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Showing 8 results for Vaseghi


Volume 0, Issue 0 (in press 2024)
Abstract

Nowadays, the seismic performance-based design of structures has been widely noticed by the engineering community. So, different methods for performance-based design have been presented by different researchers. This attitude has been included in the design code and regulations for seismic design of new buildings and retrofit of existing buildings. The FEMA P-58 performance-based design method presented by the Pacific Earthquake Engineering Research (PEER) can quantify the consequences related to the seismic response of buildings. Therefore, using this method, the seismic performance of buildings can be directly evaluated. In addition, this performance-based design method can define simpler criteria such as repair cost, repair time, and casualties for seismic evaluation and decision-making process. The method is based on considering different sources of uncertainty in earthquake input and its intensity, structural response, associated damage, and repair cost, using the concepts of conditional probability and total probability theorem. In this method, the building is designed in such a way that it meets the expected and predetermined performance level in a specific level of seismic excitation. Since the performance levels of the building are determined based on the amount of damage caused to structural and non-structural members, one of the practical and effective ways to evaluate performance is to estimate the building repair cost. In the approach presented in FEMA P-58, the repair cost is defined in a probabilistic approach, as the cost needed to restore the damaged parts to their original state in the form of expected annual loss. In this research, first, three 4-, 12-, and 20-story office buildings with the lateral force resisting system of reinforced concrete special moment frames were selected in a high seismic risk area. Then, the nonlinear model of structures was provided in OpenSEES software. In order to reduce the computational cost and analysis time, the single-bay Substitute Frame model was used to simplify the multi-bay reinforced concrete moment frames. All four structures were subjected to Incremental Dynamic Analysis (IDA) for 30 earthquake records. A probabilistic relationship between the spectral acceleration of the earthquake and the main damage parameter (i.e. the inter-story drift), as well as the collapse fragility curve, was obtained. Then, the repair cost including the cost of repairing structural members as well as beams and columns, the cost of repairing non-structural members as well as partition and curtain walls, and the cost of replacing collapsed structures was calculated as expected annual loss. The results show that the repair costs at the Design-Based Earthquake (DBE) for 4-, 12-, and 20-story buildings are 3%, 2.5%, and 10% of the building replacement cost and at Maximum Credible Earthquake (MCE) are 22%, 23%, and 38% of the building replacement cost, respectively. In addition, in short buildings, most of the cost is caused by repairing structural and non-structural members, and in tall buildings, most of the cost is caused by replacing collapsed or severely damaged structures. Considering two nonstructural elements (i.e. partition and curtain walls) in repair cost, the analysis results show that the cost of repairing structural elements is more than the cost of repairing non-structural elements.
A.r. Panahi, A. Vaseghi,
Volume 10, Issue 3 (Summer 2019)
Abstract

All bacteria have many different secretion systems to transfer of their macromolecules to out. Currently, seven secretion systems have been identified. Transfer, tracing, and horizontal transmission of this gene groups, are many important in our understanding about these gene's application in bacteria and other substances. In this study, we examined Type III secretion system (T3SS) genes in Pseudomonas with using the bioinformatics software such as SeqWord Genome Browser in some databases for instants, ACLAME, Mobil Elements Genetic (MGEs), and PAthogenicity Islands Data Base (PAIDB). The results indicated that the T3SS genes transfers are observed with the percentage between 30% and 100%. Our findings also show the P. fluorescens bacterium has the most species with 15 transmitted genes. Bioinformatics predictors showed P. fluorescens F113 subtype with 11 genes had the highest transferability of T3SS cluster genes. The bacteria species such P. Fluorescens Pf-5, P. syringae pv. Glycinea, P. syringae pv. Aptata, P. syringae pv. Japonica, P. syringae pv. Pisi, P. aeruginosa UCBPP-PA14 show up about 100% of horizontal transfer from T3SS. Our results also indicated that T3SS, which are important in the bacteria disease, have the highest transmission rates. This study indicates can be showing the systematic transmission of disease from host and pathogen during the evolution.

