مطالعه عددی و آزمایشگاهی گسیختگی بتن تقویت شده با ورق CFRP تحت بارگذاری کششی و برشی

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشکدة فنی و مهندسی، دانشگاه بین المللی امام خمینی (ره)

2 دانشگاه بین‌المللی امام خمینی (ره)، قزوین، ایران

چکیده

در این مقاله مقاومت چسبندگی و نحوه گسیختگی بتن تقویت شده با ورق CFRP تحت تنش‌های کششی و برشی با استفاده از روش‌‌ المان محدود غیرخطی و روش آزمایشگاهی بررسی می‌گردد. با توجه به اینکه در بررسی رفتار مکانیکی بتن تقویت شده با ورق CFRP فرض همگن بودن بتن منجر به نتایج غیرواقعی می‌شود، لذا در مقاله حاضر از مدل میان‌مقیاس برای مدل‌سازی بتن استفاده شده است. در مدل میان‌مقیاس بتن به عنوان یک ماده غیرهمگن سه فازه مشتمل بر سه فاز سنگدانه، ملات و ناحیه انتقال (ITZ) در نظر گرفته می‌شود. در مدل عددی برای شبیه‌سازی چسب در ناحیه اتصال ورق CFRP به بتن از مدل ناحیه چسبنده (CZM) موجود در نرم‌افزار آباکوس استفاده شده و نتایج بدست آمده از روش المان محدود با نتایج آزمایشگاهی مقایسه شده است. آزمایش‌های انجام شده شامل آزمایش "کشش از سطح" و "پیچش" می‌باشد. نتایج ارائه شده نشان می‌دهد مقاومت چسبندگی کششی و برشی در مدل المان محدود به ترتیب 18% و 13% بیشتر از نتایج مربوط به آزمایش "کشش از سطح" و "پیچش" بدست آمده است. همچنین مقاومت چسبندگی کششی حاصل از مدل عددی و آزمایشگاهی به ترتیب 34% و 33% کمتر از مقاومت چسبندگی برشی بدست آمده است. مطابق نتایج بدست آمده، جداشدگی در نمونه بتنی تقویت شده با ورق CFRP از بتن بستر بوده است. نتایج حاکی از آن است که ریزترک‌‌ها و به دنبال آن گسیختگی در فاز‌های ملات و ITZ بتن به دلیل تخلخل بالا و مقاومت کمتر نسبت به فاز سنگدانه، به راحتی گسترش می‌یابد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Numerical and experimental study of failure mode of CFRP strengthened concrete under tension and shear loading

نویسندگان [English]

  • roza rahbari 1
  • Mahmood Naderi 2
1 Department of Civil Engineering, Engineering Faculty, International Imam Khomeini University, Qazvin, Iran
2 Department of civil engineering, Faculty of engineering, International Imam Khomeini university, Qazvin, Iran
چکیده [English]

Today, the use of carbon fiber reinforced polymers (CFRP) is used as an efficient method for the reinforcement of concrete structures. Concrete structures strengthened with CFRP sheets may have a failure due to debonding mechanisms. In this study, the bond strength and failure mode of CFRP strengthened concrete in tensile and shear stresses are investigated using nonlinear finite element and experimental methods. Because in the study of mechanical behavior of concrete strengthened with CFRP sheet, the assumption of homogeneity of concrete leads to unrealistic results, so in this study, a mesoscale model is used to model concrete. The mesoscopic model of concrete includes three-phase inhomogeneous material consisting of aggregate, mortar, and Interfacial Transition Zone (ITZ). Tests performed include "pull-off" and "twist-off" to determine tension and shear bond strength. The results show that the tension and shear strength of the finite element model is 18% and 13% higher than the results of the "pull-off" and "twist-off" tests, respectively, which are due to laboratory influencing factors and ignoring They are acceptable in numerical modeling of this difference. Also, the tensile strength of the numerical and experimental models is 34% and 33% lower than the shear strength, respectively. According to the obtained results, the debonding in the CFRP strengthened concrete sample was from the substrate concrete. The results show that the micro-cracks, followed by debonding in the mortar and ITZ phases of concrete, due to high porosity and lower strength than the aggregate phase, spread easily.

کلیدواژه‌ها [English]

  • CFRP strengthened concrete
  • meso-scale
  • cohesive zone
  • Pull-off
  • Twist-off
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