بررسی آزمایشگاهی اتصالات خارجی تیربه ستون بتن مسلح با میلگردهای فولادی و آلیاژهای حافظه دار شکلی تحت تاثیربارهای چرخه ای

نوع مقاله : علمی - پژوهشی

نویسندگان

1 دانشجوی دکتری مهندسی عمران ، گروه مهندسی عمران ، دانشکده مهندسی، دانشگاه فردوسی مشهد، مشهد، ایران

2 استاد، دانشکده مهندسی، دانشگاه فردوسی مشهد، مشهد، ایران

3 دانشیار ، دانشکده مهندسی، دانشگاه فردوسی مشهد، مشهد، ایران

چکیده

در این پژوهش آزمایشگاهی، رفتار اتصال خارجی تیر به ستون بتنی تحت تاثیر بارگذاری چرخه ای با میلگردهای آلیاژی حافظه دار شکلی (SMA) مورد بررسی قرار می گیرد .در این پژوهش 8 نمونه بتنی ساخته و آزمایش شد. در 4 نمونه از میلگردهای آلیاژی حافظه دار شکلی و در 4 نمونه دیگر از میلگردهای فولادی، برای اتصال تیر به ستون استفاده شده است. میزان محصور شدگی میلگردهای طولی تیر در محل اتصال نمونه‌ها ، متفاوت در نظر گرفته شده است. همچنین از دو نوع بتن، با مقاومت های 30 و 45 مگا پاسکال استفاده شده است. نمونه‌ها تحت بارگذاری چرخه ای آزمایش شدند. نتایج پژوهش نشان می دهد که میلگردهای آلیاژی حافظه دار شکلی، توانایی بالایی در بازگشت به شکل اولیه خود، بعد از تحمل تغییر مکان های بزرگ را دارند. در این مصالح مقدار جذب انرژی مناسب بوده و کاهش تغییر شکل پسماند در اتصال قابل ملاحظه می باشد. با توجه به رفتار فوق الاستیک میلگردهای آلیاژی حافظه دار شکلی، در بتن معمولی و مقاومت بالا ترک‌ها در هسته اتصال قابل ملاحظه نبوده و بارگذاری چرخه ای، موجب بسته شدن ترک‌ها در هسته اتصال گردید. با افزایش بارگذاری چرخه ای، شکست خارج از هسته اتصال به صورت خمشی و در تیر ایجاد گردید. افزایش محصور شدگی تیر باعث دور شدن محل شکست در تیر از هسته اتصال گردید. در اتصال تیر به ستون با میلگردهای فولادی، شکست برشی در هسته اتصال ایجاد شد ولی با افزایش مقاومت بتن و محصور شدگی، شکست در خارج از هسته اتصال به صورت خمشی در تیر صورت گرفت. طول مفصل پلاستیک در تیر اتصال برای نمونه‌های با میلگردهای آلیاژی حافظه دار شکلی و میلگردهای فولادی، توسط روابط تجربی و نتایج آزمایشگاهی محاسبه گردید و مشخص شد که استفاده از معادله پاول و پریستلی برای اتصالات بتنی با هر دو نوع میلگرد مناسب است.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Experimental investigation on exterior RC beam-column connections subjected to cyclic loading using steel and shape memory alloy (SMA) reinforcing bars

نویسندگان [English]

  • Hossein Rezaee Azariani 1
  • mohammad Reza Esfahani 2
  • Hashem Shariatmadar 3
1 Director of the contract office of Khorasan Razavi Regional Water Company (retired) - Currently coached by Sobhan University (Neishabur)
2 Ferdowsi University of Mashhad
3 Ferdowsi University Of Mashhad (FUM)
چکیده [English]

In the present Experimental research, the behavior of exterior RC beam-column connections subjected to cyclic loading is studied using steel and shape memory alloy (SMA) reinforcing bars. In this research, 8 specimens of exterior RC beam-column connections were tested in which four specimens included SMA reinforcing bars and the remaining four specimens included steel bars. The confinement of beam longitudinal bars was different in the connections. Also, two types of concretes were used with the strengths 30 and 45 MPa, respectively.The specimens were tested under cyclic loading. The results of the research show that the specimens with SMA reinforcing bars can return to their initial shape after tolerating large displacements. In these specimens, the energy dissipation is satisfactory and the decrease in the residual deformation is significant. According to the superelastic behavior of the SMA reinforcing bars, the width of cracks is not significant in the connection core and cyclic loading reduced the cracks in the connection core. As the cyclic loading increased, bending failure occurred in the beam outside of the connection core. As the concrete strength and confinement value increased, bending failure still occurred in the beam outside of the connection core. In the beam-column connection with steel bars, shear failure occurred in the connection core. However, as the concrete strength and confinement increased, bending failure occurred in the beam outside of the connection core. Plastic hinge length in the connecting beams were calculated in the specimens with SMA and steel bars by empirical equations and compared with the test results. It was shown that Paulay and Priestley equations were suitable to be used for concrete connections with different bars.

کلیدواژه‌ها [English]

  • Shape Memory Alloy (SMA)
  • reinforced concrete
  • Beam-Column Connection
  • Superelastic Effect
  • cyclic loading
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