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The use of pozzolans is very necessary and inseparable for the sustainable development and better performance of the concrete industry. In the production of concrete, the combination of iron powder, fly ash, metakaolin and limestone powder under the name of fracking is used as materials and substitutes for cement in different percentages. The compressive strength of this concrete is higher than normal concrete. This type of concrete is a very new concrete that few tests have been done on it in the world, so there is not lot of information available about it. According to the studies, the most important features of this concrete are the use of iron waste, reduction of air and environmental pollution, cost savings and higher compressive strength than ordinary concrete. In this research, in order to protect the environment and reduce environmental pollution, fracking has been used as a relative substitute for cement. After obtaining the appropriate proportions, the frac mixture with percentages of 0, 3, 6, and 9 was considered as a substitute for cement. There were 8 tests in this research, 4 tests of the first category were carried out with the mentioned percentages of frac and 0% of steel fibers, but in the 4 tests of the second category, the volume of 1% of steel fibers was considered in the mixture. In this research, a total of 16 concrete samples were made, of which 8 of the first batch were used for pre-heating tests and 8 of the second batch were used to collect the results and performance of the concrete after heating. took After making the concrete samples and performing the necessary processes, the concrete samples were molded and placed on the vibrating table in order to make them denser and prevent voids in the concrete. After vibrating for a sufficient time, the samples were placed in the open space for 24 hours and then placed in the water basin for the processing process. A group of samples was taken out of the pond after 7 days to perform compressive and tensile strength tests (at the age of 7 days, due to the freshness of the concrete, exposure to high heat was not done) . After 28 days, the second batch was removed from the water and prepared for testing. The tests performed on these samples include compressive strength before and after heating, bending strength before and after heating, ultrasonic before and after heating, and water absorption before and after high heat. To test the performance of the samples after heating, the samples were placed in the furnace at a temperature of 450 degrees Celsius for 60 minutes (one hour) and after one hour, the samples were removed from the furnace and The samples were cooled at a temperature of 24 degrees Celsius. After the cooling of the samples, the tests were conducted on the samples, and the results indicated that the increase in the amount of frac leads to a 16% increase in the compressive strength before heating and improving its mechanical properties compared to ordinary concrete.

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The effective design of structures resistant to seismic vibrations is one of the main concerns of structural engineers to deal with damages caused by earthquakes, which can withstand more earthquake forces with methods such as energy dissipation. Recent earthquake records show that the earthquake record characteristic of the near area differs from the earthquake records of the far area. Among these characteristics, it can be mentioned that the pulse-type state of these records, as well as the high maximum speed and ground displacements. For this reason, these types of records increase the seismic requirements of the structure compared to normal earthquakes. The map of faults and seismic zoning of Iran shows that important urban points such as Tehran, Tabriz, etc. have high seismicity and are located near the fault. Therefore, it is necessary to design and build structures that can properly withstand the features of near-fault earthquakes, this issue reveals the understanding and recognition of the behavior of structural systems and the structure's response to the special features of near-fault earthquakes. This article first investigated the seismic evaluation of three existing 4, 8, and 12-story steel structures with lateral load-resisting systems. Then the desired structure was strengthened using a friction damper, and finally, the acceleration recorder was applied to the structure in the near- and far-fault earthquake zone case study. The seismic demand of the retrofitted structure was investigated in ANSYS Workbench finite element software, which was done in the form of modal analysis, floor drift displacement, structure acceleration response, and von Mises stress. For seismic validation, a two-story, single-span steel frame has been used. The dynamic load used was 0.5g based on the north-south component of the El Centro earthquake (1940) with a maximum acceleration scaled to 50 cm/s. To validate the numerical results, the horizontal displacement of two points on the first and second floor was compared with experimental data, and an acceptable accuracy was obtained. The results of the maximum acceleration at the highest point of the building showed that in a far-fault earthquake zone, the best effect of dampers was on 8-story buildings with a 77% decrease, and in a near-fault earthquake zone, it was related to a 4-story building with a 66.4% decrease in acceleration. Stress in near- and far-fault earthquake zones, the best effect of dampers was on 4-story buildings with 83% and 84% reduction, respectively. In a far-fault earthquake zone, the best effect of dampers was on 8-story buildings with a 44% reduction in maximum displacement, and in a near-fault earthquake zone, it was related to a 4-story building with a 61% reduction in acceleration.
 

