پديد آورندگان :
شايانفر، محسنعلي دانشگاه علم و صنعت ايران - گروه مهندسي عمران , قانوني بقا، محمد دانشگاه آزاد اسلامي واحد تهران شرق - گروه مهندسي عمران , عسگراني، سعيد دانشگاه علم و صنعت - مهندسي عمران سازه
كليدواژه :
سازه هاي بتن آرمه , خوردگي كلريدي , طراحي دوام , شبيه سازي مونت كارلو
چكيده فارسي :
شرايط مهاجم محيط هاي دريايي به علت حمله يون هاي كلريد سبب خوردگي آرماتورها مي شود. اين امر خرابي هاي بسياري را به دنبال داشته و ممكن است به خرابي پيش از دوره طراحي و عمر مفيد سازه منجر شود. رايج ترين مدل هاي تخمين عمر مفيد سازه هاي بتن مسلح تحت بارگذاري كلريد، تنها يك زمان قطعي منحصر براي آغاز خوردگي توليد مي كنند. در صورتي كه نفوذ كلرايد به داخل بتن و رخداد خوردگي پديده اي احتمالاتي و غير قطعي مي باشد. بر اساس قانون فيك زمان شروع خوردگي تابعي از كلريد سطحي، كلريد بحراني، ضخامت پوشش بتن و ضريب انتشار پذيري است. در اين مقاله، از روش احتمالاتي مونت كارلو براي تخمين عمر مفيد سازه براي پيش بيني زمان شروع خوردگي استفاده شده و تاثير تغييرات ميانگين و انحراف معيار هر يك از پارامترهاي موثر بر وقوع خوردگي، بر روي زمان شروع خوردگي و ميزان تاثير اين ضرايب بر احتمال شروع خوردگي نشان داده شده است.
چكيده لاتين :
Corrosion of Reinforcement is the most important cause of damage and failure in reinforced concrete structures. Neglecting corrosion occurrence and its progress may take the structures out of use before their due date and can lead to loss of construction and maintenancecapitals. Today, more than ever, most of impairments during serviceability of concrete structures are concerned to steel corrosion especially in marine structures and concrete bridges. According to the researches, corrosion happens in two forms: Chloride and Carbonation. Normally, high alkaline property of concrete forms a protective oxide layer on the steel surface. This is called a passive protection. The dioxide existing in the atmosphere or the chloride in the concrete environment along with the moisture and the oxygen can penetrate via the concrete pores and cracks and can reach the rebar surface; then, by reducing concrete alkalinity, they cause rebar corrosion inside the concrete by destroying the protective oxide layer on the steel. In coastal areas, Chloride ion ingress is one of the major problems that affect the durability of reinforced concrete structures such as bridge decks, concrete pavements, and other structures exposed to harsh saline environments. Therefore, durability based design of concrete structures in marine areas has gained great significance in recent decades and various mathematical models for estimating the service life of reinforced concrete have been proposed. In spite of comprehensive researches on the corrosion of reinforced concrete, there are still various controversial concepts. Effect of environmental conditions on durability of concrete structures is one of the most important issues. Hence, regional investigations are necessary for durability-based design and evaluation of the models proposed for service life prediction. The Persian Gulf is one of themost aggressive regions of the world because of elevated temperature and humidity as well as high content of chloride ions in seawater. Corrosion of reinforcement due to chloride ions attack causes enormous damages to structures in severe condition of marine environments. Since each influencing factor in the life time of the structure is subject to random variability and inherent uncertainties, a stochastic approach is utilized to predict the time for initiation of the corrosion. Based on Fick’s law, time for corrosion is a function of surface chloride, critical chloride, concrete cover thickness, and diffusion coefficient. The most common models service-life predictionof reinforced concrete structures under load chloride, only produce a limited definite time for the start of corrosion. In this paper monte carlo analysis use for service life prediction of reinforced concrete structures. In process of predict the time of corrosion initiation, it shown the influence of variation of mean for each parameters that affect the occurrence of corrosion that are concrete cover on reinforcement, chloride threshold, amount of chloride concentration on surface and chloride diffusion coefficient of concrete.
