مدل خرپایی جهت تخمین مقاومت برشی اتصالات تیر به ستون خارجی بتن مسلح فاقد آرماتور عرضی

نوع مقاله : علمی - پژوهشی

نویسندگان

1 کارشناس ارشد گرایش سازه، دانشگاه اراک، اراک، ایران

2 استادیار، پژوهشکده فناوری‌های نوین، گروه مهندسی عمران، دانشکدة فنی مهندسی، دانشگاه اراک، اراک، ایران

3 گروه مهندسی عمران، دانشگاه اراک، اراک، ایران

چکیده

این پژوهش، یک رابطه جدید براساس مدل خرپایی به منظور محاسبه مقاومت برشی اتصالات تیر به ستون خارجی بتن مسلح فاقد آرماتور عرضی در ناحیه اتصال ارائه می‌نماید. به منظور تحلیل و بررسی نواحی ناپیوسته از لحاظ بارگذاری و هندسی مثل تیرهای عمیق، کربل‌ها و اتصالات تیر به ستون استفاده از تئوری تیر معمول براساس فرضیه برنولی نامناسب بوده و بایستی از مدل خرپایی بهره گرفت. مدل خرپایی براساس جریان نیروها و جهات تنش‌های اصلی، ناحیه ناپیوسته عضو را با استرات‌های بتنی و تای‌های فولادی که در گره به یکدیگر متصل می‌گردند؛ به شکل یک خرپا، ایده‌آل می‌نماید. براساس بهینه‌سازی توپولوژی صورت گرفته به منظور تعیین جهات تنش‌های اصلی ناحیه اتصال؛ مکانیزم اصلی انتقال برش در اتصالات تیر به ستون خارجی بتن مسلح فاقد آرماتور عرضی ، مکانیزم استرات قطری می‌باشد. بنابراین مدل خرپایی پیشنهادی از یک استرات قطری بتنی از نوع بطری شکل تشکیل می‌گردد. دقت رابطه پیشنهادی با مقایسه مقاومت برشی 20 اتصال موجود در پژوهش‌های تجربی پیشین که براساس معیارهای منطقی انتخاب شده‌اند، کنترل شده است. رابطه پیشنهادی با درنظرگیری پارامترهای مؤثر بر رفتار اتصالات خارجی مثل مقاومت فشاری مشخصه بتن، درصد و مقاومت آرماتور طولی کششی تیر، آرماتورهای میانی ستون و نسبت ابعاد اتصال قادر به تخمین مقاومت برشی اتصالات تیر به ستون خارجی بتن مسلح فاقد آرماتور عرضی در ناحیه اتصال با دقت مناسب می‌باشد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Strut and tie model for estimating shear strength of RC exterior beam-column joints without transverse reinforcement

نویسندگان [English]

  • Reza Mashhadi 1
  • Mohammad Ali Dastan Diznab 2
  • Seyed Hamid Hashemi 3
1 Master of science of structural engineering, Civil Engineering Department, Arak University, Arak, Iran
2 Institute of advanced technology, Civil Engineering Department, Arak University, Arak, Iran
3 Assistant Professor of Civil Engineering Department, Arak University, Arak, Iran
چکیده [English]

A new formula based on strut and tie model to determine the shear strength of exterior beam-column joints without transverse reinforcement (stirrup) in the joint region under monotonic and seismic lateral loading is proposed in this paper. Based on the accomplished topology optimization to determine directions of the principal stresses of the joint region, the main shear transfer mechanism in beam-column joints without transverse reinforcement in the joint region is diagonal strut mechanism; therefore, the proposed strut and tie model is made up of a concrete bottle-shaped diagonal strut. Formulae available in published literature for calculating the diagonal strut angle of inclination was checked by finite element analysis results of two exterior joints, the results indicate that all formulae have good agreement. Various experimental data set of this kind of joints are collected from previous literature based on consistent and specified criteria for data selection. The accuracy of the proposed procedure and two approaches of determining the diagonal strut width was checked by comparing calculated shear strengths with experimental data. Based on the two introduced approaches for calculating the diagonal strut width, approach 1 which does not take into account the column axial load, has the best performance in the proposed model. The proposed formula, in addition to the specified compressive strength of concrete which is included in Iranian and American concrete codes, considers other effective parameters on exterior joints behavior such as the beam longitudinal tension reinforcement ratio and its strength, the intermediate column bars and the joint aspect ratio. Therefore, the proposed formula is able to estimate accurately the shear strength of exterior beam-column joints without transverse reinforcement in the joint region.

کلیدواژه‌ها [English]

  • Exterior beam-column joints
  • Transverse reinforcement Topology optimization
  • Strut and Tie Model
  • Diagonal strut
  • Shear strength
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