IJE TRANSACTIONS A: Basics Vol. 26, No. 10 (October 2013) 1103-1110   

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H. Dehghani and M. J. Fadaee
( Received: February 23, 2013 – Accepted in Revised Form: May 16, 2013 )

Abstract    The structural reliability of torsional concrete beams strengthened with full and strip wrapping of carbon fiber reinforced polymer (CFRP) laminate is investigated. The first order-second moment reliability method has been applied to make a reliability assessment on the torsional capacity design by technical guideline in Iran. The code No.345 published by the Management and Planning Organization of Iran (MPO 345-2006) is the first technical code in Iran for design of concrete members strengthened with CFRP laminate. In this work, the average reliability indexes for unstrengthened, strengthened with full wrap and strengthened with strip wrap beams have been found. The results indicate that the MPO design guideline are some unconservative. A reliability strengthening ratio is introduced for assessment of the variation in average reliability index before and after strengthening with different resistance factors. A parametric study on this factor reveals that if the reliability level of the strengthened reinforced concrete beams is kept to be consistent with their similar unstrengthened beams, a value of 0.89 and 0.81 for strengthened with full wrap and strengthened with strip wrap, respectively, should be applied.


Keywords    CFRP Laminate, Reliability Indexes, Torsion, Concrete Beams, MPO Guideline


چکیده    در این مقاله قابلیت اطمینان سازه ای تیرهای بتن آرمه تقویت شده با پلیمرهای مسلح شده با الیاف کربن((CFRP به صورت دورپیچ کامل و نواری تحت اثر پیچش بررسی شده است. برای ارزیابی قابلیت اطمینان ظرفیت پیچشی، طراحی بر اساس راهنمای طراحی ایران انجام و سپس روش قابلیت اطمینان مرتبه اول- لنگر دوم بکار برده شده است. اولین آیین نامه برای طراحی اعضای بتن آرمه تقویت شده با CFRP در ایران، نشریه شماره 345 سازمان مدیریت و برنامه ریزی کشور (MPO 345-2006) می باشد. در تحقیق حاضر، میانگین شاخص قابلیت اطمینان برای تیرهای تقویت نشده و تیرهای تقویت شده با دورپیچ کامل و نواری بدست آمده است. نتایج نشان میدهد که راهنمای طراحی MPO تاحدی غیر محافظه کارانه است. برای ارزیابی تغییرات میانگین شاخص قابلیت اطمینان قبل و بعد از مقاوم سازی با ضرایب مقاومت مختلف، یک نسبت مقاومت ایمن معرفی شده است. مطالعه پارامتری این ضریب نشان میدهد که اگر تراز قابلیت اطمینان تیرهای بتن آرمه تقویت شده با تیرهای بتن آرمه مشابه تقویت نشده ثابت نگه داشته شود بایستی به ترتیب مقدار 89.0 و 81.0 به عنوان ضریب مقاومت برای تیرهای تقویت شده با دورپیچ کامل ونواری بکار برده شود.



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