Showing 399 results for Sign
Volume 18, Issue 6 (12-2018)
Abstract
The procedures for measuring, mixing, transporting, and placing heavyweight concrete are similar to those used in conventional concrete construction; however, special expertise and thorough planning are necessary for the successful completion of this type of concrete .The use of heavyweight concrete in construction is a specialized field, Heavyweight concrete is used in counterweights of bascule and lift bridges, but it is generally used in radiation shielding structures to absorb gamma rays and differs from normal weight concrete by having a higher density and special compositions to improve its attenuation properties. When heavyweight shielding concrete is used to attenuate neutrons, sufficient material of light atomic weight, which produces hydrogen, should be included in the concrete mixture. Some aggregates are used because of their ability to retain water of crystallization at elevated temperatures, which ensures a source of hydrogen not necessarily available in heavyweight aggregate Cements would be suitable for conventional concrete and produce the required physical properties, are suitable for use in heavyweight concrete. Low-alkali cement should be used when alkali-reactive constituents are present in the aggregates and a moderate or low-heat cement should be used for massive members, To avoid high and rapid heat of hydration and resultant cracking, it is advisable not to use Type III cement or accelerators unless the concrete temperature is controlled by specially designed refrigeration systems. Thorough examination and evaluation of heavyweight aggregate sources are necessary to obtain material suitable for the type of shielding required. These sources are limited, and a material survey should be conducted to determine availability, chemical and physical qualities. The supplier’s sources should be inspected to evaluate rock composition, abrasion resistance, and density since these properties may vary from one location to another within a deposit. The purchaser must realize that mineral ores are not as uniform as normal weight concrete aggregates and make appropriate allowances Limited resources and increasing use of concrete, particularly in the industrial production cause that the heavyconcrete be useful. In order to optimize production of heavyconcrete, the most basic parameters that must be changed is the mix design. Optimization of the concrete mixture design is a process of search for a mixture for which the sum of the costs of the ingredients is lowest, yet satisfying the required performance of concrete, such as workability strength and durability. For this purpose, heavy concrete mix design optimization model is firstly defined and then optimal mix design will be achieved, by using an optimization algorithm. The experimental data were utilized to carry out analysis of variance. To develop a polynomial regression model for compressive strength in terms of the five design factors ( cement, coarse aggregate, fine aggregate, water and density ) considered in this study The numerical results shows that the amounts of coarse aggregate and cement are simultaneously reduced and amount of the fine aggregate is increased in the optimum mix design. Considering mass production concrete in nuclear power plants, this optimal mix design methods and reduce the cost of concrete can greatly reduce the cost of construction
Volume 18, Issue 7 (12-2016)
Abstract
Bambara groundnut [Vigna subterranea (L.) Verdc.] is an indigenous legume crop in Africa. It has comparable value to other legumes for food and nutritional security in the continent. However, small-scale farmers continue cultivating unimproved landrace varieties over the production areas in sub-Saharan Africa. Bambara groundnut landraces exist as heterogeneous mixtures of seeds, which typically contain a few to several seed morpho-types that may embrace wide genetic diversity. In this study, the agro-morphological variations of 213 Bambara groundnut landraces were evaluated to determine the presence of within- and between-landraces of pod and seed morphology, out of which only 49 were used to access their genetic variability using 9 agronomic traits while 158 landraces were used to determine leaf morphology. Most of the landraces displayed pointed, round and yellowish pod colour, with grooved and oval seed shapes. For leaf morphology, 49.4% had round leaves, while 21.5% had elliptical leaves, with 55.7% landraces being heterogeneous possessing more than one leaf shape. Significant differences (P< 0.05) were detected for seed traits and leaf morphology including seed height, canopy spread and terminal width. Leaf morphology could be a useful marker for strategic breeding and genetic conservation of Bambara groundnut.
