نشریه مهندسی عمران و محیط زیست دانشگاه تبریز
سال چهلم شماره 3 (پیاپی 63، زمستان 1389 و بهار 1390)

In this study, the stress-strain behavior of lightweight aggregates concrete (LWAC) made of local Scoria and Pumice aggregates in Azarbaijan-Iran has been studied. Fourteen different concrete mixes with different mix proportions were used in this work. Forty-two cylindrical specimens made of different concrete mixes were prepared for uniaxial compression test to determine the stress-strain behavior of the LWAC. The trend of the experimental results were compared with the existent mathematical relationship defined by other researchers. There were some differences between the experimental results and existing equations which can be related to different properties of the LWAC in comparison with those of normal and high strength concrete (HSC). The experimental results can result in lower flexural strength of the beams than that of the existing relation by other researcher, which implies more attention to be paid on it.

Study of groundwater quality trend in any region is very important from the view of scheduling and sustainable water resources management. In the present study trend analysis conducted on groundwater quality based on information of 13 piezometeric stations located in the Ardabil plain from 1374 to 1387 using the non-parametric Mann-Kendall test. The effect of significant lag-1 autocorrelation removed from the data series prior to analysis. Hydrogeochemical variables studied here are Total anions, Total Cations, pH, TH, EC, SO42-, Na%, Na+, Mg2+, K+،Ca2+, TDS, SAR, Cl- and Hco3-which are measured two times a year. The trend of line slope is estimated by Sen’s estimator method for each time series. Results showed that concentration of all groundwater quality variables exhibited upward trends at all stations. Statistical significant positive trends observed for 23 percent of stations in wet month and 19. 5 percent in dry month of a year. Results for slope of trend lines were shown by Box and Whisker plots. In wet month strong positive trends observed for water quality in the central and east part of the Ardabil plain. However, in wet month such positive trends observed in the central and east of the plain under study.

Concrete pavements are subjected to light and heavy traffic loads and different climatic conditions. Salt scaling is a major durability issue for concrete and concrete pavements, so the phenomenon has been the subject of extensive research efforts in the world. Salt scaling is defined as superficial damage caused by freezing a saline solution on the surface of a concrete body. The damage is progressive and consists of the removal of small chips or flakes of material. This study examines the performance of concrete made of modified Portland (type II) and composite cements, with and without entrained air bubbles subjected to the salt scaling and proposed mechanisms, are discussed. Visual inspection results and rate of mass loss due to salt scaling for every five cycles of freezing - thawing are presented. This study shows that surface strength of concrete plays an important role on salt scaling resistance. Entrained air bubbles in concrete reduce bleeding and will result in increased surface resistance. Therefore, entrained air bubbles improve concrete salt scaling resistance. Results show that performance of type II Portland cement was more appropriate than the composite cement for mixture without air bubble in salt scaling test. The mixture containing composite cement with entrained air bubbles shows the best performance in salt scaling test.

One of the most important types of the environmental loading on a seawall is the wave induced force during the storm conditions. In such conditions, free surface of the water has a time dependent irregular pattern which can be described by either a time series or an energy spectrum. The wave induced pressure on a seawall is random in nature and consequently, the internal forces produced in the body of the seawall have a random temporal change. The flexural moment and shearing force are the most important internal forces which can be minimized by selecting an optimum value for the slope of the seawall. In order to find an optimum slope which leads to minimizing the wave induced internal forces, a large number of seawalls have been modeled and analyzed subjected to sea waves, using the FE software package, SACS. Different values have been assigned to the slope of the seawall ranging from –45˚ to +45˚ with the increments of 5˚. It must be noted that 1˚ increments have been considered in the critical regions. In order to increase the accuracy of the results, the structure’s weight and the hydrostatic pressure have been considered during the analysis. The results of numerical analysis showed that when the slope is 15˚, the flexural moment at the base of the seawall is minimized. Hence, it can be concluded that the optimum value for the slope of the studied seawall is 15˚ which can be adapted for design purposes

Rivers as one of the most important sources of fresh water consumed industrial, agricultural and urban areas have special importance. Challus River as one of the rivers of Mazandaran province residential areas and agricultural pass and eventually flows to the Caspian Sea is of importance. Therefore, comprehensive research done about the pollution in terms of quantity and quality and use of management tools such as mathematical and computer models to determine the trend and forecasting river water quality and pollutant load to determine the damage and offer solutions for improving the quality of the type. In this study, the measured data and statistics about the water quality at four stations of the river and compare them with existing standards status of this river were studied. Self-purification river model with soft ware QUAL2K New Profile quantitative and qualitative input river and wastewater in the two low water season and high water, was built and calibrated. Then it convey wastewater to the standard profile (with respect to effluent discharge standards, the Department of Environment) discharge to surface waters of the river with the new situation use its software and the user in different areas and rivers were determined to limit its quality standards available for agriculture, livestock and seafood consumption. The result was the conclusion that power has been low river Self-purification increase in organic nitrogen wastewater with new is of considerable. The results indicate that the Self-purification of river low by increasing organic nitrogen influent wastewater. Also, by increasing of inorganic phosphorus during the rise of water level in the river phosphorus and organic phosphorus river water. The nitrate level in the river during high water season which decrease trend due the dinitrification and release of N2 is. But in low water season nitrate initially fixed at the end cause influx of sewage to where the base flow is low and pollutants will be increased. While low levels of nitrate indicate that it was contaminated by fertilizers discharge into the river. The main problem at the end of the river in new modeling and urban domestic waste water was diagnosed. Creation of networks residential wastewater and to introduce the treatment methods keep the river water quality to be safe.

