تعیین ضریب ایمنی جزئی (γM) مربوط به مشخصات مصالح بنایی تاریخی ایرانی با لحاظ‌نمودن عدم قطعیت

نوع مقاله : علمی - پژوهشی

نویسندگان

1 دانشجوی دکتری، دانشگاه سمنان، سمنان، ایران

2 استادیار مهندسی عمران، دانشگاه سمنان، سمنان، ایران

3 دانشیار مهندسی عمران، دانشگاه صنعتی امیرکبیر، تهران، ایران

چکیده

طبق تعریف آیین‌نامه یوروکد، γM ضریب ایمنی جزئی مربوط به مشخصات مصالح با لحاظ نمودن عدم قطعیت در هندسه و مدلسازی است که مقدار طراحی برای مشخصات مصالح از تقسیم مقدار واقعی مشخصات مصالح بر این ضریب مشخص می‌شود. در این تحقیق، مقادیر این ضریب جزیی مربوط به مشخصات مصالح بنایی تاریخی ایران، تعیین گردیده است. برای این منظور، رفتار نمونه‌های مختلف دیوارهای برشی بنایی (با ضخامت ثابت) تحت بارگذاری برشی درون‌صفحه‌ای و پیش‌فشار ثابت با چهار نسبت ابعادی ارتفاع به دهانه متفاوت و شش حالت مختلف از قیودات جانبی، ناشی از اثر دیوارهای جانبی و سقف، تحت تحلیل‌های غیرخطی پوش‌آور، با لحاظ نمودن اثر عدم قطعیت برای دو پارامتر مدول الاستیسیته مصالح و ضخامت دیوار، بصورت عددی مورد مطالعه قرار گرفت. نتایج این تحقیق نشان داد که با افزایش نسبت ابعادی، ظرفیت باربری برشی دیوارها کاهش و مقدار ضریب ایمنی جزئی γM افزایش می‌یابد، این درحالی است که با افزایش قیدهای مرزی ناشی از اثر دیوارهای جانبی و سقف، ظرفیت باربری جانبی دیوارها افزایش و مقدار ضریب ایمنی جزئی γM کاهش می‌یابد. در نهایت، ضریب جزیی γM با لحاظ نمودن عدم قطعیت، برای مشخصات مکانیکی مصالح بنایی تاریخی ایرانی در دیوارهای برشی در بازه 1/1 تا 8/1 تعیین گردید. تاثیر بیشتر مولفه‌ی افقی (سقف)، نسبت به وجود یک مولفه قائم (دیوار جانبی)، در مقیدترکردن دیوار برشی و افزایش ظرفیت برشی آن نیز در این تحقیق مشاهده گردید. هم‌چنین ملاحظه گردید که کاهش در سختی برشی اولیه دیوارها با افزایش نسبت ابعادی دیوار قابل ملاحظه بود، درحالیکه این پارامتر با تغییر در مولفه‌های جانبی قیودات مرزی دیوار تغییرات اندکی داشت.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Determination of Partial Safety Factors (γM) for Model Uncertainties for Persian Historical Masonry Materials

نویسندگان [English]

  • Mehrdad Ghamari 1
  • Mohammad Saeed Karimi 2
  • Abdulazim Amirshahkarami 3
1 PhD student, Faculty of Civil Engineering, Semnan University, Semnan, Iran Assistant Professor, Faculty of Civil Engineering, Semnan University, Semnan, Iran
2 Assistant Professor, Faculty of Civil Engineering, Semnan University, Semnan, Iran
3 Assistant Professor, Department of Civil & Environmental Engineering, Amirkabir University of Technology, Tehran
چکیده [English]

According to the Eurocode, the partial safety factor (γM) is a coefficient related to the material properties considering the uncertainties in geometry and modeling, which design value for the material properties are determined by dividing the actual value of the material properties by this coefficient. In this paper, determination of γM considering uncertainties for the Persian historical masonry shear wall was studied. To this aim, behavior of different specimens of masonry shear walls (with constant thickness) under in-plane shear loading and constant pre-compression with four different aspect ratios (height to length) and six different boundary constraints (under the effect of lateral walls and ceiling), by considering the uncertainty effect for two parameters of modulus of elasticity and thickness of wall were studied by the nonlinear pushover analyses. The results showed that by increasing the aspect ratio, the lateral shear strength of the walls decreases and γM is increased, whilst by increasing the boundary constraints, shear strength of the walls increases and γM decreases. The more impact of the horizontal component (ceiling) was observed, as compared to the vertical component in one direction, increases the boundary constraints and the lateral load-bearing capacity. It was also observed that the decrease in the initial shear stiffness of the walls was characterized by an increase in the wall aspect ratio, although this parameter changed slightly with changes in boundary constraints. In conclusion, the value of γM for the Persian historical masonry shear wall materials is proposed between 1.1 to 1.8.

کلیدواژه‌ها [English]

  • Masonry shear wall
  • Persian historical masonry
  • Uncertainty
  • Lateral constraints
  • nonlinear pushover analysis
  • Lateral load-bearing capacity
  • The partial safety factor (γM)
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