Saeedeh Ghiasvand, Akbar Vaseghi, Firoozeh Alavian,
Volume 11, Issue 1 (Winter 2020)
Abstract

Escherichia coli is a Gram-negative bacterium, the second most common bacteria in the intestine and the main indicator of urban water pollution, is the most common cause of urinary tract infection and also is one of the main factors in food poisoning and diarrhea. Drug resistance of this bacterium to antibiotics is a global challenge. Horizontal gene transfer (HGT) is the movement of genetic material between unicellular and other gene transfer pathways which is an important factor in the evolution of many organisms, antibiotic resistance in bacteria, gene function. Antibiotic resistance in E. coli can be transferred to another species of bacteria through HGT mechanisms. Today, Bioinformatics methods have been used to understand of gene transfer from HGT mechanism. In this study, we used bioinformatics tools such as PredictBias, ACLAME, Mobil Genetic Elements (MGEs) PAI-ID, and Alien_Hunter in order to genes analysis that related from antibiotic resistance in E. coli. Bioinformatics and MIC assays result show that from 26 to 30 genes have been identified in all safthwers. Most of genes that identified show over 50 percent of GC content. put P gene with 178, blaCMY with 62, BlaTEM with 43, and aac-6 with 66 homology in the PredictBias website identified. Also in the ACLAME website, mob (A-C) and rep (A-C) gene family are highest number of horizontal gene transfer from infection bacteria strain. Those cluster genes are the highest resistant of laboratory tests which carries resistant genes such as  blaSHV and blaCHV on the blaCMY plasmid.       

Volume 11, Issue 4 (12-2011)
Abstract

Hydrodynamic pressure on the upstream face of the concrete dams under the effect of earthquake is one of the most important parameters, in planning dams' structure in earthquake zone. Because of the reservoir effect, dynamic analysis of concrete dams is more involved than other common structures. This problem is mostly sourced by the differences between reservoir water, dam body and foundation material behaviors. As a result, researches in this case must be able to evaluate the response of dam with consideration of dam’s interaction with reservoir and its foundation. This problem has been studied vastly by different researchers. The first research on the analysis of concrete gravity dam has been done by Westergaard in 1930 and hydrodynamic pressure on the dam face was obtained by some simplifications. There were a lot of other researches which studied the seismic behavior of the dam-reservoir system, including nonlinear behavior of the dam under pressure and also cavitation. In each research, different modeling methods are presented which are divided into two main groups. In first method which is called Eulerian method, pressure is the main unknown variable in reservoir nodes. In the second method that its main unknown variable is displacement of nodes is called lagrangian method. Each of the methods contain some advantageous and disadvantageous. The purpose of this paper is to evaluate possible advantages and disadvantages of both methods. Specifically, application of the above methods in the analysis of dam-foundationreservoir systems is leveraged to calculate the hydrodynamic pressure on dam faces. Within the frame work of dam- foundation-reservoir systems, dam displacement under earthquake for various dimensions and characteristics are also studied. To achieve this purpose, visual C#.NET 2003 computer programming language is used in this investigation that produces possibility of dynamic analysis of concrete dams under earthquake with system modeling by both methods. Nine node elements for reservoir and eight node elements for dam and foundation are used for both methods. Also newmark average acceleration method is used for solving dynamic’s equilibrium equation. Modares Civil Engineering Journal (M.C.E.L) Vol.11, No.4, Winter 2011 131 In this paper the response of the tallest, non-overflow monolith of Pine Flat dam in California, which is 122 m high, to horizontal and vertical component of earthquake is computed. A water depth of 116 m is considered in full reservoir condition, and the water has the following properties: unit mass,  1000 kg /m3 , bulk modulus, K  2.07*109 kg/m2 , and pressure wave velocity, w c 1440m/ s . The finite element model of reservoir consists of 12 isoparametric elements and it extends upstream a distance of 366 m, three times the dam height. The dam consists of 20 isoparametric elements. The concrete of dam has the unit mass of  2500kg /m3 , young’s modulus ofE  2.275*1010kg /m3, and poisson`s ratio of   0.25. The concrete of foundation has the unit mass of , young’s modulus ofE 4.45*1010 kg / m3 f  , and poisson`s ratio of  0.25 f  . The peak acceleration of S69E and vertical components are 0.18g and 0.1g, respectively. The results of both Lagrangian and Eulerian methods for Pine Flat dam are quantitatively evaluated and compared in different condition and following results are achieved: 1- In Lagrangian Method, there is only one variable in equilibrium equation and mass and stiffness matrixes are symmetric. But there is not such a condition in Eulerian method. Also, the numbers of unknown parameters are different in two methods. By considering these differentiations, needed time for analysis of Pine Flat Dam under Taft earthquake ,with mentioned characteristics, by Lagrangian method is 1.17 times more than needed time for Eulerian method. 2- The effect of material on reservoir's bottom in absorbing energy and `reducing system's response was considerable especially under vertical component of the earthquake. Results indicate that this case is not affected by reservoir modeling method. By applying this effect, the response will decrease about 15% under horizontal component and 60% under vertical component of the earthquake. 3- By evaluating the effect of reservoir bottom's slope, it is concluded that in the case of rigid foundation, the response by Lagarngian modeling is about 10% more than Eulerian one. With the increase of slope, the response will decrease under horizontal component of earthquake but it will decrease or increase about 13% under vertical component of the earthquake. In other words, reservoir bottom slope has little effect on response of the system under both vertical and horizontal component of earthquake. But this effect is not negligible. 4- It is included from the analyses that by decreasing the depth of reservoir the response will decease up to 50 percent under horizontal component of earthquake. This amount is 80 percent under vertical component. Also in the case of decreased depth, response of Lagarngian method is about 10% more than Eulerian method. 5-In all analysis, the assumption of rigid foundation results in greater answers than the cases of flexible foundation.