Progressive collapse refers to a phenomenon in which a local damage of a primary structural element leads to the failure of partial or whole structural system. To investigate the progressive collapse of structures, nonlinear dynamic procedure leads to more accurate results than static procedures. Nonlinear dynamic procedure is very complicated and the evaluation or validation of its results may be very time-consuming. Therefore using simplified methods are very important. This paper presents a simplified and accurate analysis procedure for progressive collapse analysis of steel structures. The results of the proposed method showed to have good agreement with nonlinear dynamic analysis results. Also, the capacity curve obtained from dividing the accumulated area under the nonlinear static load-displacement curve by the corresponding displacement of the column-removed point is used to predict the progressive collapse resistance of the column-removed structure.

In the Eccentric braced frames (EBFs), which one end of the link beam is connected to a column, the safety of the link-to-column connection is a requirement for the ductile and safe performance of the EBF. But among of the tests that have been implemented on this connection yet, because of the intensity of forces on vulnerable region of the link-to-column connection, the tested specimens were confronted with brittle and sudden failures. So it seems that the reduced beam section (RBS) can be a suitable solution for raising this problem, by concentrating flexural stresses at a location away from the connection, in flexural yielding link beams. Therefore in this paper, the possibility of keeping the plastic hinge away from the location of link-to-column connection, in the meanwhile achieving the required plastic rotation of link beam, by using the RBS connection, were investigated. This evaluation was done by using a finite element program ETABS and with nonlinear static analysis (pushover) for a dual system of special moment frame and special eccentric braced frame. According to the present work, the models with RBS by earlier developing the hinge at the RBS region, delay yielding occurrence of link at the column face. So the yielding does not occur at the column face, at least prior to achieving the moment at the location of RBS region to 1.1 times of its expected plastic moment capacity.

With growth of technology and different industries dependent to electricity, construction of hydroelectric power plants for utilizing water stored in dam reservoirs is an important issue in different countries in the world. Increasing efficiency and performance of dams and hydroelectric power plants has been the most important object which has studied in recent years. Genetic algorithm is a useful optimization tool which has been considered by researchers in many fields. The goal of this study is to optimization the penstock dimensions using genetic algorithm. Penstock is a high pressure pipe that conveys water from dam reservoir or any high head water to power plant turbines. For this purpose, penstocks of Shahryar dam in Miyaneh and Shasta dam in U.S. have been investigated. With doing sensitivity analysis, a suitable structure is presented for genetic algorithm. The results indicated that genetic algorithm method has high capability in optimization and can reduce penstock volume considerably and acceptably.

Aerobic granulation is an environmental biotechnology developed for the purpose of high-efficiency wastewater treatment. The distinguishing characteristics of aerobic granules attribute superiority to this technology in comparison with the conventional activated sludge processes. Increase in process stability, higher density, stronger microbial structure, higher biomass retention, good settling ability and ability to withstand high organic loading are such advantages of aerobic granules over conventional activated sludge. In this research, COD removal efficiency with glucose carbon source was evaluated by aerobic granules in SBAR (Sequencing Batch Airlift Reactor) with a 4 hours cycle time. To investigate the role of polymer adding in aerobic granulation, two reactors simultaneously were used. R1 and R2 were determined respectively as control and polymer adding reactors with working volume of 4.5 L. Experiments were done at different organic loading rates (OLRs) ranging from 0.72-5/4 kg COD/(m3.d). The results represent the high capability of aerobic granules in COD removal and yellow and large-sized black filamentous granules with diameters of 0.5-7 mm were formed in the reactors. With high settling capability of granules, sludge volume index (SVI) decreased to less than 100 mL/g. Finally it was indicated that adding of chitosan polymer had positive impact on granulation so that R2 produced 17% and 27% yellow and large-sized black filamentous granules more than R1, respectively.

Dam failure is one of the important problems in dam industry. Serious damages in case of dam failure, enhance importance of this problem. Regarding to complexity of dam breach phenomenon, existent models are often insufficient. Nowadays, Artificial intelligence (AI) approaches such as artificial neural network (ANN) and genetic programming (GP) are used for modeling this complex phenomenon. In the present study, the ANN and GP were used to estimate peak outflow discharge from earthen dam breach. For this purpose, historic dam failure data were used to create models. The model results show that both ANN and GP are in good agreement with the observed values, while they depict better results than existent classic methods.