روش ساده آنالیز کوتاه شدگی وابسته به زمان ستون در سازه های قابی بتن آرمه

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشجوی دکتری سازه

2 دانشکدة مهندسی عمران، دانشگاه سمنان، سمنان، ایران

چکیده

کوتاه شدگی تجمعی ستون‌ها در آنالیزهای یک مرحله‌ای متداول سازه، مهمترین شاخصه‌ای است که غفلت از رفتار واقعی ستون‌ها، که تنها با اعمال مرحله ای بارهای ثقلی و لحاظ کرنش‌های غیر الاستیک دراز مدت بتن حاصل می‌شود، درپی خواهد داشت. از این رو، توجه به تطابق طراحی سازه‌های بلند بتن آرمه و مراحل عملی اجرا، از طریق آنالیز غیر خطی مرحلهای با در نظر گرفتن رفتار دراز مدت بتن، همواره در سالهای اخیر مورد توصیه اکید پژوهشگران بوده امشخصات تا بدین وسیله از اثرات نا مطلوب سازهای احتمالی مانند اضافه لنگرهای اعمالی به اعضای افقی ناشی از تغییر شکل‌های محوری متفاوت اعضای مجاور و گسترش ترک در اعضای غیر سازهای در پانل‌های با نشستهای ثقلی نا همگون و عدم استفاده از ظرفیت در نظر گرفته شده در طراحی اعضای سازه جلوگیری شود. در این مقاله با انجام مدل‌سازی و آنالیزهای غیرخطی مرحله‌ای گسترده بر روی سازه‌هایی با مشخصات هندسی مختلف، روابط تجربی بسیار ساده جهت تخمین کوتاه شدگی ستون‌ها ناشی از خزش، آبرفتگی و تغییرات زمانی مدول الاستیسیته بتن، به گونه‌ای که مستقل از پارامترهای مرسوم روش CEB-FIPدر تخمین کرنش‌های محوری مذکور باشد، ارائه شده است. نتایج حاصل از صحت سنجی روابط پیشنهادی نشان از انطباق بسیار مطلوب تمامی روابط پیشنهادی تا 30طبقه و نیز صحت رابطه پیشنهادی آبرفتگی حتی برای سازه‌های قابی بلندتر از محدوده مورد بررسی تحقیق حاضر دارد.

کلیدواژه‌ها


عنوان مقاله [English]

A New Simplified Method of Time-dependent Column Shortening Analysis in Concrete Moment Frames

نویسندگان [English]

  • M. jalilzadeh afshari 1
  • A. Kheyroddin 2
1 Faculty of Civil Engineering, Semnan University, Semnan, Iran
2 Faculty of Civil Engineering, Semnan University, Semnan, Iran
چکیده [English]

Excessive column shortening in conventional one-step analyses is one of the most important aftereffects of ignoring the real behavior of concrete columns. This real behavior could only be achieved by staged application of gravity loads considering the long-term inelastic strains of concrete. Thereupon, consideration of adaptation between high-rise reinforced concrete structures’ design and practical stages of construction has always been staunchly held forth by researchers. Neglecting the fact above may lead to serious incorrect outcomes of analyses especially in high-rise structures. Some of these adverse structural effects are extra induced bending moments in beams, expansion of progressive cracks in second or non-structural elements, and wasting the intended capacity for structural elements in the design stage. This paper deals with comprehensive nonlinear staged analyses of structures with various geometrical specifications and represents simple empirical equations to evaluate column shortening caused by creep, shrinkage, and time changes of modulus of elasticity in such a way that the proposed relations could be independent of conventional variables of CEB-FIP code. Results of validation process show high conformity of all proposed equations for up to 30 floors and also demonstrate the accuracy of proposed shrinkage relation even for the structures higher than the aforementioned limit.

کلیدواژه‌ها [English]

  • Nonlinear Sequential analysis
  • Conventional Analysis
  • Column shortening
  • Creep
  • Shrinkage
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