AMIRKABIR JOURNAL OF CIVIL ENGINEERING (AMIRKABIR)
Year:2018 | Volume:50 | Issue:4 |Papers Count:19

During the recent years, Gabion weirs have been taken into consideration due to their compatibility with the environment, positive effect on river’ s water quality and their simple design and implementation. In this research, the Hydraulic parameters of flow around broad crested gabion weirs (BCGW) with various side slopes are investigated. Overall, a number of 21models comprising 7 various geometries each with 3 different porosities including (43%, 44%, 46%) and in 10 to 6 different discharges were simulated and studied. Results indicated that the discharge coefficient (Cd), through flow discharge and energy dissipation increased by increasing the average diameter of particles. In addition, Increasing the area of the porous media by changing side angles from 0? to 60? reduces the dischrge coefficient and through flow discharge. At final stage, experimental equations are presented using Nonlinear Multivariable regression analysis in order to calculate the discharge coefficient and through flow discharge of these structures.

According to available statistics and information and given the population growth as well as the ever-increasing development of agriculture, there is an upward trend in withdrawals from surface water and groundwater resources in different regions of the country such as Mahabad to provide water for the region. The optimal conjunctive use of surface and groundwater resources is one way to providing the water demands in crisis and drought situations. In this study, a management model based on effective techniques of optimization and simulation has been developed to solve the optimization problem. Variation of groundwater table level in Mahabad plain was simulated using GMS software initially. Then based on the results of this simulation, artificial neural network was trained to use in simulate-optimization system. Genetic algorithm was used to solve the optimization problem. The results indicate that this model is powerful and effective for solving large-scale problems and optimal conjunctive use of surface water and groundwater resources of Mahabad. Based on the results obtained of the research and running of optimization conjunctive use quantitative model, the share of water supply of water resources, is respectively 13. 5 percent and 86. 5 percent of surface water and groundwater resource.

Phosphorus is one of the essential nutrients for plants which is major pollutants originating from non-point sources such as urban runoff, residential, industrial and agricultural areas. Runoff movement and erosion result in Phosphorus loss from watershed and entering the waterbody. The aim of this study was to investigate the Phosphorus release from watersheds under different land-use in Guilan Province. These watersheds included Divshel, Komsar, Jokolbandan, Sangar and Saravan. Samples were taken monthly from the runoff of these watersheds during one year. Then, some properties of runoff including electrical conductivity and acidity of runoff, total solids, total suspended solids and total dissolved solids were measured by weighing method; moreover, three types of phosphorus, total Phosphorus, water-soluble phosphorus and particulate phosphorus were determined as well. The results showed that the highest loss of total phosphorus was relevant to Sangar with forest and agricultural land uses in February (0. 228 mg/l). Phosphorus variations in these watersheds were dependent on the amount of monthly precipitation and phosphorus loss was increased with augmenting rainfall. The maximum mean of water-soluble phosphorus losses were related to Jokolbandan with the dominant land use of forest (0. 36 mg/l) and Saravan with land uses of forest and industrial activities (0. 33 mg/l), respectively. Furthermore, the highest loss of particulate phosphorus was from Sangar in April (0. 192 mg/l). The level of phosphorous losses from the studied watersheds was high enough to result in eutrophication of water bodies and consequently water quality decline.

Every year by flooding in various parts of the world a large number of bridges are destroyed just when its need to used widely. Most of this bridge destruction are due to scour around their piers. Erosion and the movement of the bed materials due to water flow is called scour. During this process, a hole is developed around piers and progress to reach to a depth of equilibrium gradually. For this research a laboratory flume with 6m length and width of 73cm located in the hydraulic laboratory of the Shahid Chamran University of Ahvaz was used. In order to reduce the scour around pile groups a flat plate with small thickness called collar are installed around the middle set of the pile groups. The collars used were netted with four percent 0% (simple collar) of 30%, 50% and 70% and they were installed in three levels, on the bed, 0. 5D and 1D above the bed. The experiments were conducted under clear water condition and three Froude Number were equal to 0. 12, 0. 14 and 0. 16 and the results were compared with the case of piers without collar. The results showed the simple collar located on the bed and netted collar with 70% of opening located on the level of 0. 5D relative to the bed surface in both cases the reduction of scour in the front pier were equal to 86 percent compared to non-collar and these cases had the highest performance.

