ارزیابی ضرایب بزرگنمایی تغییرمکان پیشنهاد شده در آیین نامه ASCE7 و استاندارد 2800 – ویرایش چهارم – برای قاب‌‌های خمشی ویژه بتنی با و بدون دیواربرشی

نوع مقاله : پژوهشی اصیل (کامل)

نویسندگان
رضا رجبی سهیلی 1
الهام رجبی 2
یاسر گلستانی 1
1 دانشجوی کارشناسی ارشد، دانشکده مهندسی عمران، دانشگاه تفرش
2 استادیار، دانشکده مهندسی عمران، دانشگاه تفرش
10.22034/22.4.6
چکیده
معمولاً در آیین‌نامه‌های تدوین‌شده بر اساس شیوه‌ی «طراحی بر مبنای نیرو»، مقادیر بارهای جانبی ناشی از زلزله، توسط ضریب رفتار (R)، کاهش یافته و بنابراین تغییرمکان‌های جانبی حاصل از تحلیل استاتیکیِ خطیِ نیز، به صورت کاهش‌یافته نتیجه می‌گردند. از این رو لازم است که این تغییرمکان‌ها پس از تحلیل سازه، تحت بزرگنمایی قرار گرفته تا تخمینی از مقادیر واقعی این تغییرمکان‌ها حاصل شود. این عملیات در اغلب آیین‌نامه‌های لرزه‌ای، معمولاً به وسیله‌ی اعمال ضریبی تحت عنوان ضریب بزرگنمایی تغییرمکان (Cd)، صورت می‌پذیرد. بدین منظور در این مقاله، ضریب بزرگنمایی تغییرمکان (Cd) برای سیستم‌های باربر جانبی از نوع قاب خمشی بتن‌آرمه ویژه با و یا بدون دیوار برشی بتن‌آرمه، تحت ارزیابی واقع گردیده است. در این راستا، برای هر یک از سیستم‌های باربر جانبی یادشده، 3 عدد قاب ساختمانی 3، 7 و 11 طبقه در نظر گرفته شده است. این قاب­ها علاوه بر تحلیل‌های استاتیکی خطی، در معرض رکوردهای حوزه دور معرفی شده در دستورالعمل FEMA P695 تحت تحلیل دینامیکی خطی و دینامیکی غیرخطی تحت قرار گرفته­اند و در انتها نیز ضریب Cd برای هر کدام از قاب‌ها محاسبه و استخراج گردیده است. نتایج حاکی از آن است که مقادیر پیشنهادی آیین‌نامه‌های ASCE7-16 و استاندارد 2800 (ویرایش 4) برای ضریب یادشده در سیستم‌های باربر جانبی مذکور کافی نبوده و به منظور تخمین واقع‌‌گرایانه‌‌تری از عملکرد سازه در زلزله، مقادیر Cd بزرگتری تقاضا گردیده است. این مقادیر برای سیستم‌‌های باربر قاب خمشی بتن‌آرمه ویژه با و یا بدون دیوار برشی بتن‌آرمه پیشنهاد شده است.

کلیدواژه‌ها

موضوعات

عنوان مقاله English

Evaluation of Proposed Deflection Amplification Factor in ASCE7 and Standard No. 2800- 4th Version for Special Moment-Resisting Frame with/without Shear Wall

نویسندگان English

Reza Rajabi Soheyli 1
Elham Rajabi 2
Yaser Golestani 1
1 MSc Student, Department of Civil Engineering, Tafresh University, 39518-79611 Tafresh, Iran
2 Assistant Professor, Department of Civil Engineering, Tafresh University, 39518-79611 Tafresh, Iran
چکیده English

Response modification factors are used to reduce the lateral loads in "force-based design" method. Naturally the calculated lateral displacement (drift) of the structures in the linear static analyses is smaller than actual values. Hence, deflection amplification factor (Cd) is needed to consider a realistic estimation of nonlinear displacements. Most seismic design codes such as ASCE7 and standard No. 2800- 4th version propose this factor for different lateral bearing systems. This paper evaluates the proposed deflection amplification factor for dual system of special reinforced concrete moment-resisting frame with/without shear wall. For this purpose, a set of 2D reinforced concrete frames with 3, 7 and 11 story are designed based on standard No. 2800 (4th version) and implemented in Opensees software in each case without considering the soil- foundation- structure interaction. In this regard, beams and columns are modeled using concentrated plasticity method with “Elastic Beam Column Element” in the middle and “Zerolength Element” at the end of elements. Moreover, “SFI-MVLEM” element is used for modeling of shear walls. Nonlinear behavior in two ends of the beams and columns is assigned by “Modified Ibarra- Medina- Krawinkler Deterioration Model with Peak-Oriented Hysteretic Response” model which has been developed by Ibarra et al. (2005). This model is defined using the proposed equations by Haselto et al. (2007). Uniaxial behavior of steel reinforcements and concrete sections are simulated by Steel02 and ConcreteCM, respectively. Studied frames are verified using Hatzigeorgiou and Liolios (2010) and Liu et al. (2020) study for special moment-resisting frame with/without shear wall, respectively. In addition to linear static analysis (LSA), linear and nonlinear dynamic analyses (LDA and NDA) are applied to 3, 7 and 11 story frames with two lateral bearing systems. In this regard, 22 far-field ground motion records which have been introduced in FEMA P695 are used as seismic scenarios. These records are scaled based on Standard No. 2800 to have identical spectral acceleration with the design spectrum for the fundamental period (T) of each studied frames. For this purpose, each record is normalized to its peak ground acceleration and records are scaled so that the average acceleration spectrum of all records was above the design spectrum in 0.2T to 1.5T range. In order to evaluate the deflection amplification factor and Cd/R, maximum drift of roof and other stories is used for each frames due to concentration of structural damage in certain floors of a multi-story structures and, consequently, creating larger lateral displacements in those floors. The calculated Cd coefficients are compared to the proposed values in ASCE7 and standard No. 2800 (4th version) for all special reinforced concrete moment-resisting frames with/without shear wall. This comparison shows that the Cd coefficients which have been proposed in above-mentioned seismic design codes are not appropriate and more realistic estimate of the structural performance in earthquake has demanded larger Cd values. Moreover, Cd and Cd/R values are changed with the height of special reinforce concrete frames with/without shear wall. Finally, adequate values of deflection amplification factors are proposed for these frames with/without shear wall in this paper.

کلیدواژه‌ها English

deflection amplification factor
Special Moment-Resisting Frames
Special Shear Wall
Linear Dynamic Analysis
nonlinear dynamic analysis
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مهندسی عمران مدرس
دوره 22، شماره 4
خرداد و تیر 1401
صفحه 79-93