تاثیر درجات آزادی بر ضریب رفتار قاب‌های خمشی بتن آرمه دارای دیوار برشی فولادی نازک

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشگاه سمنان

2 عضو هیات علمی دانشگاه سمنان

چکیده

ضریب رفتار در اثر شکل‌پذیری (Rμ)، مقاومت جانبی سازه یکدرجه آزادی (SDOF) را طوری تنظیم می‌کند که نیاز شکل‌پذیری به یک مقدار شکل‌پذیری هدف معین محدود گردد. روش‌های موجود در آیین‌نامه‌های لرزه‌ای جهت محاسبه ضریب رفتار سازه چند درجه آزادی (MDOF) به نحوی پایه ریزی شده است که در راستای کاهش اثر ورود نیروی برش پایه به ناحیه غیرالاستیک، از نتایج Rμ استفاده گردد. این درحالی است که اثرات مدلسازی سازه به صورت MDOF می‌تواند بر ضریب رفتار سازه MDOF اثر داشته و به کمک Rμ نیازمند اصلاحاتی می‌باشد. به همین دلیل در این پژوهش دو ضریب کاهش مقاومت در اثر شکل‌پذیری (Rμ) و نسبت تغییرشکل غیرالاستیک به الاستیک (CR) در سازه SDOF برای مؤلفه‌های موازی و عمود برگسل زلزله حوزه نزدیک و دور از گسل محاسبه شده‌اند. همچنین CR بدست آمده با ضریب اصلاحی C1 پیشنهادی FEMA440 مقایسه و ضریب بزرگنمایی تغییرمکان به ضریب رفتار برای سطوح مختلف شکل‌پذیری محاسبه شده است. در پایان این پژوهش پس از بررسی اثرات غیر خطی سازه‌ی SDOF از طریق ضرایب Rμ پرداخته و با احتساب اثر مودهای بالاتر، این ضرائب را برای سازه‌های MDOF اصلاح می‌نماییم و رابطه‌ای برای محاسبه آن پیشنهاد می‌گردد. نتایج بدست آمده نشان داد که Rμ ناشی از زلزله حوزه نزدیک می‌تواند با مقدار متناظر حاصل از زلزله دور تفاوت داشته باشد. همچنین CR چندان به نوع رکورد وابسته نبوده و با افزایش دوره تناوب اصلی سازه به یک همگرا می‌شود. همچنین ضریب اصلاحی با افزایش دوره تناوب اصلی سازه و افزایش تقاضای شکل‌پذیری، افزایش می‌یابد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Effects of Freedom Degrees on Behavior Factor in Reinforced Concrete Moment Resisting Frames with Steel Plate Shear Wall

نویسندگان [English]

  • seyyed reza salim bahrami 1
  • majid gholhaki 2
1 Semnan university
چکیده [English]

The influence of the strength reduction factor due to nonlinear behavior (Rμ) on the lateral strength of Single-Degree-Of-Freedom (SDOF) structures causes to limit the displacement ductility demand to the predetermined maximum tolerable ductility. In addition, Rμ is used for determining the behavior factor in Multi-Degree-Of-Freedom (MDOF) structures. Following this, in this paper, Rμ and the inelastic displacement ratio (CR) for equivalent SDOF systems under strike[1]parallel (NF-SP) and strike-normal (NF-SN) components of near-field ground motion, and also far[1]field (FF) ground motion were assessed. Furthermore, CR obtained by this study was compared with C1 proposed by FEMA440. The deflection amplification factor-to-behavior factor ratio (Cd/Ru) for different ductility levels was computed. After evaluating the nonlinear effects of SDOF structures based on Rμ factors, these factors for MDOF structure were modified considering higher mode effects, and a simplified practical expression was proposed to estimate the base shear modification factor. The results indicated that Rμ, corresponds to near and far-field ground motions can be different. In addition, CR does not depend on the type of earthquake, and it converges to 1 by increasing the period of vibration. In addition, the modification factor can be increased with period and ductility demand.

کلیدواژه‌ها [English]

  • behavior factor
  • Modification Factor
  • SDOF Structure
  • MDOF
  • Base Shear
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