Volume 14, Issue 2 (7-2014)
Abstract

Abstract: Considering the seismicity of most of the areas in Iran, it is inevitable to confront the earthquake because of its major property and life damages. Therefore researchers put a great effort on designing and strengthening against earthquake. The researches conducted so far for improving the reinforced concrete structures using different types of steel braces and analytical studies and widespread experiments has been done for confronting destructive effects of earthquake on structures, results show the proper effectiveness of different mechanisms of inactive seismic control of structures as an efficient option for confronting the earthquake forces. Of different control methods, using friction damper could be counted as one of the best methods for improving the seismic behavior of current structures, as it uses a simple mechanism and doesn’t need specific materials or technology. By using friction dampers both the rigidity and the structure’s hysteresis energy loss ability is increased. These dampers by their inelastic behavior in different points of the structure cause the loss of incoming energy of earthquake. Also in high importance structures, by selecting the proper design parameters, it is possible to prevent the main structural members to enter the inelastic behavior limit which causes local damages to some parts of them or minimize that. This system was first introduced by Pall and March in 1982. The mechanism of this system is creating slippage friction surfaces at the intersection of braces. For building frames, these dampers could be used in crossed tension bracing, single diagonal bracing and Chevron bracing. The first model of pall friction damper was tested in chevron bracing against earthquake in Eaton Building in Canada. The purpose of this study is to investigate the role of Pall friction dampers in reducing structural response during the earthquake. Therefore, modeling of the damper is based on the model used by the Pall Corporation in Eaton Building. The functioning of this damper is by generating friction under lateral shear force which causes the movement of the damper and generation of slippage in it. Therefore, three concrete moment frames with 5, 8 and 10 stories, have been designed according to the Iranian National Codes. Using SAP2000, v14, several static nonlinear analyses were done to get the performance point of frames on the basis of the capacity spectrum method. Adding chevron braces to the mid span, the target displacement of frames were determined. Considering the fact that none of the braced moment frames satisfied the Life Safety criteria under Design Based Earthquake, Pall friction dampers have been added to the frames and static nonlinear analysis were done by several slip loads such as 1%, 10%, 25%, 50%, 75% and 100% of frame weights. Evaluation showed that in optimum slip Load, the performance level of the frames improves.

