برآورد ظرفیت نهایی اتصالات RBS تحت بار یکنواخت و سیکلی با استفاده از مکانیزم شکست شکل پذیر

نوع مقاله: یادداشت فنی

نویسندگان

1 دانشجوی دکتری دانشگاه سمنان

2 دانشگاه سمنان

چکیده

جهت تعیین سطح عملکرد واقعی سازه ها تحت زلزله ؛لازمست ظرفیت نهایی اتصالات تحت بار سیکلی مشخص گردد. از طرف دیگر؛ در سالهای اخیر انهدام موضعی اعضا و ایجاد خرابی پیش رونده در سازه ها در اثر انفجار و یا آتش سوزی؛ تعیین ظرفیت نهایی اتصالات تحت بار یکنواخت را اجتناب ناپذیر نموده است. در این پژوهش ظرفیت نهایی اتصالات دارای تیر با مقطع کاهش یافته RBS تحت بارگزاری یکنواخت با استفاده از سناریوی حذف ستون و با استفاده از مدل تنش مشخص-کرنش بحرانی مشخص گردید. سپس ظرفیت نهایی اتصالات مورد بررسی تحت بارگزاری سیکلی با استفاده از مدل رشد و بهم پیوستگی حفرهها تحت بار سیکلی بدست آمد تا در مواقعی که امکان انجام تست های آزمایشگاهی نمیباشد؛ بتوان با استفاده از این مدلها ظرفیت اتصال RBS را تعیین نمود. نتایج نشان میدهد ظرفیت چرخش اتصالات RBS تحت بار سیکلی کمتر از اعداد ذکر شده در نشریه FEMA350 می باشد ولی ظرفیت چرخش این نوع اتصالات تحت بار یکنواخت تقریبا دو برابر ظرفیت چرخش آنها تحت بار سیکلی میباشد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Estimated Ultimate Capacity of RBS Connections Under Monotonic and Cyclic Load Using Ductile Fracture Mechanism

نویسندگان [English]

  • Mohsen Ghaderi 1
  • mohsen gerami 2
  • reza vahdani 2
1 Semnan University
2 semnan univercity
چکیده [English]

The basis of the modern design of earthquake resistant structures is based on the structural ductility for absorption of earthquake energy and stability in large-scale displacement. Although metal materials are highly ductile, the Northridge earthquake showed that moment connections have a certain rotational capacity under cyclic load, and severe earthquakes can lead to failure in the area with low ductility. Therefore, in order to determine the level of actual performance of structures under earthquake, such as the life safety or Collapse Prevention, it is necessary to carry out more serious studies to determine the final cyclic capacity of connections. On the other hand, after the collapse of the Alfred P. Murrah Federal building, a truck explosion in 1995, as well as the collapse of the World Trade Towers caused by the 2001 airplane collapse;Determination of final capacity or failure of fittings under uniform load; to investigate the structural behavior before the destruction or complete destruction began. Since most of the tests carried out on the connections have not been completed due to the limitations of the laboratory facilities and have not been performed until the failure phase of the connection; hence, it does not determine the final capacity of the connection. Mathematical studies are also in the early stages due to the lack of reliable failure mechanism to determine the time and how to start and spread the failure under monotonic and cyclic loading. In this research,it has been attempted to be evaluated the final capacity of the RBS connections under the monotonic and cyclic load . Also, the place of the start of defect in this type of connection is evaluated. In this regard, the final capacity of the reduced-sectional beam (RBS) connections under uniform loading was determined using a column-removing scenario with the SMCS model and the theory of growth and expansion of void under uniform load. Then, the final capacity of the reduced-beam section (RBS) connections under cyclic loading (SAC) was obtained by using the Cyclic Void Growth Model (CVGM) and compared with the proposed final capacity of FEMA350 for RBS connection. The results of this study show that the cyclic rotational capacity of the RBS connections provided in FEMA350 is far more than actual. Also, the results show that the rotational capacity of the RBS connection under monotonic load is almost twice the amount given in FEMA350.

کلیدواژه‌ها [English]

  • ultimate capacity
  • monotonic load
  • cyclic load
  • reduced beam section (RBS)
  • void growth model