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Shotcrete, a pneumatically sprayed concrete mixture, has gained significant popularity in the construction industry due to its versatility and adaptability. However, the demand for high-strength shotcrete has intensified, driven by advancements in equipment and admixtures. Fiber-reinforced high-strength shotcrete (FRHSS) offers enhanced quality, adhesion, and construction speed, making it ideal for stabilizing excavations and slopes, strengthening masonry and concrete structures, and reinforcing underground structures. Additionally, the increased strength allows for reduced section dimensions, leading to more economical designs.

This research investigates the effects of aggregate gradation and admixtures, including micro silica, superplasticizer, accelerator, and micro recycled steel fibers (MRSFs), on the strength and performance of FRHSS. The study employs wet-mix and dry-mix shotcrete methods, examining the properties through laboratory and field experiments.

The results demonstrate that achieving high-strength shotcrete is more feasible with the wet-mix method. Fiber-reinforced wet-mix shotcrete attained a 28-day compressive strength of 987 kg/cm², representing an 80% and 77% increase in compressive strength and energy absorption, respectively, compared to conventional fiber-reinforced wet-mix shotcrete. Furthermore, fracture toughness tests revealed that MRSFs effectively prevent microcrack propagation and control deformations. FRHSS incorporating MRSFs exhibited a 28% and 97% increase in compressive strength and energy absorption, respectively, compared to the corresponding mix without fibers.
 

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Fire can not only lead to many human and financial losses, but also can cause structures to collapse and destroy them. For this reason, it is necessary and inevitable to protect buildings against fire and conduct more research in the field of better understanding the effects of combining different materials with each other and obtaining materials with greater resistance to fire. Concrete and concrete structures are always used by construction engineers due to their resistance, availability and resilience against fire. Ordinary concrete loses its strength at high temperatures, and the use of unreinforced concrete is not very useful due to its brittleness and weakness in tensile strength. In concrete, the tensile strength is lower than its compressive strength, and for this reason, researchers are trying to increase the resistance to fire and heating by improving the tensile strength of concrete. Reinforcing concrete with rebar is always a solution to increase the tensile strength in concrete parts, one of the most important weaknesses of using rebar in concrete is that the reinforcements form a small part of the concrete cross-section and actually cause the concrete to be inhomogeneous. In this research, double-bent steel fibers have been used to overcome the mentioned weakness and reinforce the concrete. It should be noted that concrete containing steel fibers has favorable compressive and tensile strength due to the high tensile strength of steel fibers. In order to achieve this goal and achieve fiber concrete that has good fire resistance, we defined seven different mixing plans with different percentages of steel fibers and lubricants. Concrete samples were produced using double-bent steel fibers in amounts of 0.5, 1, and 1.2 percent by volume of concrete and superlubricant in 0.5, 1, and 1.3 percent by weight of cement, and then in Cubic molds with dimensions of 10x10x10 cm and cylindrical ones were sampled as standard, and after setting the cement, the 28-day-old concrete samples, after heating and placing inside the electric heater with different temperatures, were divided into two The method of gradual cooling with ambient air and fog spraying (water spraying) is similar to what firefighters do when extinguishing a fire, after measuring the amount of weight loss of the heated samples, the weight loss values ​​were presented in the form of a diagram, then the samples were subjected to tests Compressive strength, tensile strength (Brazilian test) and ultrasonic wave speed (ultrasonic test) were placed, and the results and data of each of them for each mixing design were presented in the form of a diagram after examination and classification, so that the effect of high heat on Concrete containing steel fibers and super-lubricant should be determined. The results clearly showed the improvement of the tensile strength in three volume percentages of fibers by 14.6, 16.8 and 64.5%, respectively, compared to concrete without fibers, and also the compressive strength of concrete after bearing the heat of 250 degrees Celsius and cooling to the fogging method had 44.5, 31.6, and 9.3 percent, respectively, and in the gradual air cooling method, the compressive strength was 43.3, 44.9, and 50 percent, respectively.


 

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The design of earthquake-resistant structures and the reduction of damages caused by them have always been considered. One of the ways to reduce earthquake vibrations in steel frames is to use cable braces. In addition, one of the ways to improve the behavior of the structure against seismic loads is the use of dampers. In this research, magnetorheological damper and cable brace are used simultaneously. To check the effectiveness of the proposed system, four steel frames including, a steel frame without cables and dampers, a steel frame with cable braces, a steel frame with magnetorheological dampers and, a steel frame with cable braces along with magnetorheological dampers, which have one-span and two spans, were selected and the behavior of this frame Assuming different conditions, under nonlinear static lateral load and seismic loads, it has been checked in SAP2000 software. By examining the results obtained from the nonlinear static analysis of the case of a one span, it is concluded that the steel frame with cable brace and magnetorheological damper reduces the lateral displacement of the frame and often the internal forces of the beam and column more than other frames. gives by examining the results of the time-history dynamic analysis of one-span and two-span conditions, it is concluded that the proposed system reduces the lateral displacement of the frame and the internal forces of the beam and column more than other frames in most of the investigated earthquakes. In other words, using the proposed systems improves the performance of the structure against lateral loads.

