نشریه مهندسی عمران
سال پنجاه و دوم شماره 8 (آبان 1399)

Disinfection is a process designed to disable pathogens, thereby preventing the transmission of waterborne diseases. An important aspect of chemical disinfection is the design of chlorine contact basins. Chlorine contact systems with sufficient time (contact time) disinfect the water for chemical reactions to inactivate pathogens. Design of chlorine contact basin or chlorine contact tanks is to maximize the phenomenon of Residence time through the flow of spiral of baffles through the basin or contact tank. Historically, chlorine contact tanks have been investigated by empirical relationships, physical model studies, or tracer studies after the construction of a contact tank. Construction of laboratory samples and tracer studies are time consuming and costly. In recent years, computational fluid dynamics models have been used to investigate the flow and processes of solute transport in contact tanks, which is the best way to design contact tanks before construction. In this study, a 3D simulation of the CT-1 contact tank is performed using Multiphysics 5.3a software. Also, several 3D simulations in the CT-1 contact tank, in which the effect of the baffle orientation in a longitudinal direction with three different channel widths was performed, it was concluded that the narrow channel with a ratio of Winlet /Wch=0.68 (channel to inlet width ratio) and Lbo / Wch ratio (baffle opening length to Channel width ratio) equal to 1 has the highest baffle factor and the least amount of Morill index and therefore optimal hydraulic.

By placing the reinforcing elements, the shear strength of the soil improves. Several studies have been carried out on reinforcing of coarse grained soils, and less has been done on fine-grained soils. Researches show that the shear strength of fine grained soil-geosynthetics is weaker than the coarse soils and should be to improve its interaction with reinforcing elements. In this research, soils with about 80% passing the No.200 sieve and two types of non-woven geotextiles have been used. Shear strength of soil was considered by adding polypropylene waste fibers with 0.2%, 0.7% and 1.2% by weight of dry soil. Shear strength of soil – geotextile determined by large direct shear machine and some of these tests were done in vertical loading – reloading conditions. Experimental results show that vertical loading – reloading conditions increase interface shear strength. Addition of 0.7% fibers increase interface shear strength up to 15% and 9% in loading – without reloading and loading - reloading conditions, respectively. Also increasing of normal stress in loading step, geotextile with higher tension strength and reduction of moisture content are factors improving shear strength of soil-geotextile in this study.

In offshore dynamic compaction, the water effect on the depreciation of the pounder impact velocity on seabed and the crater depth created in the soil is always a major challenge. In this paper, the water entry problem of lattice pounders of 9, 16, and 25 holes, with 3x3, 4x4, and 5x5 matrix arrangement respectively, the effect of the number, dimensions and arrangement of the pounder holes, on the impact velocity with simulated soil of the seabed and the crater depth created in it was studied experimentally. The results showed that the impact velocity of the lattice pounders depends on the holes area, and the crater depth created in the soil, the amount of energy transferred from the pounder to the soil and the improvement radius and depth of soil depend on the area of the pounder's lattice web. Therefore, in dynamic compaction of the seabed, increasing the pounder weight without reticulating it cannot considered as a suitable solution to increase the impact velocity on seabed and the effective factor on soil settlement and compaction. Also increasing the pounder weight and its drop height over the optimum drop height lead to increasing the operating costs, and it requires the use of large barges and long cranes with a high load capacity.

It this paper, incremental dynamic analysis (IDA) of the controlled structures is presented. Nonlinear dynamic analyses for controlled structures are performed through Force Analogy Method (FAM) and State-space. IDA curves are demonstrated for un-controlled structures, under optimal control and under semi-active control. Therefore, the influence of control system for structures and changes in its behavior could be observed. Introductions for IDA, structural control, Semi-active Hydraulic Damper (SHD) and Force Analogy Method (FAM) are explained in the article. Full Static Condensation Model (FSCM) is introduced as a recent method that could consider non-linear behavior (through FAM and State-Space), static condensation and full Rayleigh damping matrix. In this article, FSCM is extended for the structures which are protected by optimal or semi-active control system. Therefore nonlinear behavior of controlled structures was considered. Numerical examples for a 5-story frame under scaled earthquakes were presented. The structure, for both controlled and un-controlled conditions, was modeled by the way that it could consider non-linear behavior. Control algorithms that have been used in the program were optimal control and SHD semi-active control. Programming was performed in MATLAB and IDA curves for no-control, optimal control and SHD control (with different arrangements of SHD control tools) are calculated and illustrated. At the end of the numerical section, some results and interpretations were extracted from IDA curves of controlled and un-controlled. They are explained in details and could give better understanding for dynamic behavior of the structures.