The metallic dampers are one of the most widely used energy dissipation devices that can be used in building and non-building structures such as bridges. U-shaped metallic strips are among these tools. The effects of some parameters such as the number and arrangement of connection bolts on the cyclic behavior and energy dissipation capability during earthquake events will be evaluated in this study using nonlinear finite element method. According to the numerical results, elimination of the bolts in the FEM modeling has not significant effects for the longitudinal cyclic loading, but causes incorrect results for the transverse cyclic loading. Also, in the latter case, contrary to the former one, the number of connecting bolts is a significant parameter affecting the cyclic behavior of the damper. In this loading condition, it is observed that an increase of the number of bolts can increase the stiffness and strength of the U-shaped damper.

Due to the high amount of CO2 emission through the production of cement and great energy consumption in the cement industry, one of the most important issues in concrete technology is to find out an appropriate replacement for Portland cement. Alkali activated materials are the new approach for solving this problem. In fact, alkali activated concrete consists of an inorganic structure containing two parts: Source material and alkaline activator liquid. In this study, the effect of the amount of source material and water to binder ratio on chloride ions ingress was evaluated. For this purpose, 5 mix designs were used to make alkali activated slag concretes and for activating slag, 6 molar potassium hydroxide and sodium silicate solutions were employed as alkaline activator liquid. Additionally, one mix design was dedicated to ordinary Portland cement concrete for the sake of comparison.The properties of AAS concretes were examined by means of slump loss, measurement of compressive strength at the ages of 1 to 180 days and capillary water absorption test at 7, 28 and 90 days. Furthermore, chloride ions penetration was measured through electrical resistivity test, rapid chloride migration test (RCMT) and resistance against chloride ions diffusion test according to NT Build 443. The results indicated that the performance of water to binder ratio and also the amounts of source material were comparable to that of ordinary Portland cement concretes. Additionally, alkali activated slag concretes had higher compressive strength and also superior durability against chloride ions penetration compared to OPC concretes.

As railroad is responsible for a major share of freight transportation compare with other in-land transportation modes, appropriate grouping and scheduling of the freight wagons can lead to significant decrease in emissions exhausted by diesel locomotives. In this study, we evaluated the impact of different freight wagon grouping and scheduling policies by simulating moving trains on Iran’ s railroad network. The simulated model is accounting for scheduling, classification and train formation simultaneously. To consider the variation of demand for freight transportation of Iran’ s railroad network according to different grouping and scheduling policies, eight scenarios designed in addition to do-nothing. Therefore, the values of main pollutant including? CO? _2,? SO? _2, PM,? NO? _x, CO and HC emissions are calculated for each scenario by simulation. Results show that simultaneous implementation of non-necessary grouping policy and flexible scheduling policy can lead to lower amount of total emissions. The conclusion provide useful suggestion on grouping policy for Iran railroad network.

Carbon dioxide and carbonation in concrete structures after several years may leads to corrosion of the reinforcements, and consequently reduces the life of concrete structures. According to reports of IPCC, uncertainty to predict the weather conditions is very high. The annual growth rate of carbon dioxide concentrations from 1. 4 ppm during the period of 1960 to 2005 has increased to 1. 9 ppm during the period of 1995 to 2005. Two predictions of A1F1 and A1B are presented for changes in carbon dioxide concentrations. In A1F1 high economic growth, population growth will continue in the mid-21st century with high speed, and the use of fossil fuels will also continue as before. In A1B, using clean energies is common. In fact, A1F1 and A1B are respectively pessimistic and optimistic predictions for the concentration of carbon dioxide in the environment. According the analysis results base on Monte Carlo simulation, global warming and climate change lead to an increase in average temperature of Earth and atmospheric carbon dioxide concentrations, and finally, it can reduce the durability of concrete structures. Also, it was observed that ignoring changes in concentration of carbon dioxide can have a significant effect on the results obtained for carbonation depth. It was also observed that considering each of predictions for changes in carbon dioxide concentrations does not substantially influence the depth of carbonation.

One of the disadvantages of ultra-high performance concrete (UHPC) is high content consumption of cement which leads to high level of material cost compared to ordinary concrete. Therefore, finding appropriate supplementary cementitious materials could reduce the environmental CO2 emission due to the reduction of cement consumption and may enhance the mechanical properties of ultra-high performance concrete. In this study, the pozzolanic activity of five industrial waste materials including silica fume, glass powder, copper slag, coal waste and silica floor has been investigated. It is expected that these materials in concrete can react with calcium hydroxide from cement hydration and produce C-S-H compounds. The pozzolanic, mechanical and diffusivity properties of ultra-high performance concrete made from the aforementioned materials as well as the pozzolanic properties were studied under standard and thermal treatment from 3 days up to 120 days. The results showed that the temperature and time are two significant factors on the performnce and pozzolanic activity of materials and use of higher curing temperatures led to improved mechanical properties for the mixtures containing silica fume. However, higher curing temperatures led to weaker durability and mechanical characteristics of UHPC with the other supplementary cementitious materials.

