ارزیابی احتمالاتی تاثیر پارامترهای خوردگی از نوع یکنواخت بر پیوستگی بین بتن و میلگرد

نوع مقاله : پژوهشی اصیل (کامل)

نویسنده
سید عباس حسینی
دانشکده صنعت و معدن چرام، دانشگاه یاسوج، ایران، چرام
چکیده
خوردگی میلگردها در سازه‌های بتن آرمه دارای اثرات مخربی است که مجموع این اثرات موجب تقلیل مقاومت و کاهش دوام این نوع سازه‌ها می‌شود. یکی از مهمترین اثرات خوردگی میلگرد، کاهش پیوستگی بین بتن و میلگرد است که در شرایط بحرانی موجب کاهش شدید مقاومت بتن و همچنین تغییر مود شکست سازه بتن مسلح می‌شود. به دلیل غیرهمگن بودن و همچنین متفاوت بودن خواص بتن‌های مختلف، مدل‌های آزمایشگاهی و تحلیلی ارائه شده برای تخمین میزان چسبندگی بتن و میلگرد برای مقادیر مختلف خوردگی دارای تفاوت‌های زیادی می‌باشند. در این مقاله با گردآوری تعداد زیادی از نتایج آزمایشگاهی موجود، چند مدل جدید با در نظر گرفتن عدم قطعیت پارامترهای موثر ارائه شده است. برای بدست آوردن این مدل‌ها نتایج آزمایشگات بر اساس قطر میلگرد دسته بندی شده اند و برای هر قطر میلگرد یک رابطه ارائه شده است. با توجه به اینکه مدل‌های ارائه شده بر مبنای درصد کاهش سطح میلگرد در طی فرآیند خوردگی می‌باشند، در این پژوهش اثر عدم قطعیت در شدت جریان خوردگی و قطر میلگرد به صورت کمی مورد بررسی قرار گرفته است. بر اساس نتایج حاصله، کاهش پیوستگی در طی دوره گسترش خوردگی به صورت تابع نمایی است و اثر عدم قطعیت چگالی جریان خوردگی بیشتر از عدم قطعیت قطر میلگرد است. اثر عدم قطعیت‌ها در ضریب تغییرات نتایج بیشتر از اثر آن بر مقدار میانگین نتایج می‌باشد. مقدار کاهش برای میلگردهای به قطر کوچکتر، کمتر از میلگردهای بزرگتر بدست آمده است به طوریکه برای میلگردهای به قطر 10 و 16 میلیمتر در خوردگی 15 درصد، نسبت پیوستگی به پیوستگی اولیه به ترتیب برابر با 46/0 و 28/0 بوده است.

کلیدواژه‌ها

موضوعات

عنوان مقاله English

Probabilistic evaluation of the effect of uniform corrosion parameters on the bond strength between concrete and reinforcement

نویسنده English

seyed abbas hosseini
faculty of technology and mining, Yasouj University, Iran, Choram
چکیده English

Reinforcement corrosion in concrete structures is considered as one of the main important issues that degrade the durability of RC structures. One of the most important effects of reinforcement corrosion is to reduce the bond between concrete and rebar. Bond strength enables the force transfer from reinforcing steel bar into concrete and guarantees the composite manner of reinforced concrete structures. Many empirical models have been developed to estimate bond strength during the corrosion propagation period. The experimental results are different depending on the test conditions and how to prepare the samples. Models presented by different researchers, even for the same basic assumptions, have fundamental differences in the predicted bond strength, which causes uncertainty in the choice of model and results. In this paper by regression of existing empirical results, some different models are presented for each bar diameter. The reinforcement diameter and corrosion current density are two basic variables in bond degradation models that have been considered for investigation of uncertainty in proposed models. Based on the results, the bond reduction during the corrosion propagation is exponential and the effect of the uncertainty of the corrosion current density is greater than the bar diameter. The effect of uncertainties on the coefficient of variation of the results is more than the effect on the mean. The bond reduction for the smaller diameter bars was lower than the larger bars such that for 10 and 16 mm diameters at 15% corrosion, the bond to primary bond ratio was 0.46 and 0.28, respectively.

کلیدواژه‌ها English

reinforcement corrosion
bond strength
probabilistic model
chloride ingress
concrete durability
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مهندسی عمران مدرس
دوره 20، شماره 5
آذر و دی 1399
صفحه 63-75