Amirkabir University of TechnologyAmirkabir Journal of Civil Engineering2588-297X51320190823Stability Anaysis of Real-time Hybrid Simulation for a Multi-story Structure Considering Time-delay of Hydrolic ActuatorStability Anaysis of Real-time Hybrid Simulation for a Multi-story Structure Considering Time-delay of Hydrolic Actuator391400291110.22060/ceej.2018.13547.5433FAMostafaNasiriGolpayegan universityAliSafiGolpayegan universityJournal Article20171015Real-Time Hybrid Simulation (RTHS) is a kind of simulation in which an experiment part of a structure tested within the real-time simulation of its other parts. In this article, a building with multi-story structure divided into numerical and experimental substructures and the vibration behavior of experiment story studied among the numerical simulation of other stories. To apply the effect of static and inertial forces produced by the other stories to the experimental story, an electrohydraulic actuator is used. The dynamic of the electrohydraulic actuator can be estimated by pure time-delay and this delay in the loop of simulation can reduce accuracy and cause the system instability. Therefore, Delayed Differential Equation (DDE) used to determine the critical time-delay depending on the system parameters. The results of simulation show the effect of non-dimensional parameters and time-delay in stability margin of hybrid simulation.Real-Time Hybrid Simulation (RTHS) is a kind of simulation in which an experiment part of a structure tested within the real-time simulation of its other parts. In this article, a building with multi-story structure divided into numerical and experimental substructures and the vibration behavior of experiment story studied among the numerical simulation of other stories. To apply the effect of static and inertial forces produced by the other stories to the experimental story, an electrohydraulic actuator is used. The dynamic of the electrohydraulic actuator can be estimated by pure time-delay and this delay in the loop of simulation can reduce accuracy and cause the system instability. Therefore, Delayed Differential Equation (DDE) used to determine the critical time-delay depending on the system parameters. The results of simulation show the effect of non-dimensional parameters and time-delay in stability margin of hybrid simulation.https://ceej.aut.ac.ir/article_2911_8137016bffcc3e843b4f3894bfce2d70.pdfAmirkabir University of TechnologyAmirkabir Journal of Civil Engineering2588-297X51320190823Effect of Near-Fault Earthquakes on the Sloshing Behavior of Concrete Rectangular Liquid Storage TanksEffect of Near-Fault Earthquakes on the Sloshing Behavior of Concrete Rectangular Liquid Storage Tanks401414290210.22060/ceej.2018.13553.5435FAMohammadrezaMardi PirsoltanFaculty of Engineering and Technology, Imam Khomeini International UniversityFouadKilaneheiFaculty of Engineering and Technology, Imam Khomeini International UniversityBenyaminMohebiFaculty of Engineering and Technology, Imam Khomeini International UniversityJournal Article20171015One of the most important components of water supply systems is the liquid storage tanks. During an earthquake, the interaction of fluid and structure in the liquid storage tanks and the sloshing phenomenon has a significant effect on the response values of the structure. Regarding the importance of the effects of near-fault earthquakes and their effect on seismic behavior and structures loads, in this study, the sloshing height and vibration of 2D concrete rectangular tanks under near- and far-field earthquakes was investigated using numerical methods. The effect of tank's dimensions, depth of water and ground motion characteristics on the maximum sloshing height was taken into account. Therefore, 9 tank models and 10 near- and far-field ground motion records were considered. The results indicated that the median values of maximum sloshing height in the near-field records are significantly higher than those related to far-field records. The average of increase of sloshing heights in tanks with lengths 20, 40 and 60 meters is 65, 77 and 100 percentage respectively. Also, with increase of fluid depth and tank width, the median of the maximum sloshing height increases and decreases respectively. In tanks, subjected to far- and near-field earthquakes, sloshing height had the highest correlation with Arias Intensity and PGV respectively. According to the results of this research, correction coefficients for the relations presented in the codes can be proposed to consider the effects of near-field earthquakes in calculating the maximum sloshing height.One of the most important components of water supply systems is the liquid storage tanks. During an earthquake, the interaction of fluid and structure in the liquid storage tanks and the sloshing phenomenon has a significant effect on the response values of the structure. Regarding the importance of the effects of near-fault earthquakes and their effect on seismic behavior and structures loads, in this study, the sloshing height and vibration of 2D concrete rectangular tanks under near- and far-field earthquakes was investigated using numerical methods. The effect of tank's dimensions, depth of water and ground motion characteristics on the maximum sloshing height was taken into account. Therefore, 9 tank models and 10 near- and far-field ground motion records were considered. The results indicated that the median values of maximum sloshing height in the near-field records are significantly higher than those related to far-field records. The average of increase of sloshing heights in tanks with lengths 20, 40 and 60 meters is 65, 77 and 100 percentage respectively. Also, with increase of fluid depth and tank width, the median of the maximum sloshing height increases and decreases respectively. In tanks, subjected to far- and near-field earthquakes, sloshing height had the highest correlation with Arias Intensity and PGV respectively. According to the results of this research, correction coefficients for the relations presented in the codes can be proposed to consider the effects of near-field earthquakes in calculating the maximum sloshing height.https://ceej.aut.ac.ir/article_2902_af6ad34ca7cf724170911d7a1fb66192.pdfAmirkabir University of TechnologyAmirkabir Journal of Civil Engineering2588-297X51320190823Experimental and FEM Study on Damaged Granitic Rock Using Second Rank Crack TensorExperimental and FEM Study on Damaged Granitic Rock Using Second Rank Crack Tensor415424276210.22060/ceej.2017.13575.5441FAKamranPanaghiTarbiat Modares UniversityAli AkbarGolshaniJournal Article20171023Any investigative approach towards rock behavior will necessitate inherent deficiencies such as pores and cracks to be taken into consideration. One of the methodologies employed to study cracked rock is to consider an equivalent continuum as for the domain with defects which will lend flexibility to experimental and numerical schemes due to its seamless effects on the constitutive relationships, hence reducing computational costs as well as experimental restraints in the laboratory. A case in point in such approach is the crack tensor model which is based upon the idea to represent cracks’ size, orientation, and number density as one single entity through which proper geometric characterization of the in-situ rock is carried out. Following the introduction of crack tensor concept and its application in the technical literature, the current work focuses on the determination of second rank crack tensor using P-wave velocity measurements on damaged granite. The benefit of such approach is emphasized