ارزیابی کاربرد روش "پیچش" برای تعیین مقاومت های فشاری و خمشی در جای بتن الیافی

نوع مقاله : علمی - پژوهشی

نویسندگان

1 استاد، دانشکده فنی و مهندسی، دانشگاه بین المللی امام خمینی (ره)، قزوین، ایران

2 گروه عمران، دانشکده فنی و مهندسی، دانشگاه امام خمینی (ره)، قزوین، ایران

چکیده

نظر به اینکه روش‌های آزمایشگاهی تعیین مقاومت بتن، عمدتاً کیفیت مصالح مورد استفاده در تهیه بتن را کنترل می‌نمایند و ارزیابی مناسبی از روند کسب مقاومت بتن در سازه ارائه نمی‌نمایند، انجام آزمون‌هایی جهت ارزیابی مقاومت بتن سازه از اهمیت خاصی برخوردار است. از جمله آزمون‌های با خرابی جزئی، روش "پیچش" می‌باشد که دارای کاربری وسیع در تعیین مقاومت انواع بتن هم در آزمایشگاه و هم در محل سازه می‌باشد. در این مقاله، تاثیر نوع الیاف (فولادی، شیشه‌ای و پلی‌پروپیلن) بر نتایج به دست آمده از روش "پیچش" برای تعیین مقاومت درجای بتن با به کارگیری 234 نمونه، مطالعه و نتایج حاصله ارائه گردیده است. نتایج به دست آمده نشان می‌دهد که یک همبستگی قوی خطی میان مقاومت فشاری و مدول گسیختگی با نتایج حاصل از انجام آزمون "پیچش" برقرار می‌باشد. همچنین به منظور بررسی الگوی تنش‌های ایجاد شده در بتن، چسب و استوانه آزمون "پیچش" و الگوی ایجاد و گسترش ترک‌ها در نمونه بتنی به هنگام انجام آزمون، مدل‌سازی و تحلیل غیر خطی با استفاده از نرم افزار اجزا محدود Abaqus/CAE ارائه گردیده است. انجام آنالیز اجزا محدود با لحاظ توابع شکل غیر خطی برای المان‌ها در کشش و فشار بر روی نمونه بتنی با مقاومت 40 مگاپاسکال نشان می‌دهد که با رعایت فاصله حداقل به اندازه 20 میلی‌متر تاثیری بر نتایج آزمون "پیچش" و پراکندگی آن‌ها ندارد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Assessment of the application "twist-off" method for determining the in situ compressive and flexural strengths in the fiber concrete

نویسندگان [English]

  • Mahmood Naderi 1
  • Alireza Esmaeli 2
  • Ali Saberi Varzaneh 2
1 Professor, Department of Civil Engineering, Engineering Faculty, International Imam Khomeini University, Qazvin, Iran
2 Department of Civil Engineering, Engineering Faculty, International Imam Khomeini University, Qazvin, Iran
چکیده [English]

Since the batching, transportation, pouring, compaction and curing of the specimens used in laboratory testing of concrete, either from these employed in real structures, the in-situ methods are needed for assessing the quality of existing concrete in structures. Among the tests with partial failure, the "twist-off" method is used for determining the strength of concrete both in the laboratory and in-situ. In this paper the use of “twist-off” method for determining the strength of three types of fibre concrete is presented. In total 234 concrete samples were prepared, using three types of fibre (steel, glass and polypropylene) and their strength were measured using both “twist-off” and “compression” testing. The results show that a strong linear correlation exists between the compressive strength and the failure modulus with the results of the "twist-off" test. Also, to study the pattern of stresses in concrete, glue and cylinder of the "twist-off" test and the pattern of the formation and expansion of the cracks in concrete samples during the test, nonlinear modeling and finite elements were carried out using Abaqus/CAE. The finite element analysis with consideration of the nonlinear shape functions for the elements in tension and pressure on concrete specimens with a strength of 40 MPa shows that, with the distance of at least 20 mm, the results of the "twist-off" test and dispersion are not affected.

کلیدواژه‌ها [English]

  • Concrete
  • Twist-off
  • Fibre
  • Failure Modulus
  • Nonlinear
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