Volume 18, Issue 7 (12-2016)
Abstract
Computer-Supported Collaborative Learning (CSCL) is a new trend in educational sciences. This study investigates how knowledge sharing and transferring can be facilitated by using CSCL in a problem-solving setting. Intervention of research is education regarding Sustainable Water Resources Management (SWRM) by Computer-Supported Collaborative Learning (CSCL). The purpose of this research was to determine whether change of knowledge was accomplished after utilization of CSCL in agricultural MSc. and PhD. students of Science and Research Branch University, Ahwaz, Iran. Education by CSCL was accomplished in a two-week period. As a part of the experimental design, 173 university students were randomly assigned and divided to four groups. The first group with 43 students was labeled pretest-posttest treatment group (E). The second group, with 44 students, labeled pretest-posttest control group (C1), only received face to face education, which was known as the control group. Thus, we compared the effect of the treatment between the first and second group. The third group as the posttest-only treatment group (C2) received the CSCL, with 44 students, and the fourth group as posttest-only control group (C3) with 42 students did not receive the treatment. The results showed that there was significant difference between posttests knowledge score of C2 and C3, and E and C1. Also, there was a significant difference between pretest and posttest in the experimental group. This result indicated the impact of treatment (CSCL) on the knowledge level of students. In addition, F-test analysis showed there were significant differences among posttests in all groups.
Volume 18, Issue 9 (12-2018)
Abstract
In this paper, a systematic approach is considered to Design an optimal hypersonic Nozzle of a shock tunnel. After assigning the requirements and accomplishment of conceptual and preliminary design phases, a modern optimization strategy based on genetic algorithm and a CFD solver has been used to fine tune the nozzle convergent divergent contour. In this way, parameterization of the overall nozzle contour was done with a few control points and a Bezier curve. This arrangement showed a good flexibility to generate appropriate curves for nozzle shape. Design objectives were evaluated with a N-S viscous solver with a two equation turbulence model. Three objective functions were scalerized in a term with summation of weighted parameters: minimum total pressure loss, Mach number uniform distribution along test section and minimum axial flow deviation. A number of geometrical and physical constraints such as nozzle length, throat area, inlet and outlet diameters and inlet boundary conditions were also considered and finally, an optimized nozzle contour showed a significant improvement of about 3% in quality of the Mach 6 flow in the test section.
Volume 18, Issue 9 (12-2018)
Abstract
The purpose of this article is to optimal manned space launch system conceptual design methodology with combination of modular design (by using clustering the existing motors to provide the thrust force) and sensitivity analysis (by varying the affected parameters to achieve the capability) approach. This methodology is implemented according to the human departure to space program and higher strategy document (country’s aerospace development comprehensive document). To this end, in the methodology is utilized both of the statistical and parametric (the space launch system optimized main parameters) methodologies, is determined the optimum thrust level based on the three fundamental requirements (number of stages, number of engines in clustering and maximum axial acceleration). These fundamental requirements are affected on risk and manned space launch system axial acceleration. In the paper, the purpose of sensitivity analysis is to determine of value of effective of main design parameters on space launch system capabilities. The method for optimizing and design space searching is utilized from Genetic Algorithm (GA). Finally, the suggested methodology and mass – energy capabilities will be verified by comparing the results of two methodology (statistical and optimal) to achieve the specific mission.
Volume 18, Issue 9 (12-2018)
Abstract
Recently, a new approach called Transmissibility based Operational Modal Analysis (TOMA) has been presented in order to identify the dynamic characteristics of structural systems that determines the modal parameters of structures using the concept of transmissibility. In the TOMA approach, unlike OMA methods that use the assumption of white noise input, no limiting assumption is considered for the input excitations, and the modal parameters of structural systems are extracted based on the features of transmissibility matrix. The transmissibility methods, like other frequency domain methods, do not present very satisfactory results in identifying the damping values. Therefore, in the present paper, a new combined method called Fourier Spectral Transmissibility-Wavelet Transform (FST-WT) is proposed which, in addition to determining the natural frequencies and mode shapes of the system, also addresses the exact detection of damping values based on the features of wavelet transform. In this research, the capability of the FST-WT method in identifying and extracting the modal parameters of a 5-DOF system under free vibration is investigated using the responses obtained from the MATLAB Simulink model. For this purpose, the frequencies and mode shapes are respectively extracted from the inverse of the second singular value and the first left singular vector of transmissibility matrix, and the damping values are also determined using the single frequency signals (wavelet coefficients) obtained from wavelet transform based on the minimal Shannon entropy criterion. The comparison of the identification results shows a good agreement with the exact values.
