اثر مقاومت بتن، آرایش و نسبت میلگرد بر رفتار خمشی و ترک‌خوردگی تیرهای بتن‌آرمه مسلح شده با میلگردهای GFRP

نوع مقاله : علمی - پژوهشی

نویسندگان

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

2 دانشگاه فردوسی مشهد

چکیده

میلگردهای پلیمری مسلح الیافی (FRP) یک جایگزین مطمئن برای میلگردهای فولادی جهت مسلح کردن اعضای بتنی در محیط مرطوب است. دوام این میلگردها در برابر خوردگی، به خصوص در شرایط سخت آب و هوایی بسیار زیاد است. به دلیل مدول الاستیسیته کم این میلگردها در مقایسه با میلگردهای فولادی، خیز و عرض ترک‎ها در تیرهای مسلح شده با این میلگردها بیشتر می‎باشند. بنابراین، طراحی اعضای بتنی مسلح شده با این میلگردها در حالت بهره‌برداری کنترل کننده است. در این پژوهش، رفتار خمشی و ترک‌خوردگی تیرهای بتنی مسلح شده با میلگردهای GFRP مورد بررسی قرار می‌گیرد. به این منظور، ۱۲ نمونه تیر آزمایشگاهی به ابعاد مقطع ۲۵۰×۲۵۰ میلی‌متر و طول ۲۲۰۰ میلی‌متر ساخته شدند و به صورت دو سر ساده و تحت خمش چهار نقطه‌ای مورد آزمایش قرار گرفتند. ۸ نمونه از تیرها با نسبت آرماتور کم ساخته شدند که ۴ نمونه از آنها از بتن با مقاومت بالا و ۴ نمونه‌ی دیگر از بتن با مقاومت معمولی ساخته شدند. ۴ نمونه‌ی دیگر از تیرها با نسبت آرماتور زیاد و ساخته شده از بتن با مقاومت معمولی می‌باشند. پارامترهای مورد بررسی در این تحقیق، شامل مقاومت بتن، آرایش و نسبت میلگردهای کششی می‌باشند. نتایج پژوهش انجام شده نشان داد که تغییر در مقاومت بتن و هم‌چنین تغییر در آرایش و نسبت میلگردهای کششی، باعث تغییر در رفتار خمشی تیرها می‌شود و بر ترک‌خوردگی نیز مؤثرند. به علاوه، نتایج آزمایشگاهی این پژوهش با آیین‌نامه‌ طراحی ACI440.1R مقایسه شده است.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Effect of Concrete Strength, Arrangement/Ratio of Reinforcement on Flexural Behavior and Cracking of Concrete Beams Reinforced with GFRP Bars

نویسندگان [English]

  • Amir Mohammad Mohtaj Khorasani 1
  • mohammad Reza Esfahani 2
1 Civil Engineering Department, Faculty of Engineering. Ferdowsi University of Mashhad, Mashhad, Iran
2 Ferdowsi University of Mashhad
چکیده [English]

Fiber reinforced polymers (FRP) are the safe alternatives to steel bars in reinforced concrete members in a humid environment. They have a very high durability against corrosion, especially in the extreme weather conditions. As a result of the low modulus of elasticity of these bars compared to the steel bars, the deflection and crack width are high in the beams reinforced with these bars. In this paper, the flexural behavior and cracking of concrete beams reinforced with GFRP bars are investigated. Twelve reinforced concrete beams with the cross-section of 250 × 250 mm and length of 2200 mm were manufactured and tested in a four-point bending setup. Eight beams were made with low reinforcement ratio, 4 of which were made of high-strength concrete and 4 were made of normal-strength concrete. In addition, 4 other beams were made with high reinforcement ratio made of normal-strength concrete. The parameters studied in this research are concrete strength, tensile bars arrangement and reinforcement ratio. The results show that the change in the strength of concrete as well as the change in the arrangement of tensile bars and reinforcement ratio lead to a change in the flexural behavior of the beams and also affect the cracking. Moreover, the experimental results are compared with the values predicted by ACI440.1R code.

کلیدواژه‌ها [English]

  • RC Beams
  • Flexural Behavior
  • Cracking
  • GFRP Reinforcing Bars
  • Concrete Strength
  • Bars Arrangement
  • Reinforcement Ratio
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