Adsorption is one of a common treatment applied in heavy metal removal. Recently, studies of low-cost adsorbent are intensively gain attention to the scientist were usually waste product from industrial, agricultural and food production which produced abundantly. Since most of the structures, ponds, and drainage pipelines are made of concrete, the use of adsorbent concrete can be an effective way to remove pollutants, especially heavy metals from wastewater. In this research, diatomite and sunflower stems were used as concrete additives to adsorb cadmium and nickel from wastewater as well as materials that could maintain and even increase the strength, durability, and stability of concrete in water and wastewater structures. Diatomite was replaced with part of the cement and sunflower replaced with part of aggregates used in concrete. The adsorption of Nickle and cadmium by concrete components (cement, silt, diatomite and sunflower stem) was investigated. Cement was able to remove nickel and cadmium completely. Other components of the concrete also have a good ability to remove nickel and cadmium. The maximum adsorption capacities of Ni and Cadmium for diatomite, silt, and sunflower stem were 2.85 and 1.88, 2.61 and 2.82, 18.45 and 6.82 mgr/gr, respectively. Metal adsorption onto adsorbents was evaluated by Langmuir and Freundlich isotherms. Results indicate that both Langmuir and Freundlich isotherm models are suitable. Concrete pieces removed cadmium completely, but in nickel absorption, the control sample had the best performance

Investigation of the effect of temperature on soil strength is one of the issues which has been considered by many researchers in recent decades. In this study to investigate the effect of temperature on the undrained shear strength (Cu) of clay soils, a cell with the capability of both changing and keeping fixed the temperature of sample, was designed and constructed. After determining the index properties of samples for Kaolinite clay soil, undrained shear strength (Cu) test was carried out on saturated clay soil at 10, 20, 30, 40, 50, 60 and 70 ° C. Repeatability of the results was confirmed by repeating tests on samples with the same properties a given temperature. The results showed that by increasing the temperature, the Cu values decreased so that, as the temperature raised from 10 ° C to 70 ° C, the values Cu were reduced from 26.6 to 10.94 kPa. Accordingly, in the studied temperature range, an empirical relationship between temperature and Cu (with R2= 0.96) was proposed. The general shape of the stress–strain curves of the samples in different temperature was the same and in strain level of 20% was linear. Increasing the temperature caused to decline in the range of elastic deformation and enhancement in the range of plastic deformation of the samples; in addition, by increasing the temperature, the angle of the failure plane was decreased. The measurement of axial expansion stress (AES) indicated enhancement of the stress by increasing the temperature.

Reactive dyes are water-soluble and causes color changes and pH. These colors create problems for humans and plants and animals living in the environment. Therefore, removal of these colors from the aquatic environment is essential. In the present study, grapen-oxide nanosheets were first synthesized using the modified Hammer method and magnetic graphene oxide was prepared using a solothermal method. The properties of nanofillers were investigated using SEM, XRD and VSM analyzes. PES membrane was studied using GO and mGO nanofilers during the phase separation process and the surface and membrane morphology of the membrane using SEM analyzes, porosity and contact angle. After measuring the flux and the properties of the membrane, the removal of RG19 and RR198 by membranes was investigated. The results showed that the hydrophilic property in all modified membranes was improved compared to pure membranes. The PES-mGO membrane has a higher pH than the PES-GO membrane; the membrane containing the PES-mGO has a contact angle of 4.24 degrees relative to the PES-GO membrane. The PES-mGO membrane porosity was higher than PES-GO and the PES-mGO membrane flux, 3.3 L / m2h, was higher than the PES-GO membrane. PES-mGO membrane flux recovery was increased to 5.7% of the PES-GO membrane. The performance of the PES-mGO membrane against RG19 and RR198 removal was 1% and 4% higher than the PES-GO membrane. Regarding the results, it can be said that magnetic nanoparticle graphon oxide has a better efficiency in membrane repair and removes dye from aqueous solutions.