Volume 18, Issue 112 (6-2021)
Abstract
In this study, the effect of different amounts of skim milk powder (SMP) (5 to 11.5%), milk protein concentrate (MPC) (1 to 5%) and soy flour (0 to 5%) on acidity, pH, viscosity and sensory characteristics (flavor, color and overall acceptance of concentrated yogurt were investigated using mixture design. The results of acidity and pH showed that increasing the MPC and SMP decreased the acidity and increased the pH of the sample significantly, while increasing soy flour increased the acidity and decreased the pH of the samples. The results of viscosity showed that only the linear effect of SMP and the MPC on the viscosity of samples was significant and increasing of SMP and MPC increased the viscosity of samples but soy flour had non-significant effect on the viscosity of the samples. The results of sensory score also showed that with increasing SMP and MPC, flavor, color and overall acceptance of samples increased significantly, but increasing soy flour decreased the sensory score. The results of variable importance in projection in PLS regression also showed that SMP had the highest positive significance and soy flour had the highest negative significance in terms of pH, viscosity, flavor score, color score and overall acceptance. The optimum formulation was obtained using numerical optimization algorithm in
in Design Expert software were SMP 9.8%, MPC 1.72% and soy flour 1%.
Volume 18, Issue 118 (12-2021)
Abstract
In this research design and manufacture of home baking machine with baking process control is followed. Therefore, the machine is designed and manufactured with the ability to produce an Iranian flatbread at each baking stage. By choosing the heat flux pattern and different thicknesses of the bed and the height of the baking chamber, the temperature and mass distribution in the three areas of the baking bed, bread and baking chamber is obtained. Image processing, texture analysis and sensory tests are used for evaluating of baked bread under different conditions. Geometrical conditions, boundary conditions and patterns of heat flux are the main factors that influence the baking process and quality of bread. The results showed that bed thickness performs better than higher thicknesses. By increasing the height of the chamber at three heights of 2, 4 and 6 cm, the mean temperature of the chamber decreases. Therefore, the height of the 2 cm chamber is the best one. In the study of bread baking with simple apparatus, it was found that the cooking time of 6 minutes and the beginning baking temperature of 160 °C are the most suitable cooking conditions. The porosity of the bread baked is much lower than that of the bakery one. The texture analysis tests showed that the hardness, gumminess, and chewiness of the heat flux pattern profile 22 had the closest values to the control bread
Volume 18, Issue 119 (12-2021)
Abstract
Oleaster Powder can be used to enrich and improve the nutritional value of gluten-free baked products, which often have low fiber content, due to their desirable nutritional properties such as minerals, vitamins and rich in dietary fiber; therefore the aim of this study was to enrich gluten-free bread with Oleaster Powder and create a new product with suitable texture and nutritional quality; for this purpose in this study, the effect of replacing of Oleaster Powder at levels 0-30% with gluten-free flours (chickpea flour, Rice flour and corn starch) on physicochemical, textural and sensory properties of gluten-free bread was evaluated based on response surface methodology (RSM). The results showed that by increasing the level of Oleaster Powder moisture content, ash, fiber, antioxidant capacity, lightness (L*) and yellowness value (b*) of the samples significantly increased and the amount of fat, protein, carbohydrate, calories and redness (a *) of the samples decreased (P <0.05). Also the water activity was not affected by the factor (P>0.05).With increasing the level of Oleaster Powder, the firmness and gumminess of breads increased significantly. On the other hand, at levels higher than 7.5% of Oleaster Powder, specific volume, cohesiveness and resilience of samples decreased and the loss weight of samples increased (P <0.05). In spite of increasing springiness and chewiness of samples with addition of Oleaster Powder, they were not statistically significant (P>0.05). According to sensory evaluation, the sample containing 7.5% Oleaster Powder had a higher overall acceptance. Finally, the results showed that the sample enriched with 7.5% Oleaster Powder had desirable properties compared to other samples and can be used as a pragmatic raw material in the production of gluten-free breads with high and desirable nutritional value.
