capacity parameters of the foundation soil. If the values by the field parameters are within the given criteria limits, then there is no need for their separation. In other words, an execution parameter can be accepted as the design one, as long as the beneficiation processes that could change it are under control. Hence, in the considered project, before and after soil stabilization, SPT and PLT tests have done in order to confirm the soil stabilization. However, execution parameters are not identical to designed geotechnical parameters by their form. The impact zone depends on the soil type, type of the vibrator, deep compaction method and the designed regime of operation. After doing control test with plate load test in 3 different of the project site, impact zone has been considered 0.6 meter and diameter of stone column has been considered 1 to 1.2 meter. Finally, the results have been demonstrated that stone column design for this construction place is desired. Also performing stone column in the mentioned construction place leads to increasing the bearing capacity about 3 times. Therefore, the problems of high settlement and low bearing capacity are solved.

Considering the importance of soil permeability in Civil Engineering and its impact on constructed buildings, the precise study and accurate estimation of the factor in site have a significant role in accurate geotechnical studies. However, usually due to technical and economical problems, drilling boreholes in the site is not feasible and it is necessary to produce reasonable data with current data of boreholes. Therefore, in this research, spatial distribution of soil permeability in Tabriz Subway Domain was estimated by the use of geostatistics tools. The monthly piezometric heads of 21 boreholes obtained from Water Organization of Eastern Azarbaijan were used. In this way, the data of 16 boreholes were used for estimation and the rest 5 boreholes data for the crossvalidation purposes. Generally, the geostatistical tools include two advantages, one is its unbaisness property and second it is possible to compute the estimation variances. These make it possible to verify the performance of the model at each modeling step. Directional variograms showed non-isotropic condition of both soil hydraulic conductivity and ground elevation. It should be noted that to eliminate the dimension dependency of the models in the co-kriging, the values of the data were normalized prior to impose into the model. The study indicates that spherical variogram model is suitable for the geostatistical modeling. Also, the Cokriging system which employs the ground elevation as the secondary variable leads to more accurate results than the Kriging model which is a univariate estimation system.