Scouring control in the downstream of the ski jump spillway is one of the most important issues faced by hydraulic engineers. In this study, an experimental investigation was done to evaluate the reduction of the maximum scour volume due to the combination of six-legged concrete elements (A-Jacks) in different hydraulic conditions. These elements were placed in the downstream of the ski jump spillway. The experiments included a single size of concrete element and two sizes of riprap with five discharges and three different tail-water depths. The change in depth of tail-water resulted in the spillway having free, semi-submerged and submerged states. The results showed that as the scour depth increased, the scour rate is reduced significantly. The simultaneous presence of concrete elements and riprap amid different hydraulic conditions caused a 100% decrease to the maximum scour volume when compared to the control tests. The use of A-Jacks when equated to riprap covered structures in a 100 m2 area indicated a 10% reduction in bed protection costs ( By use of Price list ).

in this research, two conflicting objective functions used to solve the problem of optimization operation of Sistan's Chah Nimeh reservoirs. The first objective function defined minimizing the total of second power of difference between agricultural demand and release and the second objective function defined maximizing the reliability index. In this study, to compare the studied algorithms, the criteria of the algorithm's run time, the number of solutions in the optimal Pareto front, and distance, dispersion, convergence and generation distance were taken. The results of the study of Meta-Heuristic algorithms indicated that among MOPSO, MOGOA and MOALO algorithms, MOALO and MOGOA algorithms were more efficient than MOPSO algorithm. According to the performance criteria of the algorithm's run time and the dispersion criteria, the MOPSO algorithm showed high efficiency and according to the performance criteria of the distance, convergence and generation distance criteria, the MOGOA showed high efficiency. According to the performance criteria of the number of solutions on the optimal Pareto front MOALO algorithm showed high efficiency. Also, MOALO and MOGOA algorithms effectively covered optimal pareto front. It can be said, the solutions of these algorithms find in themselves optimal pareto front, create a rich set of optimal solutions that not only effectively cover the optimal Pareto front, but also dominate the solutions of the other two algorithms. Therefore, it seems that none of these performance criteria can alone determine the superiority of an algorithm than other algorithms in solving an optimization problem.

Use of adobe materials is considered as a common construction method in rural and historic cities of developing countries. Compared to other conventional building materials, adobe offers some advantages such as eco-friendly features, local availability, easy application, cost-efficiency, and high thermal and sound insulation. However, the weak seismic performance of adobe buildings under past earthquakes has led to extensive economic losses and casualties. Therefore, retrofitting of such buildings and development of guidelines for their seismic design seem to be vital. In addition, retrofitting of adobe buildings with natural and traditional materials would be more desirable. Due to the critical role of walls as the main load bearing element in adobe buildings, their retrofitting would be of high priority. Towards this, the current study was aimed at utilizing palm fibers as a natural and sustainable material in lateral retrofitting of adobe walls. In total, six adobe wall panels, with dimensions of 1000×900×200 mm, including one control and five retrofitted specimens were tested under the combination of a constant vertical load and incremental lateral displacement reversals. The retrofitting technique involved external application of palm meshes plastered with a straw-mud mortar. The experimental parameter comprises dimensions of meshes, number of anchors on both sides of the walls, and arrangement of meshes. The test results indicated that using externally bonded fiber meshes can led to retaining the overall integrity and change the shear failure mode to a rocking/toe crushing. Further, the lateral strength, ductility factor, and energy dissipation capacity of wall were improved remarkably

Functionally Graded Materials (FGMs) are kinds of composite materials that due to the continuity of mixture of constituent materials as Functionally Graded, have more effective mechanical properties. Also, due to some executive needs, make opening and stiffener in shells will be necessary. Therefore, In this paper, the effective parameters on the free vibrations of Functionally Graded plates with opening and stiffener have been studied. In order to do this, ABAQUS finite element software has been used, in the first, the effect of important parameters such as volume fraction index, geometric dimensions and plate support conditions have been analyzed. The results show that the thickness and volume fraction index have the highest and lowest effects, Respectively, on the natural frequencies of each of the FGM plate modes and with the increase of simple support conditions in the edges of the plate (the decrease of fixed conditions), the natural frequency of the plate decreases. In the following, the effect of opening and stiffener on the natural frequencies of the plate has been observed, that Circular opening has a greater effect on the natural frequency of the plate than the square opening, and also the stiffener thickness has a greater effect on The natural frequency of the FGM plate than its height.

One of the most prominent features of the stepped spillway performance is the considerable loss of energy during it compared with other types of spillway. Considering this feature, obtaining a more detailed view on the energy dissipation parameter and, finally, increasing its amount has been the focus of most studies related to this type of spillway. For this purpose, using a Flow-3D model, the effect of pitched steps (steps with hole) on the velocity and pressure variations, water height at downstream and energy dissipation has been investigated. As well as the appropriate model of the most energy dissipation in the laboratory was developed and studied. Numerical and experimental results show that pitched steps reduces the velocity to about (82-69%) and reduces the water height at the downstream by up to 33%, and the energy dissipation is increased to about 4 times. According to the pressure distribution profiles at the vertical edge of the step, it was observed that the amount of negative pressure in the vertical wall decreased by about 82%, and the positive pressure was approximately increased by 3 and 4 times. The negative pressure on the floor of the steps is turned into positive and the positive pressure near the edge is increased due to the presence of the hole. Also, the results showed that the error rate of the studied parameters in the numerical and experimental models was very low and acceptable, indicating a good fit between numerical and experimental data.