via its role in boosting the degree of accuracy of the numerical analysis code developed in Matlab that implements different compliance matrices for four different stages of loading. The calculation results showed promising trends in agreement with those of the experimental data. Apparently, more experimental procedure is required to improve results’ accuracy in projects for which fulfilling more stringent regulatory requirements is a must.Any investigative approach towards rock behavior will necessitate inherent deficiencies such as pores and cracks to be taken into consideration. One of the methodologies employed to study cracked rock is to consider an equivalent continuum as for the domain with defects which will lend flexibility to experimental and numerical schemes due to its seamless effects on the constitutive relationships, hence reducing computational costs as well as experimental restraints in the laboratory. A case in point in such approach is the crack tensor model which is based upon the idea to represent cracks’ size, orientation, and number density as one single entity through which proper geometric characterization of the in-situ rock is carried out. Following the introduction of crack tensor concept and its application in the technical literature, the current work focuses on the determination of second rank crack tensor using P-wave velocity measurements on damaged granite. The benefit of such approach is emphasized via its role in boosting the degree of accuracy of the numerical analysis code developed in Matlab that implements different compliance matrices for four different stages of loading. The calculation results showed promising trends in agreement with those of the experimental data. Apparently, more experimental procedure is required to improve results’ accuracy in projects for which fulfilling more stringent regulatory requirements is a must.https://ceej.aut.ac.ir/article_2762_ab7bcba4a1e7d54c116a76a1595daffa.pdfAmirkabir University of TechnologyAmirkabir Journal of Civil Engineering2588-297X51320190823Investigate the Moisture Damage Mechanism in Asphalt Mixtures Using Thermodynamic
Parameters and Mixing DesignInvestigate the Moisture Damage Mechanism in Asphalt Mixtures Using Thermodynamic
Parameters and Mixing Design425436283210.22060/ceej.2018.13580.5440FAFereydoonMoghaddasnezhadAmirkabir University of Technology0000-0003-3830-4555MohyedinAsadiCivil،Islamic Azad University, Science and Research Branch, Tehran,IranJournal Article20171021 Moisture damage in asphalt mixtures is defined by loss of strength and durability due to water availability. The lack of correlation between the damage mechanism in the laboratory and the field conditions, the lack of measurement of the effective properties of the materials and their role, the lack of a corrective strategy and other shortcomings of existing laboratory methods to determine the moisture sensitivity has led researchers in recent years to consider providing methods based on effective parameters in damage events. Accordingly, this study is an attempt to provide a prediction model of moisture sensitivity using thermodynamic parameters and mixing design that can predict and analyze the asphalt mixture’s performance against moisture. 24 different combinations of asphalt mixtures have been investigated using three types of aggregate with different performance against moisture, two types of asphalt binder and three types of additives in this study. The surface free energy components of asphalt binder and aggregate were measured using a sticky drops and a general absorption device, respectively. To provide a prediction model for the performance of the moisture sensitivity of asphalt mixtures, the simulation of the conditions according to AASHTO T283 standard has been used and the indirect tensile resilient modulus test in dry and wet conditions has been performed. The results of this research indicate that the use of anti-stripping additives can generally improve the performance of asphalt mixtures against moisture, but the type and percentage of these additives should be determined according to the type of aggregate, the type of asphalt binder and the properties of the mixing plan for asphalt mixture. According to the proposed model, it can be said that the parameters of cohesive free energy, adhesive free energy of asphalt binder-aggregate in dry conditions, the coating of aggregates by asphalt binder, the specific surface area of the aggregates and the apparent thickness of the asphalt binder membrane on the aggregate surface directly and the energy released by the system during the occurrence of stripping, the percentage of saturation and the permeability of the asphalt mixture, inversely affect the asphalt mix’s strength against moisture damage Moisture damage in asphalt mixtures is defined by loss of strength and durability due to water availability. The lack of correlation between the damage mechanism in the laboratory and the field conditions, the lack of measurement of the effective properties of the materials and their role, the lack of a corrective strategy and other shortcomings of existing laboratory methods to determine the moisture sensitivity has led researchers in recent years to consider providing methods based on effective parameters in damage events. Accordingly, this study is an attempt to provide a prediction model of moisture sensitivity using thermodynamic parameters and mixing design that can predict and analyze the asphalt mixture’s performance against moisture. 24 different combinations of asphalt mixtures have been investigated using three types of aggregate with different performance against moisture, two types of asphalt binder and three types of additives in this study. The surface free energy components of asphalt binder and aggregate were measured using a sticky drops and a general absorption device, respectively. To provide a prediction model for the performance of the moisture sensitivity of asphalt mixtures, the simulation of the conditions according to AASHTO T283 standard has been used and the indirect tensile resilient modulus test in dry and wet conditions has been performed. The results of this research indicate that the use of anti-stripping additives can generally improve the performance of asphalt mixtures against moisture, but the type and percentage of these additives should be determined according to the type of aggregate, the type of asphalt binder and the properties of the mixing plan for asphalt mixture. According to the proposed model, it can be said that the parameters of cohesive free energy, adhesive free energy of asphalt binder-aggregate in dry conditions, the coating of aggregates by asphalt binder, the specific surface area of the aggregates and the apparent thickness of the asphalt binder membrane on the aggregate surface directly and the energy released by the system during the occurrence of stripping, the percentage of saturation and the permeability of the asphalt mixture, inversely affect the asphalt mix’s strength against moisture damagehttps://ceej.aut.ac.ir/article_2832_7ed85f94f2d41dbccdae063aa1e759b6.pdfAmirkabir University of TechnologyAmirkabir Journal of Civil Engineering2588-297X51320190823Performance of different seismic isolation systems in highway bridges subjected to
near-fault earthquakesPerformance of different seismic isolation systems in highway bridges subjected to