Volume 17, Issue 106 (December 2020)
Abstract

Jam is a product that uses a lot of sugar in its preparation, and this compound plays an important role in increasing the level of sugar. Since the increase in blood sugar is associated with diabetes and obesity, so reducing sugar consumption in this product can reduce the risk of these diseases which are caused by long-term use of this product. In this study, enzymatic invert sugar was used as a substitute for sugar in different ratios (0, 25, 50, 75 and 100%). Quince seed gum and pectin were also used as thickeners to improve the texture properties of jam. Measurement of acidity and pH, viscosity, brix, total sugar, reducing sugars, energy intake and sensory properties were measured. According to the results, with adding the gum and pectin, pH decreased, followed by acidity, brix, viscosity, reducing sugars, tissue hardness, yellowness and lightness index as well as sensory properties scores. Also, with increasing invert sugar, the acidity of samples increased, while brix and viscosity of samples decreased significantly (P˂0.05). But as the invert sugar concentration increased, the taste and color scores of the samples increased. The color score of the samples was significantly increased (P˂0.05) by adding quince seed gum. There was no statistically significant difference in odor of samples with increasing sugar replacement percentage (P≥0.05). In general, based on the results of physico-chemical and sensory tests, it can be said that jam samples containing 75% invert and 0.25% of gum to (treatment number 15) were the best samples with 15% fewer calories than control samples.

Volume 20, Issue 3 (10-2020)
Abstract

The present paper investigates and compares the crack propagation in concrete gravity dams using two models of linear fracture mechanics and plasticity damage concrete. The first model is based on linear concrete behavior using the extended finite element method without considering the effect of strain softening on the crack tip while the second model is based on the nonlinear concrete behavior and the strain softening in tension with damage parameter. According to two different algorithms and based on two models, several benchmark examples are reviewed and the results compared with those reported in the literature. Then, path of the crack growth in Koyna gravity dam due to a seismic excitation of Koyna earthquake in 1962 has been performed by considering the dam-reservoir interaction.
The results show that due to low compressive stresses during analysis of concrete gravity dams, consideration of compressive nonlinear behavior has no effect on crack initiation and almost is the same for two models. However because of crack opening and closing with tapping the crack faces together in extended finite element model, the compressive stress will be more than the allowable stress of concrete. Crack initiation at downstream and upstream face occurred at angle of 90 and zero degrees respectively, which in both models, the numerical results are in agreement with the experimental model.
The crack in the extended finite element model grows faster such that the crest block of dam in this model is separated from the dam body, earlier than the concrete plastic damage model. Also the values of dam crest displacement and hydrodynamic pressure in the reservoir in extended finite element model with linear elastic fracture mechanic are more than the other model, which can be attributed to the linear and nonlinear behavior of concrete in extended finite element and concrete plastic damage model respectively. In the extended finite element model, due to using linear fracture mechanic, the maximum principal stress in the cracked elements reaches the values greater than the maximum tensile strength, but in the concrete plastic damage model as soon as the stress reaches a tension limit value, elements are damaged and the stress is reduced. In both models, the crack located at the slope change area, propagates with the downward slope from downstream dam face and connects to the crack at upstream face which is growth horizontally.
Because of laboratory sample dimension and boundary condition of dam-reservoir compared with actual manner, neither of two crack profiles covered the experimental model, accurately. But it is shown that the crack profiles in the extended finite element model are more consistent with experimental results. Finally, the results show that the crack profile are slightly different in the two models because of quasi brittle behavior of the dam concrete, which can be attributed to the small fracture process zone of the crack tip in comparison with the dimension of the concrete gravity dams such that by removing strain softness part, the error in the amount of additional computation can be neglected.  
 

Volume 20, Issue 9 (September 2020)
Abstract

P91 steel is widely used in the construction of power plant components and the wider use of this steel is in the future planning of power plants in Iran. The preheating, the temperature control between the welding passes and the post-welding heat treatment, are required to obtain optimum toughness and creep resistance. Preheating, and most importantly post-heating are essential to prevent hydrogen remaining and the cracking problem. In this study, the effect of post-welding heat treatment (PWHT) and electrode drying on microstructure and mechanical properties of SMAW multi-pass weldment of P91 steel plate was studied by changing post-heating and baking processes. The optical microscope and FESEM microstructural studies, as well as ambient tensile tests, were done on a variety of different conditions from wet electrodes to post heated specimens that were used in order to evaluate the welding characteristics of SMAW process on the mentioned material. It was seen that utilizing wet electrodes with no immediate subsequent post-heating caused a noticeable decrease in tensile, and yield strength. On the other hand, post-heating treatment increases the number of precipitates in the weld metal and HAZ and the size of the primary austenite grains in the weld metal and HAZ becomes more homogeneous.


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