 

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Steel plates are widely used in various industries, especially in civil engineering. Low cost in implementation and reduction of seismic mass are the advantage of steel shear wall system compared to other structural systems. The goal of a good design is that along with following the existing guidelines and achieving the desired seismic resistance of the structure, the structure is affordable in terms of weight and cost. Considering that according to the design, it is not possible to achieve the optimal use of the structure's capacity by force control method, the theory of uniform deformations was proposed with the assumption of a constant performance level. The subject of design based on performance increase the safety of the structure against earthquake force and design with optimal seismic performance during the useful life of the structure in seismic areas. Also, compared to the design method based on force control, it can lead to a lighter and economical design.
One of the significant ways to reduce the weight and stiffness of shear walls and boundary elements connected to them is to limit the connection of filler plates to boundary elements. In this method, limiting the length of the connection reduces the force on the beams and columns, and as a result, smaller sections can be used.
In this research, in order to achieve the optimal performance level, two concrete frames with steel shear wall resistant system are subjected to nonlinear analysis. Then, the initial evaluation of the behavior and the correctness of the used method are checked. After that, the effective factors in achieving uniform stress in the height of the structure will be investigated. For this purpose, by using the effect of the thickness parameter and the appropriate pattern of connection of the shear steel plate to the surrounding elements, the way of changing the performance and behavior of the structure will be investigated. For this purpose, 3- and 4-story concrete frames with steel shear wall systems were modeled using ABAQUS^TM finite element software. The steel used in the steel shear wall system is ST37. First, the connection of steel shear plates to floor beams was considered and then the influence of the partial connection pattern on the seismic performance of the steel shear wall system was investigated. The modeled frames were subjected to dynamic analysis, linear and nonlinear buckling analysis, and cyclic analysis. Based on the obtained results, the property of energy dissipation in the frame with a steel shear wall system with partial connection has increased significantly. Changing the partial connection pattern led to changing the maximum in-plan relative displacement. Also, the surface of the stress distribution shows that in the partial connection, the stress concentration mainly occurred in the place of the steel shear plate connections. In addition, according to the results of cyclic analysis, considering the partial connection of the steel shear wall has led to a decrease in the average energy absorbed in the structure and an increase in its ductility. Also, changing the connection pattern has affected the average amount of absorbed energy in different loading cycles.

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Aims: Fatalistic employees take serious risks because they have limited knowledge of risks and accidents, leading them to under estimate the possibility of their occurrence. This research examined the effectiveness of safety training on changing employees’ fatalism with attention to the mediating role of attitude toward safety issues. Methods: 204 employees was selected according to the stratified random sampling method in Isfahan Steel Company, divided randomly into control group (n=103) and experimental group (n=101) and the questionnaires of safety attitude and fatalism were applied as data collection instruments. The data was collected before intervention, and educational intervention was then executed in four 90-minute sessions over four days. One month after intervention, post-test was performed and the collected data was analyzed using descriptive indexes, t- and F-tests. Findings: Results show that there was a significant statistical difference in average numbers of attitude toward safety issues and fatalism before and after training intervention (p<0.01). Also, mediation analysis indicated attitude toward safety issues mediated the effect of safety trainings on fatalism (p>0.05). Therefore, safety training only by promoting workers’ safety attitudes can change the fatalistic beliefs among employees. Conclusion: By understanding relationship between fatalism and safety attitude, it should be possible to improve the training of employees, such that are less likely to attribute accidents to chance or fate.

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The current study suggests the utilization of steel wool as an extended anode electrode in an electrochemical process to en­hance the efficiency of Remazol Brilliant Blue R (RBBR) re­moval from wastewater. The effect of the operating parameters of initial pH, applied current, supporting electrolyte, and initial dye concentration on textile dye removal efficiency was inves­tigated to determine the optimum conditions of the process. Ki­netic studies were performed in the optimum conditions. Scan­ning electron microscopy (SEM) and x-ray fluorescence (XRF) were carried out to determine the morphology and characteri­zation of the extended anode surface. Under the optimum con­ditions, the dye and chemical oxygen demand (COD) removal were obtained 99.42% and 72.72%, respectively. The reaction kinetic data of the electrochemical process was followed by the pseudo-second-order kinetic rate equation (R² = 0.99). These findings might be useful in treating the various pollutants in industrial wastewater.

