بررسی تأثیر نرخ بارگذاری و مقاومت فشاری بر مودهای شکست خمشی تیر بتن مسلح تحت بار ضربه به روش آنالیز عددی

رحمتی علائی, احمد; خاتمی, سید محمد حسین

doi:10.48301/kssa.2025.476674.2985

بررسی تأثیر نرخ بارگذاری و مقاومت فشاری بر مودهای شکست خمشی تیر بتن مسلح تحت بار ضربه به روش آنالیز عددی

نوع مقاله : مقاله پژوهشی (کاربردی)

نویسندگان

احمد رحمتی علائی ¹

سید محمد حسین خاتمی ²

¹ گروه مهندسی مکانیک، دانشگاه ملی مهارت، تهران، ایران

² گروه مهندسی عمران، دانشگاه ملی مهارت، تهران، ایران

10.48301/kssa.2025.476674.2985

چکیده

در این پژوهش تأثیر نرخ بارگذاری و مقاومت فشاری بر مودهای شکست خمشی تیر بتن مسلح تحت بار ضربه‌ای سقوط آزاد با استفاده از شبیه‌سازی‌های عددی مبتنی بر نمونه‌های آزمایشگاهی تحلیل و ارزیابی شده است. مطابق نتایج به دست آمده در آنالیز عددی، تغییر شکل دهانه میانی تیر بتن مسلح در مقایسه با آزمایش ضربه سقوط آزاد، کمتر از 8 % (معادل mm 5/0) اختلاف دارد؛ بنابراین مدل عددی که با استفاده از کد المان محدود LS-DYNA توسعه ‌یافته است می‌تواند با دقت قابل قبول برای پیش‌بینی میزان آسیب‌پذیری تیر بتنی و الگوی ترک‌های ایجاد شده به کار گرفته شود. در نمونه بتن مسلحS1616 همسانی مودهای شکست خمشی مطابق کرنش پلاستیک مؤثر مشاهده می‌گردد. در این مطالعه 5 نرخ بارگذاری متفاوت کم تا زیاد شامل m/s 2، m/s 4، m/s 6، m/s 8 و m/s 10 برای مقاومت فشاری MPa 32، MPa 42 و MPa 52 آنالیز شده است. نتایج به دست آمده نشان می‌دهد در ‌ازای هر Mpa 10 افزایش مقاومت فشاری بتن، بیشینه تغییر شکل تیر بتن مسلح به میزان تقریباً ۱۰% کاهش می‌یابد. در نرخ بارگذاری بسیار زیاد (m/s 10)، نیروی ضربه در مقاومت فشاری بین MPa 32 تا Mpa 52 حدود ۳۱ % افزایش می‌یابد. به علاوه بیشینه تغییر شکل تیر با افزایش قطر میلگردهای فولادی در شرایط بحرانی ضربه تاثیر چندانی نخواهد پذیرفت.

کلیدواژه‌ها

تیر بتن مسلح

مودهای شکست خمشی

نرخ بارگذاری

مقاومت فشاری

آنالیز المان محدود

موضوعات

مهندسی عمران

عنوان مقاله English

Investigating the effect of loading rate and compressive strength on flexural failure modes of RC beam under impact load by numerical analysis method

نویسندگان English

Ahmad Rahmati Alaei ¹

Seyed Mohammad Hosein Khatami ²

¹ Department of Mechanical Engineering, Technical and Vocational University (TVU), Tehran, Iran.

² Department of Civil Engineering, Technical and Vocational University (TVU), Tehran, Iran.

چکیده English

In this research, the effect of loading rate and compressive strength on flexural failure modes of reinforced concrete (RC) beams under free fall impact loads is analyzed and evaluated using numerical simulations based on experimental tests. According to the numerical results, the deformation of the middle of the reinforced concrete beam compared to the free fall impact test has a difference of less than 8% (equivalent to 0.5 mm); therefore, the numerical model developed using LS-DYNA finite element code can be used with acceptable accuracy to predict the damage to the RC beam and crack patterns. In the S1616 sample test, the similarity of the bending failure modes is observed according to the effective plastic strain. In this study, 5 different loading rates from low to high, including 2 m/s, 4 m/s, 6 m/s, 8 m/s, and 10 m/s, are analyzed for compressive strengths of 32 MPa, 42 MPa, and 52 MPa. The results show that for every 10 MPa increase in concrete compressive strength, the maximum deflection of the RC beam decreases by approximately 10%. At a very high loading rate (10 m/s), the impact force increases by about 31% in the compressive strength between 32 MPa and 52 MPa. Furthermore, for critical impact conditions, increasing the diameter of steel rebars does not significantly affect the maximum deflection.

کلیدواژه‌ها English

Reinforced Concrete (RC)

Bending Failure Modes

Loading Rate

Compressive Strength

Finite Element Analysis (FEA)

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