بررسی آزمایشگاهی تاثیر خروج ‌از‌ مرکزیت و نسبت پهنا ‌به‌ ضخامت مقاطع دستک‌های ‌قوسی فلزی بر رفتار چرخه‌ای

نوع مقاله : مقاله پژوهشی

نویسندگان

دانشکده مهندسی عمران، دانشگاه سمنان، سمنان، ایران

چکیده

این مقاله به معرفی دستک‌های قوسی فلزی به‌ عنوان روشی نوین در بهسازی لرزه‌ای قاب‌های بتن ‌آرمه می‌پردازد. در این راستا عواملی چون خروج ‌از ‌مرکزیت اولیه و نسبت پهنا به ضخامت مقاطع دستک‌های قوسی به ‌‌عنوان دو عامل موثر بر رفتار چرخه‌ای آن‌ها مورد ارزیابی قرار می‌گیرد. یک سری بارگذاری چرخه‌ای روی چهار نمونه آزمایشگاهی با مقاطع مستطیلی تکی و دوبل با مساحت و طول اسمی یکسان ولی با خروج ‌از‌ مرکزیت‌های مختلف 1/0 و 2/0 طول اسمی انجام گرفت. نتایج آزمایشگاهی نشان‌ دادند که نسبت‌های لاغری و پهنا به ضخامت نقش بسیار مهمی بر ‌عملکرد چرخه‌ای در فشار و حتی کشش ایفا کرده و با کاهش پتانسیل کمانش و افزایش امکان پلاستیک ‌شدن کامل مقطع، رفتار هیسترزیس مطلوب‌تری حاصل می‌گردد. بنابراین با کاهش50% هم‌زمان این دو نسبت، حداکثر مقاومت فشاری و کششی به ‌ترتیب تا 59% و 27% و انرژی تلف‌‌ شده و حداکثر نسبت میرایی ویسکوز به‌ ترتیب تا 152% و 14% افزایش یافتند. همچنین دستک‌های قوسی در ‌کشش و فشار از لحاظ مقاومت نهایی و سختی پلاستیک رفتار متفاوتی از خود نشان ‌‌دادند که این تفاوت با کاهش خروج ‌از‌ مرکزیت اولیه آشکارتر گردید. با افزایش خروج ‌از‌ مرکزیت محوری اولیه، تاثیر مساحت مقطع بر افزایش مقاومت فشاری و به‌ ویژه حداکثر مقاومت کششی کمتر شد. از طرفی با کاهش 50% آن و علیرغم کاهش 59% مساحت مقطع، مقدار مقاومت و سختی پلاستیک نهایی در‌کشش به ‌ترتیب تا 1/31 و 3/5 برابر افزایش‌ یافتند. همچنین نتایج این پژوهش برای تحقیقات بیشتر روی رفتار آزمایشگاهی اتصالات تیر-ستون بتن ‌آرمه استفاده خواهد ‌شد.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Experimental Study of Eccentricity and Width-to-Thickness Ratio Effects of Arched Steel Haunches on Cyclic Behavior

نویسندگان [English]

  • Ebrahim Emami
  • A. Kheyroddin
  • Omid Rezaifar
Department of Civil Engineering, Payame Noor University, Semnan, Iran
چکیده [English]

This paper introduces arched steel haunches (ASHs) as a novel technique in the seismic retrofitting of RC frames. In this regard, parameters such as ASH initial eccentricity and width-to-thickness ratio are evaluated as two factors affecting their cyclic behavior. A series of cyclic loading tests were performed on four specimens with single and double rectangular cross-sections and with the same nominal area and length, but with different eccentricities of 0.1 and 0.2 nominal length. Experimental results showed that the slenderness and width-to-thickness ratios play a significant role in the cyclic performance in compression and even tension, and by reducing the buckling potential and the cross-section reaching the fully plastic state, a more desirable hysteretic behavior is achieved. Therefore, with 50% reduction of these ratios simultaneously, the maximum compressive and tensile strength enhanced up to 59% and 27%, respectively, and the dissipated energy and the maximum viscosity damping ratio increased up to 152% and 14%, respectively. Also, the arched haunches showed different behavior in tension and compression for ultimate strength and plastic stiffness, which with decreasing the initial eccentricity, became more apparent. With increasing the initial eccentricity, the cross-sectional area effect on the increase of compressive strength and especially maximum tensile strength decreased. In addition, by reducing it by 50% and despite 59% reduction in cross-sectional area, the ultimate tensile plastic strength and stiffness increased up to 1.31 and 3.5 times, respectively. In addition, the obtained results will be used for further research on the experimental behavior of RC beam-column joints.

کلیدواژه‌ها [English]

  • Seismic retrofitting
  • Arched steel haunches
  • Cyclic performance
  • Overall buckling
  • Chord elastic stiffness

مراجع

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نشریه مهندسی عمران امیرکبیر
دوره 54، شماره 8
آبان 1401
صفحه 2851-2876

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