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Supply Chain Management (SCM) is an integrated process of decision making from supplying raw materials to consume final product by final customers. Selecting of most appropriate suppliers is one of the most important decision making problems affected by different qualitative and quantitative parameters. As supply chain gets more complex, uncertainty and risk level in the supply chain would increase. Hence supply chain risk management, especially supplier risks, has become a major issue in the organizations. In this study at first by identifying suppler risks in the steel industries using blast furnace, a hierarchical classification of risks (38 risk events in 3 levels) was developed. At the second step, by considering risk events set, a group of nine evaluation criteria was proposed. Afterward for more accurate assessment of each supplier risks, a composite risk index is proposed based on the evaluation criteria and their importance weights. Finally, by employing the ELECTRE III, the priority of suppliers (mines) of Esfahan Steel Company was evaluated and the most appropriate one was determined. Based on obtained results, Jalal-Abad and Shargh-Iran iron ore complexes can be considered as suppliers having lowest and highest risk levels, respectively.

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Various thermo mechanical processes have been studied to improve the mechanical properties of 18Ni-Co-Mo steels. In this work, the effect of interpass aneal time on the mechanical properties of the 18Ni-Co-Mo steel was investigated, using the rolling experiments. Hot rolling process was performed in two passes. The reduction of area was 30% in the first pass at 1100 °C. After first pass specimens were air cooled to second pass temperature (900°C) and held for various interpass time (2 sec, 5 min and 10 min). The second pass was performed at 900°C for 20% reduction of area. After that, the specimens were directly water quenched to retain the microstructure present at the second pass. Tensile and charpy tests samples were machined from hot rolled specimens. The results showed that grain size was decreased significantly at these conditions by increasing the interpass time from 2 sec to 5 min. This was attributed to the static recrystallization. With an increase in interpass time to 5 min, tensile strength was increased, without significant change in charpy impact energy. Increasing the interpass time from 5 to 10 min, increased austenite grain size. This was attributed to the grain growth. The results indicated that the interpass time of 5 min can be considered to obtain the maximum tensile strength.

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Thermal fatigue (heat checking), mechanical fatigue, wear and plastic deformation of critical areas of hot forging dies at working temperatures are the main mechanisms that reduce their lifetime. During forging processes the surfaces of the dies reach temperatures of 700-800 ºC. Therefore, hardfacing of these areas with nonferrous elevated temperature hardfacing alloys such as Stellite 6 can improve the performance and lifetime of the dies, many times. Hot hardness, galling resistance, hot corrosion and oxidation resistance, adhesive wear resistance, low friction coefficient and absence of allotropic transformation up to 1100 ºC are the most important properties of Stellite 6. H11 tool steel is widely used as hot forging die material. This steel because of its high alloy contents and, therefore, its hardenability is very sensitive to high cooling rates involved during welding cycles and hydrogen induced cracking (HIC). For this reason, in this research hardfacing parameters of H11 tool steel with Stellite 6 in TIG welding method have been investigated. According to the results, hardfacing of this steel in annealed hardfaced condition isn't feasible and it is recommended that preheating and intermediate temperatures during the hardfacing cycle between 310-370 ºC. The suitable current for TIG hardfacing of this steel by φ3.2mm filler rod was determined to be 80-85 amperes for the first layer and 90-100 amperes for upper layers. The minimum thickness for obtaining maximum hardness in the hardfacing layer (41-42 HRC) under these conditions was determined to be 3mm. It is recommended that the effective heat input for hardfacing of this steel under three-body heat transfer conditions would be less than 455kJ/m. It is also recommended that the Δt8→5 of H11 tool steel hardfacing cycle would be in the range 6 to 15.3s. Finally it is recommended that H11 hardfaced tool steel would be stress relived in the range 425 -500 ºC for 1 hour per 30mm base metal thickness.

