مهندسی مکانیک مدرس

مهندسی مکانیک مدرس

مطالعه های آزمایشگاهی و عددی گسترش ترک در بتن خودتراکم سبک

نویسندگان
1 دانشکده مهندسی عمران، دانشگاه تربیت دبیر شهید رجایی، تهران، ایران
2 گروه سازه، دانشکده عمران، دانشگاه تربیت دبیر رجایی، لویزان، تهران، ایران
چکیده
به منظور تعیین پارامترهای شکست بتن خودتراکم سبک دو روش مختلف اثر اندازه و کار شکست مورد استفاده قرار گرفت. برای لحاظ نمودن رفتار بتن در مقاومت‌های متفاوت، دو طرح اختلاط با نسبت‌های آب به سیمان 0.42 و0.47 در نظر گرفته شد. در ابتدا خصوصیات روانی بتن مورد بررسی قرار گرفت و بعد از اطمینان از خودتراکم بودن آن‌ها خصوصیات مکانیکی بتن سخت شده تعیین گردید. سپس با بهر‌گیری از دو روش فوق و با انجام آزمایش خمش سه محوری بر روی 30 تیر با ابعاد مختلف، پارامترهای شکست بتن و بازشدگی نوک ترک محاسبه شدند. نتایج نشان می‌دهند که با افزایش نسبت آب به سیمان از 0.42 به 0.47، انرژی‌های شکست اولیه، کل و چغرمگی شکست بتن خودتراکم سبک به ترتیب 39.4%، 33.4% و 25.3% کاهش می‌یابند. به این ترتیب ضمن مشخص شدن تاثیر مثبت کاهش نسبت آب به سیمان بر پارامترهای شکست این نوع بتن، دلایل تغییر رفتار بتن هم بررسی شد. همچنین چند رابطه تجربی ارائه گردید که با استفاده از آن‌ها می‌توان تنها با محاسبه مقاومت فشاری بتن انرژی شکست اولیه، انرژی کل، نسبت انرژی‌ها به یکدیگر و چغرمگی شکست بتن را تعیین نمود. سپس با بهره‌گیری از پارامترهای شکست، خصوصیات مکانیکی بتن و به کمک روش المان محدود توسعه یافته به مدل‌سازی معکوس پرداخته شد. نتایج بیانگر دقت بالای روش المان محدود توسعه یافته در حل عددی مسائل شکست و نیز کارآئی پارامترهای محاسبه شده برای تعیین رفتار بتن‌های خودتراکم سبک در هنگام گسترش ترک می‌باشد.
کلیدواژه‌ها

موضوعات


عنوان مقاله English

Experimental and numerical studies of crack propagation in self-compacting lightweight concrete

نویسندگان English

Hasan Salehi 1
Moosa Mazloom 2
1 Department of Civil Engineering, Shahid Rajaee Teacher Training University, Lavizan, Tehran, Iran
2 Department of Civil Engineering, Shahid Rajaee Teacher Training University, Lavizan, Tehran, Iran
چکیده English

For determination of the fracture parameters of self-compacting lightweight concrete (SCLC) size effect and work of fracture methods were used. For considering the behavior of concrete in different strengths, two mixes with water to cement (W/C) ratios of 0.42 and 0.47 were utilized. At first, the workability of the concrete was investigated and, after ensuring their self-compacting properties, the mechanical properties of the hardened concrete were determined. Then, by using the above-mentioned methods and conducting three-point bending tests on 30 beams, concrete fracture parameters, and crack-tip opening displacement were achieved. The results showed that with increasing W/C ratio from 0.42 to 0.47, the initial and total fracture energies, and fracture toughness decreased by 39.4%, 33.4% and 25.3%, respectively. The effect of the W/C ratio on the fracture parameters of this type of concrete was discussed. Furthermore, several empirical relations have been proposed that by the use of them and only by the determination of the compressive strength, the initial fracture energy, total fracture energy, the ratio of energies to each other, and fracture toughness can be determined. Then, by using the fracture parameters, the mechanical properties of the concrete and the extended finite-element method, the crack propagation was modeled. The results showed that this method has high accuracy in the numerical solution of the fracture problems as well as the efficiency of the obtained parameters for determining the behavior of self-compacting lightweight concrete.

کلیدواژه‌ها English

Self-compacting lightweight concrete
Fracture toughness
Extended finite element method
Fracture parameters
Work of fracture method
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