near-fault earthquakes437451283310.22060/ceej.2018.13537.5432FAAbbasKeramatiMSc. Students, Kharazmi UniversityGholamrezaNourikharazmi university, Tehran, IranJournal Article20171013Implementation of base isolation bearings is one of the effective methods to retrofit of bridges. In this study, performance of different seismic isolation systems under near-fault earthquakes is compared by applying nonlinear time history analysis of seismically isolated bridge by five different methods including Lead-Rubber (LRB), High Damping Rubber Bearing (HDRB), Single Friction Pendulum (SFP), Triple Friction Pendulum (TFP) and a typical bridge model by assuming a rigid connection between the deck and bridge piers is evaluated. Responses were estimated by performing nonlinear time history analyses by considering the main aspects of the simulation and by taking into account the nonlinear behavioral complexity of the base isolation bearing in OpenSees software. Results indicated that the frictional base isolations significantly reduce the stresses induced in the piers of bridge in comparison with the typical bridge model, and improve the seismic performance of the bridge substantially. The percentage of reduction for triple frictional pendulum and single frictional pendulum bearings reached 91% and 85%, respectivelyImplementation of base isolation bearings is one of the effective methods to retrofit of bridges. In this study, performance of different seismic isolation systems under near-fault earthquakes is compared by applying nonlinear time history analysis of seismically isolated bridge by five different methods including Lead-Rubber (LRB), High Damping Rubber Bearing (HDRB), Single Friction Pendulum (SFP), Triple Friction Pendulum (TFP) and a typical bridge model by assuming a rigid connection between the deck and bridge piers is evaluated. Responses were estimated by performing nonlinear time history analyses by considering the main aspects of the simulation and by taking into account the nonlinear behavioral complexity of the base isolation bearing in OpenSees software. Results indicated that the frictional base isolations significantly reduce the stresses induced in the piers of bridge in comparison with the typical bridge model, and improve the seismic performance of the bridge substantially. The percentage of reduction for triple frictional pendulum and single frictional pendulum bearings reached 91% and 85%, respectivelyhttps://ceej.aut.ac.ir/article_2833_d008eebd2132b0e31ddb47ac6b905a01.pdfAmirkabir University of TechnologyAmirkabir Journal of Civil Engineering2588-297X51320190823Project Risk Analysis Using an Integrated Probabilistic Beta-S Model and Multi-Parameter Copula FunctionProject Risk Analysis Using an Integrated Probabilistic Beta-S Model and Multi-Parameter Copula Function453464286410.22060/ceej.2018.13596.5443FAMehdiKhayyatiConstruction Engineering and Management, Science and Research Branch, Islamic Azad University, Tehran, IranAfshinFirouziJournal Article20171027One of the key attributes of any project is its time and cost constraints. Nowadays project-oriented organizations are looking for more advanced, accurate and efficient methods rather than traditional project management practices. Earned Value Management (EVM) is a well-accepted methodology to combine time, cost and scope of the projects reported in terms of Cost Performance Index (CPI) and Schedule Performance Index (SPI). However, a deterministic EVM cannot consider uncertainties of time and cost of activities of project and the correlation structure amongst them, which are inevitable and prevalent in any project. Therefore, an advanced probabilistic EVM is needed. A literature review reveals that there are only very limited studies in this area with different levels of complexity, maturity and limitations. In this study after defining the probability Number density functions, i.e., pdfs, of time and cost of every activity of project’s scheduled plan and their correlation structure, using Primavera Risk Analysis®, as a commercially available project risk analysis software, and Monte Carlo Simulation (MCS), in every iteration a time based cumulative cost of project, the socalled S-curve is created and normalized to be the inputs for curve fitting into a four parameter Beta-S function. Hence, for every iteration the corresponding values of these parameters can be calculated and the best performing marginal pdfs, be derived. In this paper in a novel approach, copula functions are employed to bind together these pdfs with a high level of efficiency and accuracy in terms of reliving the limitation of their belongingness to the same parametric group of marginal pdfs, e.g., multivariate Gaussian joint probability distribution. The proposed model collates all propagated uncertainties of the project activities in a single probabilistic closed form function. This copula function can be used in estimation of the performance indices of a probabilistic EVM and more importantly fed into a Bayesian updating scheme to estimate the project future performance more accurately.One of the key attributes of any project is its time and cost constraints. Nowadays project-oriented organizations are looking for more advanced, accurate and efficient methods rather than traditional project management practices. Earned Value Management (EVM) is a well-accepted methodology to combine time, cost and scope of the projects reported in terms of Cost Performance Index (CPI) and Schedule Performance Index (SPI). However, a deterministic EVM cannot consider uncertainties of time and cost of activities of project and the correlation structure amongst them, which are inevitable and prevalent in any project. Therefore, an advanced probabilistic EVM is needed. A literature review reveals that there are only very limited studies in this area with different levels of complexity, maturity and limitations. In this study after defining the probability Number density functions, i.e., pdfs, of time and cost of every activity of project’s scheduled plan and their correlation structure, using Primavera Risk Analysis®, as a commercially available project risk analysis software, and Monte Carlo Simulation (MCS), in every iteration a time based cumulative cost of project, the socalled S-curve is created and normalized to be the inputs for curve fitting into a four parameter Beta-S function. Hence, for every iteration the corresponding values of these parameters can be calculated and the best performing marginal pdfs, be derived. In this paper in a novel approach, copula functions are employed to bind together these pdfs with a high level of efficiency and accuracy in terms of reliving the limitation of their belongingness to the same parametric group of marginal pdfs, e.g., multivariate Gaussian joint probability distribution. The proposed model collates all propagated uncertainties of the project activities in a single probabilistic closed form function. This copula function can be used in estimation of the performance indices of a probabilistic EVM and more importantly fed into a Bayesian updating scheme to estimate the project future performance more accurately.https://ceej.aut.ac.ir/article_2864_0737e4ebf2ebaa9716bcd19440da0000.pdfAmirkabir University of TechnologyAmirkabir Journal of Civil Engineering2588-297X51320190823Effect of FRP Strips Configuration, Beam Dimensions and Amount of Tensile Rebars on Shear Capacity of Reinforced Concrete BeamsEffect of FRP Strips Configuration, Beam Dimensions and Amount of Tensile Rebars on Shear Capacity of Reinforced Concrete Beams465478287410.22060/ceej.2018.13619.5455FAMehrdadHejaziDepartment of Civil Engineering, Najafabad Branch, Islamic Azad University, Najafabad, IranMitraMohammadDept of Civil Engineering/Islamic Azad University, Najafabad BranchJournal Article20171101In this paper, the