بررسی آزمایشگاهی پارامترهای شکست تیر بتنی ساخته شده از ماده مرکب سیمانی مهندسی شده

نوع مقاله : مقاله پژوهشی

نویسندگان

دانشکده مهندسی، دانشگاه فردوسی مشهد، مشهد، ایران

چکیده

وجود ترک در سازه­های بتنی سبب می­ شود که در بسیاری از موارد معیار­های متداول قادر به پیش­بینی صحیح شکست آن‌ها نباشند. با بهره ­گیری از علم مکانیک شکست و معیارهای موجود آن می­توان رفتار شکست این­گونه سازه­ ها را به درستی پیش­ بینی کرد. در این پژوهش آزمایشگاهی با استفاده از روش­ های مکانیک شکست، پارامتر­های شکست تیر خمشی ساخته شده از ماده مرکب سیمانی مهندسی شده (ECC) مورد بررسی قرار می­ گیرد. 6 نمونه تیر آزمایشگاهی شکاف‌دار با ابعاد 100×100×350 میلی­متر مکعب بر اساس روش کار شکست (WFM) و 18 نمونه تیر آزمایشگاهی شکاف‌دار با ابعاد 70×70×190، 70×140×380 و 70×280×760 میلی­متر مکعب بر اساس روش اثر اندازه بازانت (SEM) ساخته و آزمایش شدند. مواد مورد استفاده برای تهیه ECC شامل الیاف پلی­پروپیلن، سیمان، غبار کوره آهن، میکروسیلیس و پودر سنگ بودند. از دو نسبت الیاف (1 و 2 درصد) در مخلوط­ های مختلف استفاده شد. مشاهده شد که با افزایش الیاف از 1 درصد به 2 درصد مقدار مقاومت خمشی، انرژی شکست در روش  WFM(GF)، انرژی شکست در روش SEM (Gf) و چقرمگی شکست (KIC) نمونه­ ها افزایش می‌یابند. از طرف دیگر، مقاومت فشاری، طول مشخصه (Lch) و عدد تردی نمونه­ ها با افزایش الیاف کاهش می­ یابند. همچنین قانون اثر اندازه بازانت در نمونه­ های مختلف ساخته شده از ECC مورد بحث و بررسی قرار گرفت.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

An Experimental Investigation on Fracture Parameters of Concrete Beams Made of Engineered Cementitious Composites (ECC)

نویسندگان [English]

  • Seyed Mahdi Amirfakhrian
  • M. R. Esfahani
Faculty of Engineering, Ferdowsi University of Mashhad
چکیده [English]

Due to the existence of cracks in concrete structures, the conventional strength criteria may not be able to predict their failure. It has been shown that the theories of fracture mechanics can predict the behavior of these structures appropriately. In this experimental and analytical study, by using fracture mechanics theories, fracture parameters of flexural different specimens made of Engineered Cementitious Composites (ECC) are investigated. 24 flexural specimens with the notch at their mid-length were manufactured and tested. Six of these specimens with the dimensions of 350×100×100 mm were conducted under Work of Fracture Method (WFM) and other 18 specimens with the dimensions of 190×70×70 mm3, 380×140×70 mm3 and 760×280×70 mm3 were studied under Size Effect Method (SEM). The materials used for ECC included polypropylene fibers, cement, iron furnace slag, silica fume and stone powder. Two ratios of fibers (1% and 2%) were used in different mixtures of ECC. It was observed that by increasing fibers from 1% to 2%, the amount of flexural strength, fracture energy and fracture toughness (KIC) of the specimens increased. On the other hand, compressive strength, characteristic length (Lch) and brittleness number of specimens decreased. The Bažant’s size effect law was also discussed for the ECC specimens.

کلیدواژه‌ها [English]

  • Engineered Cementitious Composite (ECC)
  • Fracture Energy
  • Toughness
  • Work of Fracture Method (WFM)
  • Size Effect Method (SEM)

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نشریه مهندسی عمران امیرکبیر
دوره 54، شماره 8
آبان 1401
صفحه 2877-2894

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