Volume 18, Issue 120 (12-2021)
Abstract
Mixing wheat flour with other food sources in order to achieve useful nutritional properties to improve physiological and metabolic effects of Cereal products is highly significant. Flour tortilla is a light, flat, non-fermented, and round bread which is mainly made of wheat, Corn and barley flour. In this research, the Mixture Design Technique was used to analyze the effect of simultaneous replacement of soy flour and whey powder on textural and sensory properties of flour tortillas. The independent variables were wheat flour (٪0-%100) soy flour (5%-15%) and whey powder (2 - %%10) .The results show that changing the ratio of all variables had significant effects on the physicochemical properties studied, statistically. By increasing the replacement level a decrease in Aw of product was observed. So that, use of whey powder and soy flour in their highest proportion, significantly reduced the sample thickness whereas adding high proportion of wheat flour led to the production of thicker samples. The results from the TPA tests revealed that there is a meaningful relationship between all variables and texture properties. Samples containing less whey powder demonstrated better mouthfeel and taste. Finally, optimization displayed that the best formulation of the production of protein-rich tortilla contains 83.2% wheat flour, 12.6% soy flour and 4.2% whey powder.
Volume 18, Issue 121 (3-2022)
Abstract
This study aimed to investigate the effect of replacing wheat flour with spinach powder (0-30%) as a rich source of fiber and minerals using a mixture design based on D-optimal on physicochemical properties (weight loss, moisture, ash, protein, fat, fiber, antioxidant capacity, color, specific volume, height, water activity) and textural and sensory properties of bread. According to the results, with the addition of spinach powder moisture content, ash, fiber increased but weight loss, protein, fat, specific volume, water activity and height of the samples decreased, significantly. The antioxidant capacity of supplemented bread with spinach powder was significantly higher than the control sample (p <0.05). Also, textural properties including firmness and penetration energy were significantly increased by adding spinach powder. Spinach powder supplementation led to a decrease of L *, a *, and an increase of b* in the samples. According to the results, replacing wheat flour with spinach powder up to 7.5% improved the overall acceptance of the samples.
Volume 19, Issue 1 (5-2016)
Abstract
Objective: Breast cancer is considered a heterogeneous disease, characterized by different biological and phenotypic features which make its diagnosis and treatment challenging. We have sought to investigate the expression levels of key components of the Hedgehog signaling pathway, correlation between the signal transducer Smo, and clinicopathologic features (lymph node metastasis and metastasis stage) in invasive breast carcinoma. Also, we examined the inverse correlation between expression levels of Smo and Claudin-1 (an important gene involved in cell tight junctions).
Methods: In this case-control study, we assessed 36 pairs of tumor and adjacent normal tissue specimens obtained from patients with invasive ductal breast carcinoma. The expression levels of key components of Hedgehog signaling (Smo, Gli1 and Ptch), Claudin-1, E-cadherin, and MMP2 were measured by qRT-PCR. The correlations between Smo expression with some clinicopathologic parameters were also analyzed.
Results: We found up-regulation of Hedgehog signaling in invasive breast carcinoma samples compared to normal adjacent tissues. Upregulation of the signal transducer Smo correlated with tumor stages and lymph node metastasis of the breast tumors. Interestingly, this correlation was affected by the expression of Her2. A significant correlation existed between expression levels of the signal transducer Smo and Claudin-1, E-cadherin as an epithelial cell marker, and MMP2 as a metastasis-related gene in advanced metastatic tumor samples.