effect of the distance, number of layers and cross-sectional area of FRP strips, the amount of longitudinal rebars, dimensions of beam and compressive strength of concrete on shear capacity of reinforced concrete beams with rectangular crosssection stiffened by FRP strips under symmetrical concentrated loads using the finite element method has been studied. For this reason, the non-linear analysis of 101 reinforced beams has been performed for evaluation of the effect of the parameters on load capacity and mid-span deflection of the beams with and without strengthening. Obtained results indicate that for a constant concrete compressive strength, increasing the width and the number of layers of FRP strips increases the load capacity compared to the control beam. By changing the layout of reinforcing strips with irregular intervals along the beam, the load capacity increase is about 6% to 35%. Also, the increase of the amount of longitudinal rebars from Φ10 to Φ14 creasing the compressive strength of the concrete from 30 MPa to 50 MPa, and increasing the cross-sectional area of the beam from 150 × 300 mm to 150 × 400 mm in unstiffened beams, increase the load capacity by 31%, 23% and 55%, respectively.In this paper, the effect of the distance, number of layers and cross-sectional area of FRP strips, the amount of longitudinal rebars, dimensions of beam and compressive strength of concrete on shear capacity of reinforced concrete beams with rectangular crosssection stiffened by FRP strips under symmetrical concentrated loads using the finite element method has been studied. For this reason, the non-linear analysis of 101 reinforced beams has been performed for evaluation of the effect of the parameters on load capacity and mid-span deflection of the beams with and without strengthening. Obtained results indicate that for a constant concrete compressive strength, increasing the width and the number of layers of FRP strips increases the load capacity compared to the control beam. By changing the layout of reinforcing strips with irregular intervals along the beam, the load capacity increase is about 6% to 35%. Also, the increase of the amount of longitudinal rebars from Φ10 to Φ14 creasing the compressive strength of the concrete from 30 MPa to 50 MPa, and increasing the cross-sectional area of the beam from 150 × 300 mm to 150 × 400 mm in unstiffened beams, increase the load capacity by 31%, 23% and 55%, respectively.https://ceej.aut.ac.ir/article_2874_47e03423a3ea5b6a2480fdfd528eeacd.pdfAmirkabir University of TechnologyAmirkabir Journal of Civil Engineering2588-297X51320190823Damage detection in dolphin platform of a wharf by finite element model updatingDamage detection in dolphin platform of a wharf by finite element model updating479490300510.22060/ceej.2018.13674.5458FAMasoudPedramMaritime Engineering, Amirkabir University of TechnologyMohammad RezaKhedmatiFaculty Member
Amirkabir University of Technology0000-0001-6228-4916AkbarEsfandiariDepartment of maritime Engineering, Amirkabir University of TechnologyHosseinKazemNational Iranian Oil engineering and construction
Islamic Azad University-Tehran Jonoob branchJournal Article20171106In this paper, the performance of a damage detection method based on power spectral density (PSD) is numerically investigated on the dolphin platform of a wharf used for the unloading of merchant ships. In this numerical investigation damage is modeled as a percent reduction in stiffness of the elements. For this purpose, the finite-element model of the dolphin is made in the MATLAB software and the effect of surrounding water is considered as the added mass on the elements. To realise the performance of the method on the dolphin model, several assumed damage scenarios with different levels of damage in the structure, are considered. Furthermore, an approach for calculation of the spectral density of excitation using an approximate FRF is introduced. Results prove the success of the method in the identification of the parameters of a stiff coastal structure like a dolphin. Besides, the results from these investigations prove that the added mass significantly affects the damage detection results. The quality and accuracy of the numerical results prove the merits of damage detection by finite-element model updating in the frequency domain. The results of the present study urge the practical assessment of the performance of the method in the future.In this paper, the performance of a damage detection method based on power spectral density (PSD) is numerically investigated on the dolphin platform of a wharf used for the unloading of merchant ships. In this numerical investigation damage is modeled as a percent reduction in stiffness of the elements. For this purpose, the finite-element model of the dolphin is made in the MATLAB software and the effect of surrounding water is considered as the added mass on the elements. To realise the performance of the method on the dolphin model, several assumed damage scenarios with different levels of damage in the structure, are considered. Furthermore, an approach for calculation of the spectral density of excitation using an approximate FRF is introduced. Results prove the success of the method in the identification of the parameters of a stiff coastal structure like a dolphin. Besides, the results from these investigations prove that the added mass significantly affects the damage detection results. The quality and accuracy of the numerical results prove the merits of damage detection by finite-element model updating in the frequency domain. The results of the present study urge the practical assessment of the performance of the method in the future.https://ceej.aut.ac.ir/article_3005_f7611b91e304233f4af81e4450933786.pdfAmirkabir University of TechnologyAmirkabir Journal of Civil Engineering2588-297X51320190823Investigation of the performance of horizontal drains in increasing slope stability in intense rainfall conditions by numerical simulationInvestigation of the performance of horizontal drains in increasing slope stability in intense rainfall conditions by numerical simulation491502281410.22060/ceej.2018.13739.5468FAFarzinSalmasiDepartment of Science and Water Engineering, Faculty of Agriculture, University of Tabriz, Tabriz, Iran0000-0002-1627-8598AliHosseinzadeh DalirDepartment of Science and Water Engineering, Faculty of Agriculture, University of Tabriz, Tabriz, Iran0000-0003-2359-3921RezaNorouziDepartment of Science and Water Engineering, Faculty of Agriculture, University of Tabriz, Tabriz, Iran0000-0002-3756-8746Journal Article20171118 Every year heavy rainfalls cause many slope failures. In these rainfalls, the groundwater table increases that cause in increasing of pore water pressure and reduction of slope stability. Using of horizontal drains is an effective and economic method to control the slope stability in this condition. The purpose of this study is to investigate the performance of horizontal drains in increasing slope stability. For this purpose, the SEEP/W and SLOPE/W (subgroups of Geo-Studio software) were implemented. Results showed that increasing in the length, thickness, and number of horizontal drains causes increasing in slope stability during the heavy rainfalls and keep the slope more stable. In addition, installation of drains in the down part of slope is more effective than in the middle or top part of the slope. Relative drain length equal to 0.4 is proper for improving of slope stability. Increasing of drain thickness has more positive effect on slope stability than the drain length. Every year heavy rainfalls cause many slope