مطالعه آزمایشگاهی اثر کامپوزیت‌های سیمانی مهندسی حاوی نانوالیاف کربن بر اتصال بتنی تیر- ستون

نوع مقاله : علمی - پژوهشی

نویسندگان

1 عضو هیئت علمی دانشگاه رازی

2 گروه مهندسی عمران، دانشکده فنی و مهندسی، دانشگاه رازی ، کرمانشاه

چکیده

اتصالات تیر به ستون بتنی در شکل پذیری سازه، جذب انرژی و به تاخیر انداختن خرابی نقش مهمی را ایفا می‌کنند. در این پژوهش به تاثیر کامپوزیت‌های سیمانی مهندسی حاوی نانو الیاف کربن (CNF-ECC) بر روی رفتار اتصال تیر به ستون بتنی تحت بارگذاری چرخه‌ای پرداخته شده است. رفتار سخت شوندگی کرنش تحت کشش از کامپوزیت‌های سیمانی مهندسی (ECC) یک مصالح توانمند با قابلیت جذب انرژی بالا و قابلیت ترک خوردگی های زیاد قبل از شکست، ساخته است. از آنجایی که ECC یک مصالح نسبتا جدید است، عمده پژوهش های انجام گرفته، بر روی شناخت ماهیت این مصالح، ترکیبات مختلف آن، نسبت های مختلف اختلاط مصالح، روابط حاکم بر منحنی تنش-کرنش، ابداع کامپوزیت های جدید و سایر موارد مشابه متمرکز بوده است. تحقیقاتی نیز بر روی کاربردهای عملی آن در سازه ها انجام گرفته است. اما این مطالعات به اندازه تحقیقات مربوط به شناخت رفتار خود مصالح، گسترده نبوده و نیازمند انجام کارهای تحلیلی و آزمایشگاهی فراوان است. در این پژوهش 3 اتصال بتنی مورد آزمایش قرار گرفت که یکی از اتصالات به عنوان نمونه مرجع و در 2 اتصال دیگر، در طول ناحیه بحرانی اتصال تیر به ستون با ECC و CNF-ECC جایگزین گردید. پارامترهای اصلی درنظر گرفته شده شامل منحنی های هیسترزیس لنگر- تغییر مکان نسبی، ظرفیت جذب انرژی و توزیع ترک‌ها است. نمونه‌های آزمایشگاهی تحت بارگذاری چرخه ای در انتهای تیر با کنترل تغییر مکان قرار گرفتند. بارگذاری تا زمانی که کاهش بار به بیش از 30 تا 40 درصد حداکثر بار وارده می‌رسید، ادامه می‌یافت. نتایج آمایشگاهی نشان داد که با استفاده از این مصالح توانمند، شکل پذیری و جذب انرژی این اتصالات به صورت موثری بهبود یافت و ترک‌ها ایجاد شده در چشمه اتصال به صورت یک شبکه متراکم از ریز ترک‌ها با عمق و عرض بسیار کم ظاهر گردید

کلیدواژه‌ها


عنوان مقاله [English]

Experimental study of the effect of engineering cementitious composites containing carbon nanofibers on concrete-beam-column joint

نویسندگان [English]

  • Ebrahim Kalilzadeh Vahidi 1
  • mohammad rezaei 2
1 Assistant Professor, Razi University
2 Department of Civil Engineering, Faculty of Engineering, Razi University, Kermanshah
چکیده [English]

Concrete beam-column joint perform an important role in structural ductility, energy absorption and delaying breakdown. In this study, the effect of engineered cementitious composites containing carbon nanofibers (CNF-ECC) on the behavior of T-shaped concrete beam-column connections under cyclic loading is investigated. The tensile strain hardening behavior of ECCs has made a powerful material with high energy absorption and high cracking potential before failure. Since ECC is a relatively new material, much of the research has focused on understanding the nature of these materials, their different constituents, different mixing ratios, the stress-strain curve relationships, the invention of new composites. Research has also been done on its practical applications in structures. But these studies are not as extensive as research on the behavior of materials themselves, and require a great deal of analytical ad laboratory work. In this study, three concrete joints were tested, one of which was replaced as a reference specimen and the other two joints were replaced with ECC and CNF-ECC. The main parameters considered include hysteresis Moment curves - relative drift, energy absorption capacity, and crack distribution. Experimental models were subjected to cyclic loading at the end of the beam with displacement control. The loading continued until the load reduction reached more than 30-40% of the maximum load. The results show that by using these high- performance materials, the ductility and energy absorption of these joints are effectively improved. The results showed that using these powerful materials, the ductility and energy absorption of these joints were effectively improved and the cracks created in the connection spring as a dense network of micro-cracks with very shallow depth and width. respectively.

کلیدواژه‌ها [English]

  • Experimental study
  • Beam-column joint
  • Normal concrete (NC)
  • ECC
  • Carbon nano fiber (CNF)
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