Conclusion: Taken together, our study revealed a new layer of molecular complexity which should be considered in the management of patients with invasive breast carcinoma. The results suggested a key role for Hedgehog signaling in invasive breast carcinoma. In terms of the inverse correlation between expression levels of Claudin-1 and Hedgehog signaling, Claudin-1 could serve as a candidate gene in diagnostic studies. Thus, its clinical significance should be further clarified.
Volume 19, Issue 1 (1-2019)
Abstract
Pulsed eddy current (PEC) technique is commonly used for the detection of sub-surface defects in electrically conductive metals. However, due to the limited penetration depth of eddy currents, the detection of sub-surface defects in ferromagnetic metals is limited while using PEC technique. In order to extend the application of PEC technique for the detection of sub-surface defects in ferromagnetic metals, the penetration depth of eddy currents needs to be increased. For deeper penetration of eddy currents in the material, magnetic saturation of the tested specimen is a useful solution. In magnetic saturation state, the magnetic permeability of the ferromagnetic metal is decreased and stabilized and, as a result, the penetration depth of eddy currents is increased. In this paper, the performance of the PECT for detection of sub-surface pitting defects in the magnetized ferromagnetic specimen has been investigated through finite element modeling (FEM) and experimental studies. The tested specimen is a 10mm-thick steel plate, in which sub-surface pitting defects with various depths have been modeled. A probe consisting of a driver coil, a pickup coil, and a ferrite core is used to measure the time-varying PEC signals. Then, the time domain features of the differential PEC signals are extracted and used to detect the sub-surface pittings. The results indicate that PEC technique together with magnetization can effectively detect sub-surface pitting defects.
Volume 19, Issue 1 (1-2019)
Abstract
This article investigated design and construction of a 4-DOF delta parallel robot’s components and additionally inverse kinematics and kinematics control of the robot. The initial and final version of the robot based on existing needs, the addition of gearboxes due to the low torque of motors, and flange transformations to connect the gearbox to the robot's base were also discussed. In the following, by simulating the robot in MATLAB software, the integrity of the inverse kinematic equation of the robot was investigated. In the other part, the design of the kinematic control in the joint space was discussed and the results were plotted in the graphs for a z-direction. By designing a suitable robot controller, tracing the desired path and comparing its results with other controllers become possible. By designing a conveyor for the robot and equipping it with a camera, detecting the objects that the robot moves them become possible with image processing. For the purpose of picking and placing the objects, the robot's end effector is equipped with a controlled suction. The results, through which the paths crossed, showed the designed PID controller for the robot was working correctly and the desired path was followed with small error.
Volume 19, Issue 2 (3-2017)
Abstract
Ultrasound-assisted extraction was used to determine the optimum processing conditions and to achieve the maximum extraction yield and viscosity of the gum extracted from quince seed. Using Response Surface Methodology (RSM) to design the experiments and adopting the Central Composite Rotatable Design (CCRD), the effect of extraction temperature (25-55°C), time (3-10 minutes), and pH (6-8) were evaluated on efficiency of gum extraction yield (%) and viscosities (mPas). The Chemical composition of the extracted gum was determined using AOAC standard methods. Apparent viscosity of the gum was measured by rotational viscometer. Using multiple linear regression analysis, a second-order polynomial model was developed for each response. The quince seed gum showed pseudoplastic behavior. Optimum operating conditions based on the highest yield and viscosity was predicted by RSM as an extraction temperature of 38.03◦C, pH of 6.35 and the extraction (ultra-sonication) time of 7.68 minutes. At this optimum point, extraction yield and viscosity were 14.09% and 52.4 mPas, respectively.
