ارزیابی روش های اتصال داخلی غیر‌مستقیم مهاربندهای ضربدری فولادی به منظور مقاوم سازی قاب های خمشی بتن آرمه موجود

نوع مقاله : علمی - پژوهشی

نویسندگان

1 گروه مهندسی عمران، واحد سمنان، دانشگاه آزاد اسلامی، سمنان، ایران

2 استاد ممتاز، دانشکده مهندسی عمران، دانشگاه سمنان، سمنان، ایران

3 دانشیار، مرکز تحقیقات ژئوتکنیک لرزه‌ای و بتن توانمند، گروه مهندسی عمران، واحد سمنان، دانشگاه آزاد اسلامی، سمنان، ایران

چکیده

قاب های بتن آرمه غیر شکل پذیر معمولاً در ساختمان های قدیمی بسیاری از مناطق جهان یافت می شوند. این سازه ها که عموماً برای اثرات بار ثقلی طراحی شده اند، از مقاومت جانبی و شکل پذیری محدودی برخوردار بوده و تحت حرکات زمین تمایل به جابجایی جانبی بیش از حد یک طرفه و مکانیسم طبقه نرم دارند. این مطالعه بر روی مقاوم سازی یک قاب بتن آرمه موجود با استفاده از مهاربندهای ضربدری فولادی به روش اتصال داخلی غیر‌مستقیم متمرکز بوده و هدف اصلی آن، مطالعه تحلیلی و بررسی رفتار و پاسخ کلی نمونه قاب های آسیب پذیر مقاوم سازی شده در مقیاس بزرگ است. به این منظور از یک مطالعه آزمایشگاهی مرتبط برای اعتبار سنجی مدل سازی عددی صورت گرفته در نرم افزار آباکوس استفاده و سپس نمونه مرجع با قرار دادن قاب فولادی ضربدری مهاربندی شده و شیوه های متفاوت اتصال داخلی غیرمستقیم پیشنهادی مقاوم سازی گردیده و در مطالعات پارامتریک مجزا، تاثیر نوع پروفیل قاب فولادی، نوع اتصال و استفاده همزمان از گروت با مقاومت بالا در نواحی مرزی بین قاب فولادی و قاب بتن آرمه مورد بررسی قرار گرفته است. نتایج نشان می دهد که استفاده از مهاربند ضربدری فولادی بصورت غیر‌مستقیم در قاب های بتن آرمه آسیب پذیر، بطور متوسط باعث افزایش3.7 و 2.8 برابری سختی و مقاومت جانبی و هم چنین کاهش50 درصدی تغییر مکان نهایی و دریفت می شود. ضمن اینکه مهاربند به عنوان سیستم دفاعی اول در برابر بارهای جانبی، مانند فیوز عمل کرده و با جاری شدگی خود میزان استهلاک انرژی را افزایش می دهد. هم چنین با کاهش تنش های ناشی از بار جانبی در محل چشمه اتصال، مفصل پلاستیک را از این ناحیه دور می کند.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Strengthening of RC moment resisting frames using indirect internal connection of X-steel bracing

نویسندگان [English]

  • Siavash sadeghi nezhad 1
  • Ali Kheyroddin 2
  • Alireza Mortezaei 3
1 faculty of civil engineering-Islamic Azad university-Semnan Branch
2 Professor, Faculty of Civil Engineering, Semnan University, Semnan, Iran
3 Associate Professor, Seismic Geotechnical and High Performance Concrete Research Centre, Civil Engineering Department, Semnan Branch, Islamic Azad University, Semnan, Iran
چکیده [English]

Non-ductile reinforced concrete frames are commonly found in older buildings in many parts of the world. These structures designed for gravity loads, have limited lateral strength and ductility, are prone to excessive one-way lateral movement and soft-story mechanism. This paper focuses on the retrofit of an existing reinforced concrete frame, using steel X-braces by indirect internal connection method. The main purpose is the analytical study of general behavior and response of large scale vulnerable frames. An experimental study was used to validate the numerical modeling performed in ABAQUS. Next the base samples were retrofitted with X-braces and four proposed indirect internal connection methods. Furthermore, in a separate parametric studies, the effect steel frame profile type, connection type and use of high strength grout in the boundary zones between steel and reinforced concrete frames were investigated. The results indicated that the stiffness and bearing capacity of the reinforced concrete frame by using steel X-braces increases up to 3.7 and 2.8 times, respectively. It also reduces the final displacement and drift by 50%. Moreover, bracing acts like the first defense system against lateral loads, such as structural fuse with its yield, increases the amount of energy dissipation. It also removes the plastic hinges by reducing the ultimate displacement and stress of lateral load in the panel zone.

کلیدواژه‌ها [English]

  • reinforced concrete frame
  • steel X-brace
  • strengthening
  • finite Element analysis
  • Indirect connection
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