This paper intends to assess the existing Iran seismic design loads code (standard No. 2800) through comparing with those of New Zealand seismic code due to their apparent similarity such as; their two parts spectral acceleration form. Both standards represent the seismic hazard level of ten percent chance in fifty years. The assessments made are: the basic design acceleration (A) (in 2800), and the hazard factor (Z) (in NZS), the constant acceleration and constant maximum velocity period ranges of the two spectral shape forms on the four types of site soil conditions, and the directivity effects representative parameters, [N(T), in 2800] and [N(D, T), in NZS]. The 2800’ s spectral accelerations on the four soil types including the FD-pulses are assessed by a hazard-based FD-pulse method. The results of this study quantitatively expose that the existing 2800 s’ spectral accelerations need to be increased at relatively small period ranges of 2 s while get smaller at the period ranges longer than 2s. In other words, the design requirement of spectral accelerations, corresponding to the structures which are widely under construction in near field sites, are smaller than those of the rationale hazard-based values.

Most traditional soil improvement methods are time consuming, expensive, require heavy machinery and are environmentally detrimental. As a potentially more environmentally favorable ground improvement method, biomediated soil improvement offers an alternative to traditional soil improvement techniques. This method is based on microbial precipitation of calcium carbonate. The role of bacteria is producing urease enzyme to catalyzing hydrolysis of urea. In the presence of calcium ions, the produced carbonate ions in hydrolysis of urea, react with the calcium ions and calcium carbonate sediment was formed. This paper investigates the applicability of biomediated soil improvement in modification of dry loose sand by surface percolation. To evaluate the success of treatment, a series of laboratory experiments was conducted, including, shear wave velocity, unconfined compressive strength, Brazilian tensile strength, calcium carbonate content and etc. The study has revealed that biomediated improvement technique caused the improvement of strength as a result of the cementation of sand particles. Furthermore, surface percolation method has the potential of cementation and stabilization of loose sand with desirable depth. Increase in strength and calcium carbonate content decreases with increase of depth. Results also shows that increase of strength due to bio-improvement depends not only to calcium carbonate content but also to its spatial distribution in pores and particle-to-particle binding numbers.

In this study, we are using to help optimize the combination of neural networks and genetic algorithms (GA), slip threshold and volume stability of optimal operation Gables earth embankment dams be determined. Also, the stability coefficient of r Gables earth dam with a neural network to determine and outputs Plaxis finite element software has been compared. For neural network training data from 150 models in the earth dam Plaxis finite element software is used. Sustainability analysis to determine confidence gable at the desired level of slip and rupture process of determining the most likely and the least confidence about it, is done, the application of genetic algorithms in this research, the process of determining the most likely slip rupture threshold (minimum coefficient sure) is. Also, another study uses genetic algorithms in optimal amounts of dam embankment operations are such that the minimum safety factor (sliding threshold) is achieved. In this research easier for engineers to use the dimensions proposed, using different Azmshkhsat weir dam in the soil, for different heights and the results of analysis took the form of graphs and tables provided, the use of these charts can be optimized dimensions and volume of concrete Without referring directly to the program won.

Soil reinforcing is one of soil improvement methods by using of reinforcing materials (with suitable performance in tension) in soil (with fairly compressive strength and weakness in tension). In recent years, numerous studies have been carried out about the application of reinforced soil and bearing capacity of granular soils. Generally, these studies are limited to reinforced embankment with geosynthetics and steel stripes and even plastic parts. So using of plastic waste to improve the bearing capacity of embankment has not been considered. Therefore, in this research the effect of plastic wastes to improve the bearing capacity of granular soils has been investigated. The variables considered are using one type of disposal plastic wastes in different weight percentages at irregular (random) reinforcement and regular reinforcement (with specified layers) in granular embankment. The research was carried out in small laboratory scale using CBR tests. According to results, placing plastic waste parts in sandy soil increases the bearing capacity remarkably. The optimum values were obtained at 2% to 2. 5% plastic weight ratios to soil weight. Also the required energy conditions to attain optimum percentage were investigated. In this regard, the strain-stress behavior of soil was studied. The results show that increasing of plastic parts to 2%-2. 5% at irregular and regular condition, respectively, raises the soil elasticity coefficient to 234 and 152% respectively.