Volume 19, Issue 2 (7-2019)
Abstract
Results of traffic assignment models are the main output of transportation planning studies and decision making for future developments is based on these results. Therefore, accuracy of these models is very important. Despite the mentioned importance, comparing the models and their solving methods to estimate actual traffic volume and network performance measures is rarely considered in previous studies. The traffic assignment process has started from the simplest methods like All-or-Nothing, then it has developed using the rules and supplement assumptions such as Wardrop principles and finally it has evolved by concepts such as Fuzzy theory. Traffic assignment models can be categorized by various factors into several groups: deterministic vs. stochastic, congestion considering vs. unconstrained capacity and being equilibrium or not. The main goal of this paper is a comparative and quantitative analysis of various traffic assignment methods to estimate the observed traffic volumes. In this regard, the main questions that this study seeks to answer is as follows: 1- Do the results of various traffic assignment methods have a significant difference in terms of overall network indices? 2- Is there a significant difference in the accuracy of traffic volume estimation in various traffic assignment methods? In this study various traffic assignment methods such as All-or-Nothing, Incremental, Stochastic, User Equilibrium, Stochastic User Equilibrium and System Optimum have been examined. To compare the results of traffic assignment methods, in addition to estimated link volumes, various performance measures such as vehicle-kilometers traveled, vehicle-hours traveled, fuel consumption and air pollutants emission are also used. In this regard the city of Qazvin is selected as a case study. This city has more than 400 thousands inhabitant, near 46 square kilometers area, 113 traffic analysis zone (TAZ) and its network has 2300 directional links and 1200 nodes. The results of applying these methods in Qazvin city network show that various traffic assignment methods based on User Equilibrium, despite different assumptions, have no significant difference in estimating the overall network performance measures as well as estimating traffic volume in links (correlation between estimated and actual link volumes using all of these models is approximately 0.88). But the other methods, which do not consider equilibrium assumption and volume-delay functions, produce different results (correlation between estimated and actual link volumes using all of these models is approximately 0.70). Although estimated link volumes in some of traffic assignment models are significantly different, overall network performance measures are approximately the same. In all of assignment models the differences between estimated and actual link volumes in average are high which are not negligible (approximately 20 percent). In addition to high average error in estimating link volumes, the distribution of these errors has significantly high standard deviation (approximately 20 percent). In spite of different and complicated assumptions, models and solving algorithms in various traffic assignment methods, on basis of Kolmogorov-Smirnov (K-S) test results, the distribution of links volume estimation error is not significantly different. According to this fact, it seems that should be careful in using the results of traffic assignment models to compare and assess minor network improvement alternatives, such as changing conventional streets function to pedestrian streets, upgrading intersections to interchanges, cross section widening, traffic signals optimization and changing traffic direction in streets.
Volume 19, Issue 3 (12-2015)
Abstract
Land Increasing from day to day human need and infeasibility of its production in particular make the practice of its operation and management to be undertaken in a suitable manner. In this connection, the attitude toward land use management and rural residential land assignments in particular has been accomplished to appearing too problems from an old and primitive development viewpoint. Therefore, over recent years, the attitude toward land use management and rural residential land assignments in particular has been made from a sustainability viewpoint. In Iran, like some other countries, the government has attempted to assign national wastelands within a residential land plan to the rural people since 1979. In this connection, yet scientical appraisal has been not for rural settlements ranking affected of consequences of rural residential lands assignment. On the other hand, ORESTE method has been introduce as a one of the most applicational ranking methods recently. Therefore, research aim is introduce and use ORESTE method for rural settlements ranking affected of consequences of rural residential lands assignment. According to the study findings of the research done by the description and analysis of 264 rural household questionnaires Foundation in six selected provinces, and 15 questionnaires of the scientical specialized to have weight to 20 indexes, Chahkotah rural, Abtavil and Malekabad are suitable as compared with other rural areas in residential lands assignment process. In addition to, ORESTE method as a criterion for ranking of consequences of rural residential lands assignment is suitable method and minimum wrong.
