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List of Articles
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Open Access Article
1 - Assessment of RC frames with different ductility using endurance time analysis
Ali Sadeghi Esmaeil MousapoorEndurance time method is a new method of seismic analysis in which the structure is subjected to an increased dynamic excitation whose intensity gradually enhances over time. The response of structure is investigated over time and based on the response corresponding to MoreEndurance time method is a new method of seismic analysis in which the structure is subjected to an increased dynamic excitation whose intensity gradually enhances over time. The response of structure is investigated over time and based on the response corresponding to different levels of excitation intensity, strengths, weaknesses, and performance of the structure were evaluated. In this research, according to the rules of regulations, two 5- and 8-storey buildings were linearly analyzed and designed applying ETABS software and with medium and special ductility. Then, a sample frame was separated from the structure and overall, four concrete frames of 5 and 8 floors with medium and special ductility were analyzed by endurance time method. The ETA20-KD durability stimulation function was applied to evaluate these frames. Nonlinear hinges of structural components were defined according to instruction for seismic rehabilitation of existing buildings No. 360. The results of this study presented that concrete frames with special ductility have less damage and longer endurance time than those with medium ductility. So that the failure of a 5-storey building with medium and special ductility occurred at 11.64 and 20 seconds, respectively, and the failure of an 8-storey building with medium and special ductility took place at 10.21 and 13.08 seconds, respectively Manuscript profile -
Open Access Article
2 - The Effect of Earthquake Vertical Component on Structures with Mass and Stiffness Irregularities in Height
Masoud Jahanpanah Hossein SohrabzadehThe earthquake vertical component and its influence on the analysis of buildings have long been considered by researchers and design engineers. However, so far, the considerations resulting from the effect of the vertical component of the earthquake in the design of bui MoreThe earthquake vertical component and its influence on the analysis of buildings have long been considered by researchers and design engineers. However, so far, the considerations resulting from the effect of the vertical component of the earthquake in the design of buildings (unless partially in beams) with irregular mass and stiffness in height have not been studied. For this reason, this research is important in order to answer the question regarding impact of earthquake vertical component on buildings, which have irregularity in mass and stiffness in the height. So far, most of the research about the buildings with mass and hardness irregularities in the height has been studied only with respect to the influence of earthquake with horizontal component. However, the 2800 standard does not comprehensively predict the effect of the vertical seismic component on seismic loading, and the only effect of the vertical seismic component according to the 2800 standard is significant for the earthquake prone areas, cantilever beams, beams with a span of more than fifteen meters and beams with remarkable concentrated vertical load. According to the above cases to investigate the influence of seismic vertical component in the buildings with mass and hardness irregularity in the height, three 10-floor structures with steel curving frames, each in a different form on sixth floor, with mass and hardness irregularity, were analyzed. This irregularity is observed in standard 2800 boundary. The structures are then subjected to nonlinear dynamic analysis under five earthquake groups with PGA (Earth Acceleration Peak) values of 0.2g, 0.35g, 0.5g, 0.65g and 0.8g. It should be noted that each group has seven earthquakes that have three accelerometers (two horizontal components and one vertical component). Then, the maximum results of each earthquake are obtained and these results are averaged for each separate group and the obtained result is considered as the final result. The results of nonlinear dynamic analysis presented that through the interference of the vertical seismic component, the amount of drift ratio in the floor containing mass and stiffness irregularity, increased by about 5 to 25 percent and the amount of axial force of the column increased by about 5 to 30 percent. Manuscript profile -
Open Access Article
3 - Extension of Genetic Algorithm Relationships for Estimating the Global Ductility of EBFs under Near-fault Pulse-type Earthquake
Seyed Abdonnabi Razavi Navid Siahpolo Mehdi Mahdavi Adeli Mohamad Bahmani Seyed Afshin Mohebi Bahram BarriDuctility of the structure is the ability to withstand trans-elastic deformations of the structure without a significant drop in strength. Examining the results of past earthquakes and the damage to structures makes its ductility and supply in the structure an important MoreDuctility of the structure is the ability to withstand trans-elastic deformations of the structure without a significant drop in strength. Examining the results of past earthquakes and the damage to structures makes its ductility and supply in the structure an important issue. In this paper, in order to take advantage of the strengths of the design method based on the performance and computational ease of force design methods, frames with 3, 6, 9, 12, 15 and 20 floors have been considered. Then, a large database consisting of 12960 data was generated and designed with the purpose of 3 types of column stiffness and 3 degrees of bracing thinness and analyzed against 20 earthquakes near pulsed faults for 4 different performance levels. Finally, using the genetic algorithm, the experimental relationships corresponding to the coefficients of behavior, global ductility and link beam ductility are presented. The proposed relationships are influenced by geometric characteristics such as the number of floors, the stiffness ratio of the columns, the slenderness of the braces, the length of link beam, and the ductility levels. The results of seismic design using the proposed relationships on structures outside the range of the defined database, in comparison with the force methods, show the accuracy of this method in estimating the seismic needs of divergent bracing frames. It can be concluded that based on the production relations of the database, and the validation of the production relations, the results of the structural design by the resulting relations have an acceptable validity. Manuscript profile -
Open Access Article
4 - Evaluation of Rheological and Mechanical Properties of Lightweight Concrete Containing Different Percentages of Polypropylene and Zeolite Fibers