failures. In these rainfalls, the groundwater table increases that cause in increasing of pore water pressure and reduction of slope stability. Using of horizontal drains is an effective and economic method to control the slope stability in this condition. The purpose of this study is to investigate the performance of horizontal drains in increasing slope stability. For this purpose, the SEEP/W and SLOPE/W (subgroups of Geo-Studio software) were implemented. Results showed that increasing in the length, thickness, and number of horizontal drains causes increasing in slope stability during the heavy rainfalls and keep the slope more stable. In addition, installation of drains in the down part of slope is more effective than in the middle or top part of the slope. Relative drain length equal to 0.4 is proper for improving of slope stability. Increasing of drain thickness has more positive effect on slope stability than the drain length.https://ceej.aut.ac.ir/article_2814_b8d9b115cb5a6fb2d45b821e148b2514.pdfAmirkabir University of TechnologyAmirkabir Journal of Civil Engineering2588-297X51320190823Detection of Damage in Simply-Supported Plates by Discrete Wavelet Transform of
Reconstructed Modal DataDetection of Damage in Simply-Supported Plates by Discrete Wavelet Transform of
Reconstructed Modal Data503522287910.22060/ceej.2018.13723.5465FAMiladPayestehMsc graduated in Civil Engineering, Jundi-Shapur University of Technology, Dezful, IranMortezaAghajan NashtaeeShahid Beheshti University0000-0003-0327-9054MohammadTaheri NasabFaculty of Civil Engineering, Jondi Shapur University of Technology, Dezful, Iran2372560001Seyed BahramBeheshti Avalfaculty member of shahid beheshti university of tehran iranJournal Article20171116Localized singularities caused by changes in the stiffness or mass of the damaged region cannot be simply visible through modal analysis results. However, the wavelet transform of input signal can identify the location of defects by sudden changes in the spatial variation of transformed response. The aim of this research is to present a new method for damage detection in a damaged plate. Therefore, a squarely steel plate with fixed support conditions is modeled, symmetrically. The proposed method in this study is capable to detect existing defects in plates with damage ratio of 3%. In this approach, based on symmetry or asymmetry of mode shapes, the value of each point of mode shape data is respectively subtracted from or added with its symmetric point. The results demonstrat that the small defects are detected with high resolution by employing reconstructed modal data in contrast to the original mode shape data. In addition, it has been shown that less-detailed measurement can still be used provided an interpolation is used to improve the accuracy of the crack detection and decrease financial cost of structural health monitoring projects.Localized singularities caused by changes in the stiffness or mass of the damaged region cannot be simply visible through modal analysis results. However, the wavelet transform of input signal can identify the location of defects by sudden changes in the spatial variation of transformed response. The aim of this research is to present a new method for damage detection in a damaged plate. Therefore, a squarely steel plate with fixed support conditions is modeled, symmetrically. The proposed method in this study is capable to detect existing defects in plates with damage ratio of 3%. In this approach, based on symmetry or asymmetry of mode shapes, the value of each point of mode shape data is respectively subtracted from or added with its symmetric point. The results demonstrat that the small defects are detected with high resolution by employing reconstructed modal data in contrast to the original mode shape data. In addition, it has been shown that less-detailed measurement can still be used provided an interpolation is used to improve the accuracy of the crack detection and decrease financial cost of structural health monitoring projects.https://ceej.aut.ac.ir/article_2879_5ffe8a0c4e592db292959f9bbe156fbf.pdfAmirkabir University of TechnologyAmirkabir Journal of Civil Engineering2588-297X51320190823The evaluation of concrete properties including zeolite and micro-nano bubble water in the chloride curing conditionThe evaluation of concrete properties including zeolite and micro-nano bubble water in the chloride curing condition523534271810.22060/ceej.2017.13603.5446FAMoeinKhoshrooM.Sc. Student, Construction and Engineering Management, Tehran University of kharazmiAliKatebiAssistant Professor, Faculty of Civil Engineering, Tehran University of kharazmiAli AkbarShirzadi JavidAssistant Professor, School of Civil Engineering, Iran University of Science and Technology, Tehran, Iran.Journal Article20171028The highest part of chemical ions present in the seawater is related to the chloride ion. In this research, the effect of chloride curing condition on the properties of concrete including zeolite as a mineral admixture and micro-nano bubble water is evaluated. Based on the experiments including X-ray diffraction, compressive strength, water absorption, chloride permeability and electrical resistance, it was determined that the addition of zeolite and micro-nano bubble water to the mixture improved the properties of concrete in the chloride conditions. Also results showed that the chloride curing condition causes an improvement in the properties of concrete at the age of 28 days due to the formation of Friedel salt. With increase in age of concrete up to 90 days and decomposition of Friedel salt composition in mixtures, the process of improvement is reduced. The highest effects on improving the mechanical properties and durability of concrete at the age of 28 days is related to the mixture including 15% zeolite and 100% micro-nano bubble water under chloride curing conditions. Improvement contents in the mentioned situation are 47, 78, 254, 84 and 49 percent corresponds to the compressive strength, tensile strength, electrical resistance, chloride permeability and water absorption test respectively.The highest part of chemical ions present in the seawater is related to the chloride ion. In this research, the effect of chloride curing condition on the properties of concrete including zeolite as a mineral admixture and micro-nano bubble water is evaluated. Based on the experiments including X-ray diffraction, compressive strength, water absorption, chloride permeability and electrical resistance, it was determined that the addition of zeolite and micro-nano bubble water to the mixture improved the properties of concrete in the chloride conditions. Also results showed that the chloride curing condition causes an improvement in the properties of concrete at the age of 28 days due to the formation of Friedel salt. With increase in age of concrete up to 90 days and decomposition of Friedel salt composition in mixtures, the process of improvement is reduced. The highest effects on improving the mechanical properties and durability of concrete at the age of 28 days is related to the mixture including 15% zeolite and 100% micro-nano bubble water under chloride curing conditions. Improvement contents in the mentioned situation are 47, 78, 254, 84 and 49 percent corresponds to the compressive strength, tensile strength, electrical resistance, chloride permeability and water absorption test respectively.https://ceej.aut.ac.ir/article_2718_f3eb6c3a27882b0f8d5bdfb45119080a.pdfAmirkabir University of TechnologyAmirkabir Journal of Civil Engineering2588-297X51320190823Equilibrium and Kinetics Investigations on