Volume 19, Issue 3 (10-2019)
Abstract
Global water scarcity and air pollution by greenhouse gases have amplified the need to use of unconventional water and environmental friendly materials in the concrete industry. Because of its proximity to the Caspian sea, the geological conditions and hydrogeological characteristics of the northern and western regions of Golestan province, groundwater in this area is very salty. On the other hand, due to lack of access to good quality surface water in most of the months, civil and construction activities in this area are always challenging. Accordingly, the present study was conducted to investigate 120 treatments (including three levels of water quality including tap water, briny grounwater and mixture of equal ratio of tap water and briny grounwater), four levels of zeolite (including 0, 10, 20 and 30 percent of zeolite application instead of cement in the concrete mix design), two levels of cement content (including 250 and 350 kg.m-3) and five curing ages (including 3, 7, 21, 56 and 90 days) in three replications. Considering the considerable types of the experimental treatments in this study and in respect to the lack of statistical analysis in previous studies, the results of this study were analyzed based on a completely randomized design with factorial experiment using analysis of variance (ANOVA) and means comparison (LSD) tests. Averagely, use of briny groundwater resulted insignificant increase in the compressive strength of concrete specimens compared to tap water, while combined water significantly decreased this property, but this reduction was within permissible range 10 percent based on national and international standards. Also, replacement of 10, 20 and 30 percent of cement by zeolite compared to non-zeolite treatment significantly reduced the compressive strength of concrete specimens by 9.9, 9.5 and 23.1 percent, respectively, but the difference between replacement level 10 and 20 percent was not significant. However, Concurrent use of briny groundwater and zeolite up to 20% can be recommended without significantly reducing the compressive strength of concrete. In the cement content of 250 kg.m3, the difference between tap water and combined water treatments was not significant, but the use of briny groundwater resulted significance increase in compressive strength of concrete pieces by 22.8 and 21.8 percent compared to tap water and combined water, respectively. In contrast, in the cement content of 350 kg.m-3, the highest compressive strength was obtained in samples made with tap water, briny groundwater and combined water, respectively, and the differences between them were statistically significant. The results showed that due to double and triple interaction of these three factors on compressive strength of cement pieces, which means different effects of water quality and application percent of zeolite on different content of cement, the choice of the best application level of zeolite and water type according to the cement content should be selected based on the mix design test in building site. However, using of briny grounwater and zeolite in the concrete mix design, especially in cement content of 350 kg.m-3, without significantly reducing the compressive strength of concrete and even significantly increase of this property in some treatments, is recommended.
Volume 19, Issue 3 (10-2019)
Abstract
Abstract:
Force-based seismic design, as the conventional earthquake resistant design philosophy, is going to be replaced with probabilistic performance-based design methodology. Through this method, induced damages against various levels of strong ground motions, play a dominant role. Seismic-induced damages are characterized by probabilistic damage functions, namely fragility curves. Fragility curves show the probability of exceeding damage levels (i.e. limit states) conditioned on strong ground motion intensities (i.e. Intensity Measures). Amongst well-known limit states (such as Immediate Occupancy, Life Safety and Collapse Prevention) for which the structure is to be checked, sidesway collapse limit state is of the greatest importance owing to the large amount of triggered losses during past earthquakes. Incremental Dynamic Analysis (IDA) method is the most popular method to achieve fragility curves for variuos limit states. By this methodology, the structure is affected by increasing levels of ensemble of strong ground motions. For each ground motion, the intensity which causes the instability of finite element model of the structure presents the collapse points. Fitting log-normal probability distribution to achieved intensities presents collapse fragility curve. The structure is to be checked against sidesway collapse in such a way that the probability of collapse for design-level seismic hazard is less than the pre-defined allowable probability.