Abdolkarim Abbasi Dezfouli Rezbeh AghajaryLightweight concrete is one of the most important and efficient materials in the modern construction industry and has a variety of applications. Proper application of lightweight concrete can have many positive influences on the construction process of concrete structur MoreLightweight concrete is one of the most important and efficient materials in the modern construction industry and has a variety of applications. Proper application of lightweight concrete can have many positive influences on the construction process of concrete structures. The possibility of application in the most geographical regions, utility of natural and cheap materials, high speed, low cost compared to the large volume of operations and its ductility due to the geometric shapes of the design, good performance and very high resistance, resistant to compressive forces and tensile strength, energy absorption and cracking stability are the prominent features of lightweight structural concretes. The main purpose of this research was to investigate the rheological and mechanical properties of the lightweight concrete containing different percentages of zeolite and polypropylene fiber separately. In this research, applying laboratory method, the rheological properties of fresh lightweight concrete (soft concrete) and the mechanical properties of hardened lightweight concrete at the ages of 7 and 28 days have been evaluated. According to ASTMC 39 standard, two samples of lightweight concrete without zeolite and polypropylene at the ages of 7 and 28 days have been prepared and mechanically evaluated. Then, in continuation of preparing of the light concrete samples prepared based on ASTMC 39 standard, three mixing designs with different percentages of polypropylene fibers (0.9, 1 and 1.1%) and 3 mixing designs with different percentages of zeolite (5, 10 and 15%) , at the mentioned ages were examined and compared with the base samples in the laboratory, which resulted in the following findings: Lightweight concrete samples containing zeolite had a higher electrical resistance than lightweight concrete samples containing polypropylene and the highest compressive strength was related to lightweight concrete samples containing 15% zeolite. This is equivalent to 400.75 kg / cm3 at the age of 28 days. Manuscript profile -
Open Access Article
5 - Identification of Location and Severity of Damages in the Offshore wind Turbine Tripod Platform by Improved Modal Strain Energy Method
Seyed Reza Samaei Madjid Ghodsi Hassanabad amin karimpor zahraeiTruss structures are one of the most common offshore structures that are exposed to various damages during their service life. Offshore platforms are exposed to various damages during their useful life. This can hamper the operation of the structure and cause more damag MoreTruss structures are one of the most common offshore structures that are exposed to various damages during their service life. Offshore platforms are exposed to various damages during their useful life. This can hamper the operation of the structure and cause more damage in the future if it grows and the damage increases. The location and severity of damage to structures is usually unknown, therefore, many efforts have been made to achieve an accurate, safe and low-cost way to identify damage to marine structures. Damage detection methods based on dynamic response are one of the non-destructive and practical methods. One of the most important subfields of damage identification based on the dynamic response of the structure is the modal strain energy method. In this paper, applying the modal strain energy method, the location of the damage in an offshore wind turbine tripod platform has been identified. The results presented that the Improved modal strain energy method has a sutible ability to identify the location of single damages with appropriate accuracy, both low intensity and high intensity. Also, in the event that more than one member of the structure is damaged, the written algorithm is able to distinguish the location of the damges, but in addition to the damaged members, some other members may also exhibit a damage index greater than one. Manuscript profile -
Open Access Article
6 - Seismic Performance of RC Frames Equipped with Zipper Braces Subjected to the Near-field and Far-field Earthquakes
Seyyed Ramin Abtahi Babak BehforouzIn recent years, near-fault earthquakes have received more attention due to their variable frequency nature, pulsing motion, and causing incremental damage. On the other hand, due to the abundance of concrete structures in Iran, more than any other structures, they are MoreIn recent years, near-fault earthquakes have received more attention due to their variable frequency nature, pulsing motion, and causing incremental damage. On the other hand, due to the abundance of concrete structures in Iran, more than any other structures, they are at risk of damages caused by near-fault earthquakes. This issue clearly indicates the necessity of using new lateral bracing systems in RC structures. One of the lateral bracing systems is the combination of Chevron braces with zipper elements. Owing to this issue, the main purpose of this study is to investigate the seismic performance of RC frames equipped with zipper braced elements under near-fault earthquakes. Therefore, seven far-fault and seven near-fault earthquake records and three RC frames of 3, 6, and 9 floors with and without considering zipper elements were selected. Then, RC frames were designed using linear static analysis, after which all frames were analyzed by dynamic nonlinear time history analysis. After performing the analysis, the results such as total displacement, relative displacement, story shear, and plastic hinge formation were compared. The results of this study present that the zip-shaped elements have significantly succeeded in transferring asymmetric loads of the lower story braces to the upper stories and have prevented the creation of a soft story in the first height level of the structure. Finally, the comparison of the results ehibits the significant effect of the distance from the fault on the overall and relative deformations of the structures with increasing the height of the stories Manuscript profile -
Open Access Article
7 - A review of studies on the use of dampers to improve the seismic performance of structures
Ali SattariThe growth of population and technology along with the costs of maintenance and repair of structures after the occurrence of natural disasters such as storms, floods and earthquakes have caused people to look for safer shelter than in the past. Dampers are used to impro MoreThe growth of population and technology along with the costs of maintenance and repair of structures after the occurrence of natural disasters such as storms, floods and earthquakes have caused people to look for safer shelter than in the past. Dampers are used to improve the cyclic behavior of structures against wind and earthquake loads. In this research, the experimental and numerical research results published in open access journals that considered the effect of the type and form of the damper on the performance of the structures, including the reduction of displacement and the reduction of foundation shear, are given. By applying cyclic load to the structure, usually the dampers have reduced the base shear and reduced the displacement of the structure. In the laboratory samples where only the damper itself has been tested, more attention has been paid to the performance of the damper. As a result of applying the earthquake record to the structure, the dampers have caused a decrease in a number of records and an increase in the base shear and displacement of the structure in some records, and at the same time, they have not shown a uniform performance for the base shear and displacement. Manuscript profile
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