بررسی زمان شروع خوردگی سازه‌های بتن ‌آرمه در فواصل مختلف از دریا

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشکده مهندسی عمران، دانشگاه علم و صنعت ایران، تهران، ایران

2 دانشکده مهندسی عمران، واحد تهران شرق، دانشگاه آزاد اسلامی، تهران، ایران

چکیده

یکی از آسیب­ هایی که در سازه ­های بتن آرمه به وجود می­ آید و باعث می­ شود که سازه مورد نظر عملکرد مورد انتظار را در هنگام وقوع زلزله محتمل نداشته باشد، خوردگی آرماتور می ­باشد. سازه­ های بتن آرمه نزدیک به ساحل، پل ­هایی که در معرض نمک یخ زدایی در فصل زمستان هستند، پایه ­های سازه­ های دریایی که تحت اثر جزر و مد هستند، از جمله مواردی است که خوردگی باعث آسیب در عملکرد مورد انتظار می ­شود. خوردگی بیشتر تحت دو عامل کلر (خوردگی حفره­ای) و کربناسیون (خوردگی یکنواخت) رخ می­ دهد. بعد از عبور این یون­ ها از پوشش فیزیکی (کاور بتنی) و پوشش شیمیایی (لایه محافظ غیرفعال دور میلگرد) به سطح میلگرد رسیده و خوردگی آغاز می­شود. در اثر خوردگی خصوصیات مکانیکی فولاد و بتن کاهش یافته و عملکرد لرزه­ای سازه را تحت تأثیر قرار می ­دهد. یکی از پارامترهای مهم در بررسی آثار خوردگی بر عملکرد لرزه ­ای در طول عمر مفید سازه، زمان شروع خوردگی می­ باشد. بر اساس قانون فیک زمان شروع خوردگی تابعی از کلرید سطحی، ضریب انتشار کلرید در بتن، پوشش بتنی روی آرماتورها و کلرید بحرانی می‌باشد. در این تحقیق خوردگی ناشی از کلر در نظر گرفته شده است. زمان شروع خوردگی در دو حالت غیراحتمالاتی و احتمالاتی مونت کارلو (با در نظر گرفتن عدم قطعیت‌ها­ در پارامترهای تأثیرگذار بر پیش‌بینی زمان شروع خوردگی) تعیین می‌شود. در پایان با مقایسه این دو حالت با یکدیگر میزان تأثیر عدم قطعیت‌ها در احتمال زمان شروع خوردگی نشان داده شده است. همچنین میزان اثر فاصله از دریا و نسبت آب به سیمان‌های متفاوت نیز در نظر گرفته شده است.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Investigation of the corrosion initiation time of reinforced concrete structures at different distances from the Sea

نویسندگان [English]

  • Amirhossein Jafary 1
  • mohsen ali shayanfar 1
  • Mohammad Ghanooni-Bagha 2
1 Department of Civil engineering, Iran University of Science and Technology, Tehran, Iran
2 Department of Civil Engineering, East Tehran Branch, Islamic Azad University, Tehran, Iran
چکیده [English]

Corrosion is one of the crucial damages that may occur to reinforced concrete structures. It also may affect the expected performance of the structure during possible earthquakes. Onshore reinforced structures, bridges exposed to deicing salts in winter and also the pillars of marine structures under tidal waves, all of which are examples of corrosion damages. Corrosion mostly occurs due to two main reasons: chloride and carbonation which cause pitting corrosion and uniform corrosion, respectively. Corrosion starts with the reaching of those two ions to the bar surface, passing by the physical and chemical passive covers. Corrosion also affects the mechanical properties of the steel and the concrete and reduces the seismic performance of the structure. One of the most important parameters in studying corrosion and its effects on the seismic performance and life cycle of the structure is the corrosion initiation time. According to Fick’s law, the initiation time is a function of surface and critical chloride, chloride diffusion coefficient and concrete cover on armatures. In the present study, the chloride-based corrosion is considered. Besides, corrosion initiation time is determined by deterministic and probabilistic Monte-Carlo methods considering the uncertainties in the effective parameters. In the end, by comparing these two methods, the effect of uncertainties in the possibility of corrosion initiation time is presented. Furthermore, parameters like the distance from the sea and the water-to-cement ratio are discussed in a parametric study.

کلیدواژه‌ها [English]

  • Concrete structures
  • Corrosion
  • Corrosion initiation
  • Monte-Carlo Simulation
  • Uncertainties
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