Optimization of structures is aimed to present the topology, shape of structures and size structural sections in such that minimum target function (mostly structural weight) is achieved, while variuos design constraints are satisfied. Size optimization of structural members has been accomplished through previuos researches applying gravity and equivalent lateral forces. Besides to achieve optimum structures applying realistic effects of earthquakes, number of researches applied time history analysis of structures against one earthquake record or mean of number of earthquake records. To involve effects uncertainties regarding strong ground motions, probabilistic damage margins must be included in optimization constraints. To achieve this goal, in this paper, weight optimization of structres considering probabilistic constraints (represented by target collapse probability) is investigated. To achieve an efficient algorithm, the collapse fragility curve of structure is predicted by trained neural network. The network is trained based on incremental dynamic analysis of simulated models of samped structure. Besides probabilistic constraint regarding collapse probability margin, maximum normal stress and inter-story drift ratio (as deterministic constraints) are involved. Deterministic constraints are calculated by matrix analysis of the structure. Genetic algorithm is applied to solve the optimization problem. Finally, effects of target collapse probability on optimum weight are examined.
Achieved results show that the probabilistic constraint coverns the optimization problem if the target probability of collapse is less than 10%. Beyond this value, deterministic constraints, which are maximum normal stress and interstory drift ratio governs the optimum weight of the sampled structure.
Volume 19, Issue 3 (10-2019)
Abstract
With rapid rise in development of urban districts, a ferocious demand for water-collecting urban sewer systems is inevitable. In fact, flexible sewer collecting systems and drainage systems should be developed for controlling sewage and runoff, respectively. In the case of underground, conducting water flow properly through high vertical distances needs reliable criteria design for dissipating flow energy. Vortex structure is taken into account as one of the economical infrastructures which can be used to eradicate destructive impacts of inflow over a drop with invert elevation. In the current investigation, a physical model, made of Plexiglas segments, was set up to study hydraulic performance of vortex drop structure in terms of flow energy dissipation efficiency (FEDE). 144 experiments were conducted and analyzed by means of full factorial method (FFM). Results of dimensional analysis demonstrated that Froude number (Fr), ratio of drop total height to shaft diameter (L/D), and ratio of sump depth to shaft diameter (Hs/D) were considered effective variables on the FEDE. Hence, a regression based equation in form of a quadratic polynomial was proposed to estimate FEDE variable. Experiments aims were to investigate simultaneous effects of approach flow Fr, L/D, Hs/D on the FEDE. Results of experiments indicated that FEDE variable had downward trends with an increase in Fr variable and additionally, FEDE has gone through upward trends with an increase of L/D and Hs/D ratios. Increase in , which causes remarkable effect of wall friction on vortex flow, leads to increase in FEDE in the structure. Moreover, observations showed that decrease in inlet discharge for smaller Froude number results in more rotations of vortex flow in vertical shaft than flow with larger discharges for larger Froude number. This causes reduction of FEDE due to increase in inlet discharge. In addition, shown that in the structures with smaller L/D (L/D=10), the reduction effect of on the FEDE is more. With respect to positive effects of sump depth range (Hs/D=1-1.6) on FEDE and flow patterns observed in the entrance outlet tunnel, range (Hs/D=1-1.6) can be replaced by Hs/D range (0.7-1) proposed Zhao et al. [11]. In addition, the results showed that the interaction of and Hs/D on the FEDE in the structure is not significant.
For Q between 9.7 and 27.1 l/s, formation of hydraulic jump in tangential inlet was not occurred and flow was drained freely to drop shaft. Additionally, water surface in tangential inlet was lower than that of approach channel. In the outlet part of vortex structure, flow hitting the baffle leads to relatively significant increase in flow elevation top of the baffle in comparisons with other parts. Moreover, for constant values of Q and Hs/D ratio, flow elevation over the baffle has increased with an increase in L/D ratio, while for constant values of Q and L/D ratio, flow elevation has plummeted with an increase in Hs/D. Observations of experiments indicated that baffle-hitting flow accelerated without existence of sump at the base of drop shaft. Then caused to detaching flow and consequently occurrence of cavitation increased.