تخمین پاسخ ستون های بتن مسلح تحت بارگذاری انفجار به روش تک درجه آزادی معادل و مقایسه ی آن با روش اجزای محدود

نوع مقاله: علمی - پژوهشی

نویسندگان

1 استادیار، دانشکده فنی و مهندسی، دانشگاه کردستان، سنندج، ایران

2 دانشجوی دکتری مهندسی سازه، دانشکده فنی و مهندسی، دانشگاه کردستان، سنندج، ایران

چکیده

در تحلیل و طراحی بسیاری از سازه­های بتن مسلح در برابر انفجار از تحلیل تک­درجه آزادی (SDOF) استفاده می­شود. عموماً، در این روش تحلیل، پاسخ خمشی اعضا در نظر گرفته می­شود اما در اعضایی که دارای بار محوری باشند لنگرهای ثانویه (P-δ) نیز اهمیت پیدا می­کند. در زمان وقوع انفجار در داخل و یا نزدیکی ساختمان­های بتن مسلح ستون­های آن در معرض فشار جانبی ناشی از موج انفجار قرار می­گیرد. در این ستون­ها، که گاهاً بارهای محوری قابل توجهی را تحمل می­کنند، نادیده گرفتن لنگرهای P-δ تحت بارگذاری جانبی انفجار می­تواند ریسک بالایی به همراه داشته باشد. در این مقاله به توصیف روشی ساده برای درنظرگرفتن پاسخ P-δ و هم­چنین اثرات نرخ کرنش (که در بارگذاری­های دینامیکی شدید بسیار اهمیت پیدا می­کند) در تحلیل SDOF  ستون­های بتن مسلح تحت اثر همزمان بار محوری فشاری و بار جانبی ناشی از انفجار پرداخته شده است. پاسخ­های حاصل از روش SDOF با تحلیل اجزای محدود با استفاده از نرم­افزار LS-DYNA مقایسه می­شود. در اینجا، در طی مراحل حل معادلات حرکت سیستم SDOF  لنگرهای ثانویه به روش بار جانبی معادل و اثرات نرخ کرنش به صورت ضرایب افزایش دینامیکی وارد محاسبات شده است. مطابق با نتایج حاصل روش معرفی شده مطابقت خوبی با نتایج به دست آمده از نرم­افزار اجزای محدود دارد. به طورکلی، نتایج حاصل از روش SDOF معرفی شده محافظه کارانه است و برای اهداف طراحی و ارزیابی اولیه ستون­های بتن مسلح تحت انفجار روش مناسبی است.  

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Estimation of RC columns’ response under the effect of lateral blast loading by SDOF method and comparison with FEM

نویسندگان [English]

  • Mohammad Esmaeil Nia Omran 1
  • Somayeh Mollaei 2
1 Assistant professor, Department of Civil Engineering, University of Kurdistan, Sanandaj, Iran
2 PhD student, Department of Civil Engineering, University of Kurdistan, Sanandaj, Iran
چکیده [English]

In most of the structural blast-resistant designs and analysis single degree of freedom (SDOF) method is used. Generally, for this method flexural response of the structural members is considered but in axial loaded members, secondary moments (P-δ effects) are also very important. In the case of columns of building structures, which mostly bear significant axial loads, ignoring P-δ effects under lateral blast loading can be very risky. This paper describes a simple way for taking into account P-δ effects and also the effects of high strain rates (which is very important in severe dynamic loading) in SDOF analysis of reinforced concrete columns under simultaneous axial load and lateral blast loading. The resulting responses are compared with explicit finite element analysis using LS-DYNA hydro-code. Proposed SDOF equation of motion is numerically calculated and secondary moment and high strain rate effects are included within the calculation procedure. Secondary moments due to P-δ effects have been considered as equivalent lateral load and strain effects are introduced to the model by dynamic increasing factors for concrete and steel materials. Based on the main results, estimated response of RC column under blast loading using SDOF method has acceptable accuracy compared to LS-DYNA analysis results.   

کلیدواژه‌ها [English]

  • SDOF method
  • axial force
  • Blast Loads
  • RC Column
  • LS-DYNA software

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