Sorption of C.I. Basic Red 14 onto Low-cost FeldsparEquilibrium and Kinetics Investigations on Sorption of C.I. Basic Red 14 onto Low-cost Feldspar535546287510.22060/ceej.2018.13770.5475FAHosseinKetabiTextile Engineering Department, Faculty of Engineering, University of Guilan, Rasht, IranLeilaMivehiTextile Engineering Department, Faculty of Engineering, University of Guilan, Rasht, Iran0000-0003-2336-6067Journal Article20171125Feldspar as a low-cost mineral adsorbent based on silica was used to removal a cationic dye, C.I. Basic Red 14 (Brilliant red 4G), from aqueous solution. The adsorbent was characterized using Scanning Electron Microscopy (SEM), X-ray Fluorescence (XRF) and Fourier Transform Infra-Red spectroscopy (FTIR). The effect of some parameters such as the amount of adsorbent, contact time, the initial concentration of dye, initial pH and electrolyte on dye removal was investigated. Results showed that dye removal increased by increasing pH; contact time and adsorbent dosage, whereas decreased by increasing the dye concentration. Also, the addition of electrolyte caused a negligible decreasing in dye removal. It took about 1 hour to equilibrium the feldspar with C.I. Basic red 14 and dye removal efficiency was 96%. So, feldspar is a suitable and powerful absorbent for removal of cationic dye from aqueous solutions. Equilibrium isotherms were analyzed by Langmuir, Freundlich, Temkin, Redlich-Peterson, and Dubinin–Radushkevich adsorption models and found that the experimental data were correlated reasonably well with Freundlich isotherm. The adsorption kinetics was studied by using pseudofirst-order, pseudo-second-order, and intra-particle diffusion models and realized the adsorption of C.I. Basic red 14 on feldspar followed the pseudo-second-order equation which indicates to chemical sorption.Feldspar as a low-cost mineral adsorbent based on silica was used to removal a cationic dye, C.I. Basic Red 14 (Brilliant red 4G), from aqueous solution. The adsorbent was characterized using Scanning Electron Microscopy (SEM), X-ray Fluorescence (XRF) and Fourier Transform Infra-Red spectroscopy (FTIR). The effect of some parameters such as the amount of adsorbent, contact time, the initial concentration of dye, initial pH and electrolyte on dye removal was investigated. Results showed that dye removal increased by increasing pH; contact time and adsorbent dosage, whereas decreased by increasing the dye concentration. Also, the addition of electrolyte caused a negligible decreasing in dye removal. It took about 1 hour to equilibrium the feldspar with C.I. Basic red 14 and dye removal efficiency was 96%. So, feldspar is a suitable and powerful absorbent for removal of cationic dye from aqueous solutions. Equilibrium isotherms were analyzed by Langmuir, Freundlich, Temkin, Redlich-Peterson, and Dubinin–Radushkevich adsorption models and found that the experimental data were correlated reasonably well with Freundlich isotherm. The adsorption kinetics was studied by using pseudofirst-order, pseudo-second-order, and intra-particle diffusion models and realized the adsorption of C.I. Basic red 14 on feldspar followed the pseudo-second-order equation which indicates to chemical sorption.https://ceej.aut.ac.ir/article_2875_c1912010f32784d3f7e1ad3472681502.pdfAmirkabir University of TechnologyAmirkabir Journal of Civil Engineering2588-297X51320190823Leak detection, experimental and theoretical comparison of characteristics of transient flow in polyethylene pipelinesLeak detection, experimental and theoretical comparison of characteristics of transient flow in polyethylene pipelines547556276710.22060/ceej.2017.13539.5438FAMostafaMirzaie JeshniDepartment of Water Sciences Engineering, Shahid Chamran UniversityManoochehrFathi-MoghadamDepartment of Water Sciences Engineering, Shahid Chamran UniversityAlirezaSabet-imaniDepartment of Water Sciences Engineering, Shahid Chamran UniversityAsgharAkbariDepartment of Water Sciences Engineering, Shahid Chamran UniversityJournal Article20171019Polyethylene pipes are widely used in pressurized water systems. In the design and interpretation of the ram-trapped signal for diagnostic purposes, viscoelastic behavior of polyethylene tubes should be taken into account. The aim of this study is to detect leakage, and experimental and theoretical comparison of pressure wave velocity and over pressure of transient flow in polyethylene pipes with different Reynolds number. To achieve the objectives of this paper, a physical model was developed in laboratory of the Faculty of Water Sciences Engineering of Shahid Chamran University of Ahwaz and developed two different models of control and a leakage system was and were conducted a number of water-hammer tests. The leakage accuracy in this model increased with increase of Reynolds number. The highest and the lowest percent of the relative error for computational and experimental leakage were estimated 48.8% and 2.02% through a leak hole of 5 mm for experiments with Reynolds numbers of 1283 and 12974, respectively. Also, this inaccurate study shows the relationship between the theory of compressive velocity and overpressure in the polyethylene transfer pipes, so that the compressive velocity obtained from theoretical relationships is less than its actual value, as well as the relative error of the overpressure in leakage experiments Increasing the Reynolds number increases between the amount of the laboratory and the theory.Polyethylene pipes are widely used in pressurized water systems. In the design and interpretation of the ram-trapped signal for diagnostic purposes, viscoelastic behavior of polyethylene tubes should be taken into account. The aim of this study is to detect leakage, and experimental and theoretical comparison of pressure wave velocity and over pressure of transient flow in polyethylene pipes with different Reynolds number. To achieve the objectives of this paper, a physical model was developed in laboratory of the Faculty of Water Sciences Engineering of Shahid Chamran University of Ahwaz and developed two different models of control and a leakage system was and were conducted a number of water-hammer tests. The leakage accuracy in this model increased with increase of Reynolds number. The highest and the lowest percent of the relative error for computational and experimental leakage were estimated 48.8% and 2.02% through a leak hole of 5 mm for experiments with Reynolds numbers of 1283 and 12974, respectively. Also, this inaccurate study shows the relationship between the theory of compressive velocity and overpressure in the polyethylene transfer pipes, so that the compressive velocity obtained from theoretical relationships is less than its actual value, as well as the relative error of the overpressure in leakage experiments Increasing the Reynolds number increases between the amount of the laboratory and the theory.https://ceej.aut.ac.ir/article_2767_75aca978a8c3eb4a69c65f7fd3579643.pdfAmirkabir University of TechnologyAmirkabir Journal of Civil Engineering2588-297X51320190823Numerical and Experimental Studies of Seismic in-Soil Isolation of MSW Landfill by Geosynthetic Liners: Case Study of Kahrizak Landfill,Tehran, IranNumerical and Experimental Studies of Seismic in-Soil Isolation of MSW Landfill by Geosynthetic Liners: Case Study of Kahrizak Landfill,Tehran, Iran557574301410.22060/ceej.2018.13759.5471FAVahidMirhajiDepartment of Civil Engineering, Science and Research Branch, Islamic Azad University, Tehran, IranYaserJafarianGeotechnical Engineering Research Center, International Institute of Earthquake Engineering and Seismology, Tehran, IranMohamad