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Calculating the cost of product precisely and presenting reliable information and reports for economic decision making are the objectives of cost accounting systems. But, the independent auditors reports reveal that most of the manufacturing companies, especially state companies, do not possess suitable methods for cost accounting of products. To identify the insuficiencies of cost accounting systems of these companies, two companies, involved in steel industry were selected and operation process as well as working methods of their different part were examined. The results show that the cost accounting system of the selected companies, compared to a suitable accounting system is very in appropriate. The reasons of its inappropriateness are absence of proper procedures for production cercufation, absence of accounts related to production process, absence of correct information a bout the capacity of production lines, inability to recognize costs behavior, not using proper bases for over head allocations, not using budget mechanism related to list of the bills, not colwlating and registering variances and not preparing reliable managerial reports at certain periods of time.

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In this study, in addition to forming a steel tube of D6AC by direct flowforming, in order to examine the effects of different parameters of heat treatment process on the a for mentioned part properties, different cycles of heat treatment process are designed and after doing so, mechanical properties and microstructural changes of flowformed tube are investigated. For this purpose, at 850, 900 and 950 ˚C austenitizing temperatures for 15 and 30 minutes and AUS-BAY quenching at 510 ˚C for 10 minutes, and then quenching at 60 ˚C oil are used. Initial tempering for 2 hours at 250 ˚C and final tempering for 2 hours at 250, 300, 350 and 450 ˚C was performed. Investigations show that the optimum heat treatment cycle is austenitizing at 850 ˚C for 30 minutes, and final tempering at 300 ˚C, because of creating high strength and suitability for fracture toughness. Due to small grains of initial austenite, the ductility properties are also adequate.

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Considering the vital role of Environmental factors alongside industries’ efforts on effective and efficient use of resources as well as nowadays’ social issues, lead to serious attention to sustainable development. On the other hand, the intensity and necessity of environmental considerations in the steel industry, which has decades of history in Iran, has always been emphasized. Therefore, this paper aims to elaborate the underlying factors of steel industry sustainable development. To this aim, based on prior studies and interviewing experts, the underlying extracted factors scrutinized through ISM approach in order to develop a coherent structure. In the following, the structured factors clustered by MICMAC analysis. In addition, their mutual affects and importance weights, derived by employing ANP on the ISM developed structure. Findings depict that inventory, occupational accidents, human safety and welfare are the most effecting factors of steel industry sustainable development.

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Ohmic heating has an advantage over conventional indirect heating methods because heater (electrode) surfaces temperatures are comparatively lower as heat is generated within bulk fluid. Conventional ohmic heating under typical low frequency alternating current (50 or 60 Hz) could cause hydrogen and oxygen evolution due to electrolysis of water. This process could develop the electrodes decay or corrosion. Any decay or corrosion of electrodes shorten the life time and contaminate the food. The main objective of this study was to investigate the rate of the electrodes corrosion in the ohmic heating process. For this purpose the concentrations of Fe, Cr, Ni, Mn, and Mo from the stainless steel electrode migrated into ohmic and conventionally treated soup were measured. In this study migration of the major key metal ions from stainless steel measured by Atomic Absorption. The results showed that overall ohmic treatment yielded the same migration residues of all metal ions, compared to the conventional retorting with similar electrodes. Concentrations of all metal ions migrated into food samples after ohmic treatment were far lower than dietary exposure levels so that this technique can ensure the safety and quality of food supplies.  

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This study is concerned with a correlation between the microstructure and mechanical properties of 42CrMo4 steel which was subjected quenched-tempered and step-quenching heat treatment. Quench tempering and step quenching heat treatment produced a tempered martensite and an equiaxed Ferrite-Bainite-Martensite (F-B-M) microstructure, respectively. Tensile test results indicated a yield drop effect in F-B-M microstructure with ferritic matrix. This effect was not observed on the specimens with tempered martensite and F-B-M microstructure with hard phase B-M matrix. This effect can be attributed to dislocation generation in ferrite phase during bainitic and martensitic transformations. Fractographic investigations indicated intergranular cleavage in F-B-M microstructure and micro-void coalescence in tempered martensite microstructure can be attributed to carbide formation in martensitic structure during tempering micro-void coalescence in tempered martensite microstructure

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Abstract In this paper the effect of two types of common initial geometric imperfections on the reliability of steel frames is investigated. These imperfections are the coordinates of connection nodes and crookedness of members. Most finite element reliability analyses in past literature neglect this source of uncertainty. For this purpose static nonlinear pushover structural analysis is used from which reliabilities are estimated based on FORM and Monte Carlo sampling methods. Furthermore to investigate the importance of uncertain parameters, reliability sensitivity analysis is performed by use of the direct differentiation method which has been implemented in the object oriented software framework Open Sees. It is demonstrated that some of these geometric imperfections have significant influence on reliability assessment of steel frames.