بررسی آزمایشگاهی مقاوم‌سازی خمشی تیرهای سراسری بتن‌آرمه با لمینیت پیش‌ساخته کامپوزیت الیافی توانمند

نوع مقاله : علمی - پژوهشی

نویسندگان

1 دانشجوی دکتری، دانشکده عمران، دانشگاه سمنان، سمنان، ایران

2 استاد، دانشکده عمران، دانشگاه سمنان، سمنان، ایران

3 دانشیار، دانشکده عمران، دانشگاه سمنان، سمنان، ایران

10.22065/jsce.2019.194981.1909

چکیده

هدف از این مطالعه آزمایشگاهی، بررسی تاثیر استفاده از لمینیت پیش‌ساخته کامپوزیت الیافی توانمند در مقاوم‌سازی تیرهای سراسری، بر ظرفیت باربری، شکل‌پذیری و ظرفیت استهلاک انرژی این تیرها است. همچنین تاثیر کاشت میلگرد در لمینیت پیش‌ساخته بر بهبود رفتار خمشی این تیرها بررسی شده است. کامپوزیت الیافی توانمند، یک کامپوزیت پایه‌سیمانی با مشخصات مکانیکی قابل توجه و دوام بالا است. به منظور بررسی تاثیر لمینیت‌های کامپوزیتی الیافی بر رفتار خمشی تیرها، هشت نمونه تیر بتن‌آرمه دو دهانه در دو گروه چهارتایی با مقادیر مختلف آرماتور فشاری ساخته و در هر گروه یک نمونه به عنوان نمونه مرجع، بدون مقاوم‌سازی بارگذاری شد. یکی از نمونه‌های هر گروه با لمینیت کامپوزیتی در ناحیه کششی وسط دهانه‌ها و تکیه‌گاه میانی و دو نمونه دیگر با لمینیت حاوی آرماتور طولی در همان نواحی مقاوم‌سازی شدند. آزمایشات نشان داد که ظرفیت باربری نمونه‌های مقاوم‌سازی شده بین 33 تا 59 درصد، ظرفیت استهلاک انرژی آنها بین 16 تا 35 درصد و سختی اولیه آنها تا دو برابر نمونه‌های مرجع افزایش یافت. شکل‌پذیری نمونه‌های مقاوم‌سازی شده با لمینیت فاقد آرماتور، 23 درصد نسبت به نمونه‌های مرجع کاهش یافت. اما وجود آرماتور در لمینیت باعث افزایش 5 تا 10 درصدی شکل‌پذیری نسبت به نمونه های مقاوم‌سازی شده با لمینیت فاقد آرماتورشد. نتایج این بررسی، موئد مفید بودن استفاده از لمینیت‌های پیش‌ساخته کامپوزیتی در بهبود رفتار خمشی تیرهای سراسری بتن‌آرمه است. همچنین کاشت میلگرد در لمینیت، علاوه بر افزایش ظرفیت باربری، مانع از کاهش قابل توجه شکل‌پذیری نمونه مقاوم سازی شده می‌شود.

کلیدواژه‌ها


عنوان مقاله [English]

Flexural Strengthening of Continuous RC Beams Using HPFRCC Precast Laminates

نویسندگان [English]

  • Alireza Bitaraf 1
  • Ali Kheyroddin 2
  • Mohammad Kazem Sharbatdar 3
1 Ph.D. Candidate, Faculty of Civil Engineering, Semnan University, Semnan, Iran
2 Professor, Faculty of Civil Engineering, Semnan University, Semnan, Iran
3 Associate Professor, Civil Engineering Faculty, Semnan University, Semnan, Iran
چکیده [English]

In this study, the use of precast laminates, made of high-performance fiber-reinforced cementitious composite (HPFRCC), was investigated for strengthening of continuous reinforced concrete (RC) beams. HPFRCCs are characterized by their high tensile strength and remarkable durability properties. To find the effect of strengthening, eight continuous (two-bay) RC beams were tested under monotonic load in the middle of spans; two of which were the control specimens and six of which were strengthened specimens. The HPFRCC laminates were prefabricated with 25 mm thickness and bonded to the tensile surface of beams using epoxy and mechanical anchorage. The longitudinal bars were added to laminates in four specimens to survey their effect on strengthened beams. Comparison of results declared that the load carrying capacity was increased up to 59 % in strengthened beams.  Ductility index of the strengthened beams was acceptable, and also up to 35 % growth in energy-absorption capacity was observed. Applying laminates to the tensile surface delayed crack propagation and decreased the midspan deflection. Also, stiffness of specimens in the cracked concrete stage was increased up to 78 % that led to decrease the service deflection. It is concluded that the use of HPFRCC laminates, especially in case of applying longitudinal bars, is an efficient method to enhance the flexural capacity of continuous RC beams.

کلیدواژه‌ها [English]

  • HPFRCC
  • RC continuous Beam
  • strengthening
  • Load-bearing capacity
  • Ductility
  • Energy-absorption
  • Precast laminate
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