عملکرد اتصال پیچی لینک به دستک در قاب های خمشی درختی تحت اثر آتش سوزی

نوع مقاله: علمی - پژوهشی

نویسندگان

1 دانشیار، دانشکده مهندسی عمران، دانشگاه صنعتی خواجه نصیرالدین طوسی

2 دانشجوی دکتری مهندسی سازه، دانشکده مهندسی عمران، دانشگاه صنعتی خواجه نصیرالدین طوسی

چکیده

یکی از سیستم‌های سازه‌ای کارآمد در ساختمان‌های فولادی، قاب‌های خمشی درختی با اتصالات پیچی می‌باشند که در سال‌های اخیر به میزان وسیعی مورد استفاده قرار گرفته‌اند. تحقیقات بسیار اندکی بر روی رفتار این سیستم در شرایط آتش‌سوزی صورت گرفته است. این مقاله به بررسی آزمایشگاهی رفتار تیر و اتصالات وصله‌ای پیچی در قاب‌های خمشی درختی تحت اثر آتش می‌پردازد. بدین ‌منظور دو قاب فولادی با اتصالات متفاوت در مقیاس واقعی تحت اثر آتش استاندارد ایزو 834 آزمایش گردید. رفتارهای سازه‌ای و حرارتی نمونه‌ها در آتش، شامل تاریخچه دماها، نمودارهای دما - خیز و زمان - خیز تیر، دما - دوران اتصال و مودهای خرابی مطالعه شده است. مشاهده گردید که اتصال تیر میانی به دستک به علت گسیختگی برشی پیچ‌های وصله بال بالایی در دمای بالاتر از C°750 دچار خرابی می‌گردد و این درحالیست که تیر خیزهای بزرگی بیش از یک بیستم دهانه را تجربه می‌نماید. همچنین استفاده از ورق‌های دوبل با پیچ‌های دوبرشه در وصله بال می‌تواند باعث بهبود تاب حرارتی و ظرفیت دورانی اتصالات وصله‌ای پیچی تیر شود.

کلیدواژه‌ها


عنوان مقاله [English]

Performance of Link-To-Stub Bolted Connection in Column-Tree Moment Resisting Frames under Fire Conditions

نویسندگان [English]

  • Mahmood Yahyai 1
  • Abbas Rezaeian 2
1 Associate Professor,Department of Civil Engineering, K.N. Toosi University of Technology
2 PhD Scholar of Structural Engineering, Department of Civil Engineering, K.N. Toosi University of Technology
چکیده [English]

Column-tree moment resisting frames, as the efficient shop-welded and field-bolted structural systems, are used in many countries. Very limited research has been carried out on such systems under fire conditions. This paper presents experimental investigations of the behavior of beam and bolted splice connections in steel column-tree moment resisting frames exposed to fire. Two full-scale steel sub-frames with different splice connections were tested under ISO 834 standard fire. The flange splice plates were configured as a single plate with single shear bolts in first specimen, and as double plates with double shear bolts in second specimen. The observation of thermal and structural fire behaviors including temperature histories, temperature-deflection of the beam, temperature-rotation of splice connections and failure modes were investigated. The temperature-deflection and temperature-rotation curves remained in the elastic range until about 600°C. Beyond 600°C, the behavior would be highly nonlinear plastic. The beam splice connection failed due to shear fracture of top bolts at temperatures beyond 750°C. Consequently, stub beam web failed at those temperatures because of block-shear. Using double plates with double shear bolts for flange splices would enhance the temperature resistance and rotational capacity of the beam splice connections. Both tests results confirmed that specimens retain the capacity to support the design load when the average beam temperature does not exceed 600°C. This temperature limit confirms the temperature criteria provided by ASTM E119 and ANSI/UL 263 for a restrained beam, and can be used to specify the minimum fire resistance criteria for beams in column-tree MRFs. The measured time-deflection curves showed that the restrained fire resistance rating for both unprotected specimens obtained about 15 minutes in both tests.

کلیدواژه‌ها [English]

  • experimental study
  • steel beam
  • Bolted connection
  • Failure modes
  • Fire
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