HasanBaziarSchool of Civil Engineering, Iran University of Science and Technology, Tehran, IranMohammad KazemJafariGeotechnical Engineering Research Center, International Institute of Earthquake Engineering and Seismology, Tehran, IranJournal Article20171122The purpose of municipal solid waste landfills (MSWLF) is to dispose non-recyclable materials, gas extraction, composting, and controlling of pollutants that threaten human health and the environment, and finally providing useful areas after filling. Since Iran is located on the seismic belt and has experienced some high intense earthquake, the study of the Tehran’s MSWLF landfill known as the Kahrizak landfill is important. Seismic loads may damage MSWLF through the relative movements within the waste, bottom lining system, cover system, foundation, and interfaces. The smooth synthetic materials might be placed beneath the structures to provide seismic protection by absorbing the imparted energy of earthquakes through the sliding mechanism. In the present study, experimental investigations were conducted in order to evaluate role of in-soil base isolation on seismic response of the Kahrizak MSW landfill. Shaking table tests were conducted on the MSW embankment isolated by semi-elliptic shaped liners and subjected to harmonic sinusoidal base excitations. Furthermore, the behavior of the physical shaking table model was investigated by numerical modeling. The results of the isolated and non-isolated cases are compared in terms of permanent displacement and seismic response. In this study, a good agreement was found between the results of the physical model and the large scale numerical model. Studies have shown that the use of a composite liner system with a further reduction in the friction coefficient results in a significant reduction in the amount of acceleration and displacement, and can protect the structure in seismic conditions. This method did not show a significant effect on the landfill settlement. The efficiency of this technique increases with increasing the amplitude of input motion employed in the current study. It was also observed that employing flat liner leads the movement of the ridge to the sides; and the concave liner prevents the wedge to move excessively.The purpose of municipal solid waste landfills (MSWLF) is to dispose non-recyclable materials, gas extraction, composting, and controlling of pollutants that threaten human health and the environment, and finally providing useful areas after filling. Since Iran is located on the seismic belt and has experienced some high intense earthquake, the study of the Tehran’s MSWLF landfill known as the Kahrizak landfill is important. Seismic loads may damage MSWLF through the relative movements within the waste, bottom lining system, cover system, foundation, and interfaces. The smooth synthetic materials might be placed beneath the structures to provide seismic protection by absorbing the imparted energy of earthquakes through the sliding mechanism. In the present study, experimental investigations were conducted in order to evaluate role of in-soil base isolation on seismic response of the Kahrizak MSW landfill. Shaking table tests were conducted on the MSW embankment isolated by semi-elliptic shaped liners and subjected to harmonic sinusoidal base excitations. Furthermore, the behavior of the physical shaking table model was investigated by numerical modeling. The results of the isolated and non-isolated cases are compared in terms of permanent displacement and seismic response. In this study, a good agreement was found between the results of the physical model and the large scale numerical model. Studies have shown that the use of a composite liner system with a further reduction in the friction coefficient results in a significant reduction in the amount of acceleration and displacement, and can protect the structure in seismic conditions. This method did not show a significant effect on the landfill settlement. The efficiency of this technique increases with increasing the amplitude of input motion employed in the current study. It was also observed that employing flat liner leads the movement of the ridge to the sides; and the concave liner prevents the wedge to move excessively.https://ceej.aut.ac.ir/article_3014_e4254d068f14b853da2864261641e276.pdfAmirkabir University of TechnologyAmirkabir Journal of Civil Engineering2588-297X51320190823Adsorption modeling and optimization of crystal violet a cationic dye in batch reactorAdsorption modeling and optimization of crystal violet a cationic dye in batch reactor575584281310.22060/ceej.2018.13445.5410FAHabibKoulivanddeportment of environmental technology, environmental science research institute, shahid beheshti university, Tehran, IranAfsanehShahbaziProf., Environmental Sciences Research Institute, Shahid Beheshti University, G.C., Tehran, IranJournal Article20170919Graphene oxide nano-sheets were synthesized using modified Hummer’s method and characterized using Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), and Fourier Transform Infra-Red (FTIR) analyses. Response surface methodology (RSM) was used to optimize the effects of the effective factors including pH (4-9), adsorbent dosage (0.05-0.4 g/L), initial dye concentration (50-400 mg/L), and temperature (10-40 C°) in batch adsorption reactor. The adsorption capacity of graphene oxide and removal percentage of crystal violet in the optimum condition (pH of 7.4, the adsorbent dosage of 0.19 g/L, the initial concentration of 100 mg/L, and temperature of 30.4 C°) were predicted by the polynomial regression model to be 474 mg/g and 90%, respectively. Dye initial concentration and the adsorbent dosage with 51.6 and 41.7% respectively, showed the most percentage of contribution among the effective factors. Adsorption kinetic was investigated using pseudo-first order, pseudo-second order, and intraparticle diffusion kinetic models. Adsorption isotherm also was studied using Freundlich and Langmuir isotherm models. Results demonstrated the high correlation of adsorption kinetic and isotherm with pseudo-second order and Langmuir models respectively. In addition, the thermodynamic study indicated the endothermic and spontaneous nature of adsorption.Graphene oxide nano-sheets were synthesized using modified Hummer’s method and characterized using Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), and Fourier Transform Infra-Red (FTIR) analyses. Response surface methodology (RSM) was used to optimize the effects of the effective factors including pH (4-9), adsorbent dosage (0.05-0.4 g/L), initial dye concentration (50-400 mg/L), and temperature (10-40 C°) in batch adsorption reactor. The adsorption capacity of graphene oxide and removal percentage of crystal violet in the optimum condition (pH of 7.4, the adsorbent dosage of 0.19 g/L, the initial concentration of 100 mg/L, and temperature of 30.4 C°) were predicted by the polynomial regression model to be 474 mg/g and 90%, respectively. Dye initial concentration and the adsorbent dosage with 51.6 and 41.7% respectively, showed the most percentage of contribution among the effective factors. Adsorption kinetic was investigated using pseudo-first order, pseudo-second order, and intraparticle diffusion kinetic models. Adsorption isotherm also was studied using Freundlich and Langmuir isotherm models. Results demonstrated the high correlation of adsorption kinetic and isotherm with pseudo-second order and Langmuir models respectively. In addition, the thermodynamic study indicated the endothermic and spontaneous nature of