Exchanges of water and solute between stream flow and flow through river bed porous media are known as hypoerheic exchanges. Hyporheic exchanges transfer water and nutrient to the organism lived in the hyporheic zone, so affect ecological conditions and food cycle. One of the important factor effects on these exchanges is pressure gradient along the bed form. Riffle-pools are geomorphic features of rivers which pressure gradient along them drive hyporheic exchanges and recently considered in river restoration projects. The goal of this study is to compare the hyporheic flux and residence time of flow within sediment bed, in 2D and 3D riffle-pool. For reaching this goal, the surface flow simulated with OpenFAOM and then the results of pressure along bed form, set as a boundary condition on groundwater model (MODFLOW software). The results show that, by increasing bed form amplitude, hyporheic exchanges flux increases by 26 percent for both 2D and 3D models, and residence time decreases by 36 percent for 2D and 41 percent for 3D models. Also, comparison of 3D riffle-pool with equal 2D model shows that hyporheic exchanges flux and residence time increase by 3% and 4%, respectively.

Due to structural safety and residential comfort, the vibration control of tall buildings under earthquake and wind excitations has always been one of the important issues in the structural engineering context. One of the well-established approaches for controlling the structural vibration is the use of Tuned Mass Dampers (TMD) employed with different methods in structures. In this paper, a 10-story shear building with linear behavior is studied under twenty eight far-field and near-field earthquakes in MATLAB. Active Tuned Mass Damper (ATMD) is used to control the structural vibration. According to the earthquake excitation random nature, Fuzzy Logic and Mamdani Inference System are applied to determine the control force. In addition, the Particle Swarm Optimization (PSO) algorithm is used to determine the optimum TMD actuator power, and in this optimization, the effect of the actuator saturation is also considered. Furthermore, a method is introduced for robust optimum design of the suggested controller. Using the proposed control system and the optimum actuator power, structural responses decline about 44 pct. Additionally, due to the existence of uncertainty in earthquake records, applying a controller with average actuator power generally results in 33 pct. structural response reduction, and the performance of the active controlled system always outperforms the passive controlled system with 16 pct. structural response reduction.

The composition, texture and microstructure of rocks affect their physical and mechanical properties such as dry unit weight, porosity, p-wave velocity and Brazilian tensile strength. The aim of this study was to investigate the effect of mineralogy sandstone characteristics on physical and mechanical properties of sandstone in three groups with low mean quartz (less than 65%), moderate (65 to 80%) and high (more than 80% ) and 26 samples were collected from southern province of Zanjan city Then, a comprehensive program of rock mechanic tests are planned and mineralogical properties and engineering parameters such as dry unit weight, porosity, P-wave velocity and Brazilian tensile strength were determined and their relationship was investigated using linear regression analysis. The results show that the mineral composition is effective on the strength properties and increasing the quartz mineral content in the samples, two physical parameters of dry unit weight and P-wave velocity and a mechanical parameter Brazilian tensile strength increase. Also, due to the correlation between physical parameters, P-wave velocity can be predicted with appropriate approximation using porosity parameter for sandstone in studied regions and the results can be used in geomechanical studies.

Moisture can damage the rheological properties of bitumen and adhesion of bitumen to aggregates in asphalt mixtures. Many studies have shown that the use of anti-stripping additives can be used as one of the effective methods for improving the quality and enhancing the resistance of asphalt mixtures against moisture damage. Accordingly, in this research, an attempt has been made to investigate the mechanism of the effect of nano-amine anti-nailing materials on the basis of mechanical and thermodynamic methods. 24 different mixes of asphaltic mixes have been investigated using three types of aggregates, two types of base bitumen and three types of anti-scaling additives. The surface free energy components of bitumen were measured using the droplet method and the global absorption coefficient and the ratio of fatigue life of the asphaltic mixtures through indirect traction testing, respectively. The structural properties of aggregates were also investigated using a SEM scanning electron microscope (SEM). The results of this study show that the use of nanomaterials adds to the increase of hydrophobicity and the reduction of hydrophilicity in aggregates. Also, the use of this type of additives will increase the ratio of fatigue life and tensile strength in asphalt mixtures. In addition, nanomaterial additives on bituminous surface free energy components, aggregate surface free energy components, adhesion energy Bituminous aggregate and affinity energy in asphalt mixtures Beth leaves and improves the function of these components is against moisture damage.