Nowadays, RC or Combined diaphragm walls are vastly used for deep excavation. This type of retaining structures consists of some piles, which are tied-back using the anchors and anchored from their toe to the ground. Concrete or wood plates were used between them. In order to evaluate the effects of some parameters on wall deflection and its internal forces, several models of combined diaphragm walls were selected and analyzed using FLAC software. Before developing the models, Lim and Braiud (1999) case study was modeled with FLAC2D and results were compared with the experimental results indicating acceptable accuracy of the modeling. The numerical model simulates the soldier piles with beam elements and the anchors with cable elements. The soil model used is a modi? ed hyperbolic model with unloading hysteresis. The complete sequence of construction is simulated including the excavation and the placement and stressing of the anchors. The numerical model is calibrated against an instrumented case history. Then a parametric study is conducted. The parameters which is evaluated are: distance and stiffness variation, the bonded and un-bonded length of the anchors, the angle of the anchors and the first raw anchor location. By comparing the different parameters it was observed that the variation of the flexural stiffness of the soldier piles and variation of the bond length of the anchors contain the highest and lowest effect on the maximum horizontal displacement of the wall, respectively. Other analytical results consisting wall deflection vs. geometric characters of the wall are presented and discussed.

The foundation shape effects on the stress distribution induced in the soil. Moreover, it has influence on the failure mechanism of the soil. For these reasons, it plays an important role in the ultimate load capacity of the foundation. Due to lack of materials, the new design methods attempts to utilize the least amount of material and achieve the maximum efficiency. If shell elements are employed in foundations, and the interaction effects are considered, their required cost can be reduced. This paper aims to compare the performance of the composite annular shell foundation with that of the annular one. For this purpose, the ultimate load capacity and the settlement of these foundations are experimentally modeled for various shell angles. Findings prove that the ultimate load capacity of the composite foundations are more than that of the annular one. Furthermore, it is observed that increasing the shell angle reduces the ultimate load capacity. Moreover, the shell efficiency factor is decreased by increasing the soil relative density. This phenomenon shows that the shells perform more appropriately in low-density soils. Additionally, a novel relation is proposed for predicting the ultimate load capacity of the composite shell. It is worth emphasizing that adding the edge beam to composite foundations improve its performance in settlements during failure. Moreover, the efficiency of foundations with edge beams is more than the ones without beam in soils with any density. Hence, usage of shells in annular foundation enhance its ultimate load capacity.

There are small cracks in rocks; therefore, when rocks undergo loading, stresses are concentrated at the tip of cracks causing rock fracture before reaching its ultimate strength. The critical value of the stress intensity factor at the crack tip is called fracture toughness. The tensile strength of rocks is weak; therefore, Mode I (tensile mode) is the most critical loading mode. In some cases, rocks continuously experience heating-cooling. Therefore, it is necessary to determine the effect of heating-cooling cycle number on mode I fracture toughness, which is the objective of this research. To achieve this objective, we conducted three-point bending test on semi-circular specimens of three types of natural rock including sandstone, limestone and andesite to determine the mode I fracture toughness. A series of concrete specimen was also tested for further investigation. The specimens were heated up to 700° C in 1, 5 and 10 cycles and then cooled. A series of experiments were also conducted on the specimens at room temperature (25 ° C). According to the rising of temperature in firing process, the rate of temperature rise for specimens in the electric furnace is determined to be 15 ° C per minute. Fracture toughness of andesite rock, sandstone and limestone specimens decreases under cyclic conditions. Results indicate the generation and expansion of micro fractures in some rocks after undergoing cycles of heating-cooling, which causing an increase in the effective porosity and decrease in the P-wave velocity in rocks.

This article proposed project risk management model based on different project phases with emphasis on building phase and installation considering risk management in powerhouse projects. Accordingly, a case study on Manjil Wind Farm was conducted to firstly detect the most important risks of building phase and installation in this project considering different arbitrary risks and then, to propose the risk management model to evaluate the impact, the possibility of diagnosis and risk incidence, and their impact on the main purposes of this project which are time, quality, expenses and security; moreover, a model was proposed to prioritize the detected risks in this project based on group opinions and AHP method, and the following results were gathered. After determining about the detected risks priorities, react or response programs to critical and important risks were provided and the consequence of react or revision actions in risk management program were recorded with offering some comments.