passive control system
در نشریات گروه عمران-
یکی از روش های جلوگیری از انتقال مستقیم نیروی زلزله از زمین به سازه، جداسازی لرزه ای است. درواقع در جداسازی لرزه ای، هدف اصلی کاهش مقدار شتاب ها و نیروهایی است که در اثر زلزله به سازه منتقل می شود. این هدف با نصب سازه بر روی لایه های جداکننده که انعطاف پذیری افقی زیادی دارند انجام می گیرد. به این ترتیب هنگام زلزله که زمین زیر سازه به شدت ارتعاش می کند، حرکات چندانی به سازه منتقل نمی شود. در این پژوهش به ارائه یک شاخص جدید جهت مقایسه عملکرد سیستم جداسازی پایه پرداخته شده است که می تواند باعث طراحی سیستم جداسازی پایه با عملکرد بهتر برای سازه گردد. با استفاده از این شاخص به نام عملکرد نسبی وزنی (WRPI)، می توان عملکرد سازه و سیستم جداسازی پایه را علاوه بر درنظرگرفتن مقدار انرژی کرنشی جذب شده در سازه و جداساز، برای مقدار شتاب ماکزیمم و جابه جایی ایجاد شده در سازه و جداساز نیز مقایسه و طراحی کرد. جهت بررسی کارایی شاخص پیشنهادی و مقایسه با شاخص های پیشین، یک قاب خمشی فولادی شش طبقه با و بدون جداساز مورد مطالعه قرار گرفت. به صورت کلی شاخص WRPI نسبت به شاخص های مورد استفاده پیشین، دارای کارایی و عملکرد بهتری به ویژه در سازه های حساس به شتاب و تغییر شکل های بین طبقه ای می باشد.
کلید واژگان: شاخص عملکرد نسبی وزن دار، جداساز لرزه ای، سیستم جداسازی پایه، سیستم کنترل غیرفعال، ارزیابی عملکرد سازهOne of the methods to prevent the direct transmission of earthquake forces from the ground to a structure is seismic isolation. The main goal of seismic isolation is to reduce the amount of acceleration and forces transferred to the structure during an earthquake. This goal is achieved by installing the structure on separating layers that possess high horizontal flexibility. In this way, when the ground beneath the structure vibrates strongly during an earthquake, minimal movement is induced in the structure. In this research, a new index has been introduced to compare the performance of base isolation systems, which can lead to the design of base isolation systems with improved performance for the structure. By utilizing the proposed index, known as the Weighted Relative Performance Index (WRPI), the performance of both the structure and the base isolation system can be evaluated. This evaluation considers the amount of strain energy absorbed in the structure and the isolator, as well as the maximum acceleration value and the displacement created in both the structure and the isolator. To evaluate the effectiveness of the proposed index and compare it to previous indices, a 6-story steel moment frame with and without base isolation system was studied. Overall, the WRPI index demonstrates better efficiency and performance than previously used indices, particularly in structures sensitive to acceleration and inter-story drifts.
Keywords: Weighted Relative Performance Index, Seismic Isolator, Base Isolation System, Passive Control System, Evaluate Structure Performance -
One of the problems of common bracing system is their buckling against compressive loads, which reduces the amount of energy loss of the structure. Buckling Restrained Brace (BRB) have solved the problem of conventional braces by eliminating the overall buckling of thebrace under pressure. Buckling Restrained Braced Frame (BRBF) is a new type of bracing system that has been widely used in recent years. Nowadays the use of buckling restrainedbraces, due to having more advantages compared to conventional steel braces, have received the attention of researchers and engineers that these advantages include: high ductility, more energy loss, no overall and local buckling, andalso having a symmetrical cyclic curve. This type of bracing is considered as one of the effective systems for dealing with lateral loads caused by the earthquake.Disadvantages in the seismic behavior of conventional braces, such as ductility and low energy loss, general and local buckling, as well as having an asymmetric cyclic curve, have provided grounds for its modification or exclusion from the seismic design process. Buckling restrainedbraces are a type of energy loss system that, in addition to providing high lateral stiffness, increase the formability and energy loss of the structure. The use of this type of braces is allowed in the regulations of some countries. But in some other countries, including Iran, it has not been mentioned. According to the seismicity of the country and the increasing use of these structures in the world, the use and localization of this type of bracing system in Iran is inevitable, and the entry of this lateral bearing system into the design regulations, especially the earthquake regulations of Iran, is mandatory. The results of the analysis show that the energy loss capacity of the buckling restrainedbrace is about 5 times the energy loss capacity of the normal brace.
Keywords: buckling restrainedbrace, hysteresis behavior, energy loss, cyclic load, resistance, passive control system
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