adsorption.https://ceej.aut.ac.ir/article_2813_4771987e570b5aacd54e1b39291392df.pdfAmirkabir University of TechnologyAmirkabir Journal of Civil Engineering2588-297X51320190823Probabilistic Seismic Vulnerability assessment of RC Frame Structures Retrofitted with Steel JacketingProbabilistic Seismic Vulnerability assessment of RC Frame Structures Retrofitted with Steel Jacketing585598280910.22060/ceej.2018.13692.5459FAHosseinPahlavanAssisstant Professor of Earthquake Engineering, Shahrood University of Technology0000-0002-7016-9683AliNaseriPh.D. Candidate of Structural Engineering, Babol Noshirvani University of TechnologyArminEinolahiMsc. student of Structural Engineering, University of Pardisan, Mazandaran.Journal Article20171109A majority of Iranian residential buildings have Reinforced Concrete (RC) frame structures with intermediate ductility. Recent earthquakes have revealed major seismic deficiencies in these buildings, some of which led to catastrophic collapses and significant death tolls. Causes for the unsatisfactory performance include the absence of special seismic detailing of key structural elements, inadequate material and construction quality. Based on an extensive field investigation done by the authors on the short, mid-rise and high-rise Northern Iranian as-built structures having RC frames, in this study, reduced strength of concrete and also insufficient overlap length of column’s longitudinal bars are considered as common structural deficiencies and then by considering probable uncertainties such as material and earthquake uncertainty, the seismic performance of considered buildings are developed via fragility curves based on probabilistic method. For generation of seismic fragility curves for as built and also retrofitted models, 3 dimensional analytical models analyzed based on Incremental Dynamic Analysis (IDA) in OpenSEES. The demand statistics in terms of maximum inter– story drift ratio are obtained for 20 sets of ground motion records and the capacity is determined according to the HAZUS-MH limit states and finally the corresponding fragility curves for four damage states are developed for as built and retrofitted models. The results represent the effect of the story numbers, structural deficiency and implemented retrofit strategy on the seismic vulnerability of this subclass of structures.A majority of Iranian residential buildings have Reinforced Concrete (RC) frame structures with intermediate ductility. Recent earthquakes have revealed major seismic deficiencies in these buildings, some of which led to catastrophic collapses and significant death tolls. Causes for the unsatisfactory performance include the absence of special seismic detailing of key structural elements, inadequate material and construction quality. Based on an extensive field investigation done by the authors on the short, mid-rise and high-rise Northern Iranian as-built structures having RC frames, in this study, reduced strength of concrete and also insufficient overlap length of column’s longitudinal bars are considered as common structural deficiencies and then by considering probable uncertainties such as material and earthquake uncertainty, the seismic performance of considered buildings are developed via fragility curves based on probabilistic method. For generation of seismic fragility curves for as built and also retrofitted models, 3 dimensional analytical models analyzed based on Incremental Dynamic Analysis (IDA) in OpenSEES. The demand statistics in terms of maximum inter– story drift ratio are obtained for 20 sets of ground motion records and the capacity is determined according to the HAZUS-MH limit states and finally the corresponding fragility curves for four damage states are developed for as built and retrofitted models. The results represent the effect of the story numbers, structural deficiency and implemented retrofit strategy on the seismic vulnerability of this subclass of structures.https://ceej.aut.ac.ir/article_2809_08d76cdaa4a464c3e4db5a255c97363a.pdfAmirkabir University of TechnologyAmirkabir Journal of Civil Engineering2588-297X51320190823Identification and Prioritization the Risks of Green Building Projects Based on the
Combination of FANP and FDEMATEL: (Case study: Savadkooh County)Identification and Prioritization the Risks of Green Building Projects Based on the
Combination of FANP and FDEMATEL: (Case study: Savadkooh County)599616276810.22060/ceej.2017.13302.5398FAJavadGhaobadiDepartment of Industrial Engineering, Mazandaran University of Science and Technology, Babol, IranJavadRezaeianIndustrial Engineering, Mazandaran University of Science and Technology, Baboil, IranMostafaHaji Aghaei KeshteliDepartment of Industrial Engineering, University of Science and Technolgy of MazandarnJournal Article20170907Green buildings are consistent objects which consider environment issues and natural resources throughout their life cycle. The risks on green construction projects reduce the accuracy of the estimation of the projects objectives and reduce the efficiency of green building projects. Therefore, identification and prioritization of risks can play a significant role in the success of green construction projects. In this research, a comprehensive model of all criteria and indicators of the risks for green construction projects are presentedAt first step, the indicators have been evaluated and ranked first by fuzzy Delphi technique by the identification and verification experts, and then by combining the results of the network analysis process and the DEMATEL technique in fuzzy conditions. Finally, the final ranking of the indicators is done according to the results obtained in the super decision software. in fuzzy conditions to rank and evaluate the causal relationships between the factors and ultimately final prioritizing green building risk indicators have been done in terms of the results of the initial steps using the fuzzy Analysis Network Process FANP and DEMATEL technique. The results of the research showed that the risks associated with poor quality of materials and inappropriate equipment are very important and the lack of scale for the cost of activities has the least importance.Green buildings are consistent objects which consider environment issues and natural resources throughout their life cycle. The risks on green construction projects reduce the accuracy of the estimation of the projects objectives and reduce the efficiency of green building projects. Therefore, identification and prioritization of risks can play a significant role in the success of green construction projects. In this research, a comprehensive model of all criteria and indicators of the risks for green construction projects are presentedAt first step, the indicators have been evaluated and ranked first by fuzzy Delphi technique by the identification and verification experts, and then by combining the results of the network analysis process and the DEMATEL technique in fuzzy conditions. Finally, the final ranking of the indicators is done according to the results obtained in the super decision software. in fuzzy conditions to rank and evaluate the causal relationships between the factors and ultimately final prioritizing green building risk indicators have been done in terms of the results of the initial steps using the fuzzy Analysis Network Process FANP and DEMATEL technique. The results of the research showed that the risks associated with poor quality of materials and inappropriate equipment are very important and the lack of scale for the cost of activities has the least importance.https://ceej.aut.ac.ir/article_2768_44dd71018a7d2d30335bc32f58656c97.pdf