شبیه‌سازی رفتار خمشی بتن‌های الیافی با استفاده از اجزای ‌محدود – لنگر انحنای مقطع

نوع مقاله: مقاله پژوهشی

نویسندگان

دانشکده فنی مهندسی، دانشگاه قم.

10.22091/cer.2019.3907.1137

چکیده

بتن مسلح الیافی، عمدتا به واسطه رفتار خود در ناحیه کششی ترک خورده، که به آن رفتار نرم‌شوندگی کششی گفته می‌شود، متمایز می‌گردد. محققان مطالعات بسیاری بر روی این رفتار صورت داده و مدل‌های نرم‌شوندگی بسیاری ارائه کرده‌اند. با توجه به پیچیدگی‌های انجام آزمایش مستقیم، مبنای ارائه‌ نرم‌شوندگی، در بسیاری از تحقیقات تحلیل معکوس یک مقطع خمشی است. عمدتا این تحلیل با فرضیات ساده‌کننده انجام شده است. در این تحقیق، یک روش جدید ترکیبی از اجزای‌ محدود و لنگر- انحنا ارائه شده است. در این مطالعه، رفتار مقطع تیر مستطیلی تحت آزمایش خمش سه نقطه‌ای با استفاده از روش اجزای ‌محدود و به‌کارگیری روش طول کمان استوانه‌ای مورد بررسی قرار گرفته است. در این روش، اثرات غیرخطی در المان بحرانی، در هر مرحله با روابط لنگر– انحنا به روز شده و در تحلیل اجزای محدود اعمال می‌گردد. همچنین، این مطالعه، مقایسه‌ای بین چهار مدل نرم‌شوندگی کششی شامل مدل‌های ثابت، خطی، نمایی و دوخطی در رفتار خمشی مقطع مستطیلی را ارائه می‌دهد. این روش با برخی از نتایج آزمایشگاهی اعتبارسنجی شده است. نتایج نشان دهنده این است که این مدل‌ها برای بتن‌های با نرم‌شدگی تنشی کاهشی و کم الیاف نتیجه خوبی در بر دارد. همچنین با توجه به نتایج، توصیه می‌شود برای ارزیابی رفتار نمونه‌های الیافی که نرم‌شدگی در آنها قابل‌ملاحظه نمی‌باشد، در توسعه روابط لنگر- انحنا از توزیع ترک بازشدگی با منحنی‌های درجه 2 یا شبیه آن استفاده شود.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

New Method for Simulation the Flexural Behavior of Fiber Reinforced Concretes With Combining the Finite Element and Section Moment Curvature

نویسندگان [English]

  • Boshra Gilak
  • Mahdi Sharifi
  • Ahmad Mobinipour
Civil Engineering Department, University of Qom, Qom, Iran
چکیده [English]

Fiber reinforced concrete in tension is categorized based on tension softening behavior. Wide researchers have been studied this behavior and presented many tension softening models. With regard to the difficulties in direct tension test, tension softening diagram will be obtained a base on reverse analysis of flexural or split wedge test. The result of the inverse analysis method is mainly affected by applied assumptions. In this research, a new method which combines the finite element and section moment-curvature relations is presented. This method is called FE-SMC. In this study, the three-point bending test has been stimulated by this method. In each step of loading, the nonlinearity of cracked section properties have been calculated with moment-curvature relationships and the parameters have been updated in FE. The arc length method has been used for iterations solution. Finally, this method is validated with some experimental test results. The results show that FE-SMC method show desirable result for low-fiber content with descending tension softening diagram. Also using this method in some experimental results with constant tension softening or hardening behavior, do not meet the required fitting criteria and show deficiency in applied assumption and need to modifications.

کلیدواژه‌ها [English]

  • Fiber Reinforced Concrete
  • Tension Softening
  • Three-point/Four-point bending Test
  • Finite element method
  • sectional moment-curvature analyze
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