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مهندسی عمران مدرس، جلد ۲۵، شماره ۶، صفحات ۰-۰
عنوان فارسی ارزیابی روش‌های مقاوم‌سازی دال بتنی در برابر بار انفجار برای اجتناب از شکست ترد
چکیده فارسی مقاله دال‌های بتنی که تحت‌تأثیر انفجارهای حوزه نزدیک قرار می‌گیرند، معمولاً متحمل شکست ترد می‌شوند. ازجمله خرابی‌های ترد رایج می‌توان به شکست‌هایی نظیر scabbing وspalling اشاره کرد. شکست ترد علاوه بر اینکه موجب پاسخ غیرقابل‌انعطاف و شکننده سازه و سبب آسیب‌های بیشتر به سازه می‌شود، می‌تواند تولید ترکش‌های کوچک و بزرگ و با سرعت‌های بالا کند؛ بنابراین برای طراحی دال بتنی تحت بار انفجار، استفاده از روش‌هایی که منجر به جلوگیری یا کاهش شکست‌های ترد و یا تبدیل آن‌ها به شکست‌های انعطاف‌پذیر می‌شوند، ضروری است. فلذا در این مطالعه، با معرفی یک روش عددی با استفاده از نرم‌افزار المان محدود LS-DYNA و پس از اطمینان از صحت مدل‌های عددی با مقایسه با تحقیقات معتبر، به مقاوم‌سازی دال‌های بتنی متعارف با استفاده از میلگردگذاری Lacing، تعبیه ورق فولادی، استفاده از شبکه سیمی فولادی و به‌کارگیری دال بتنی فوق توانمند پرداخته شده است. طبق تجزیه‌وتحلیل نتایج مربوط به رفتار 5 نوع دال تحت بارگذاری انفجاری مشابه، دال‌های بتن فوق توانمند نسبت به سایر دال‌های بتنی خیز و خرابی کمتری داشته و دال‌های بتنی متعارف در مقایسه با سایر دال‌های بتنی متحمل خیز و خرابی بیشتری می‌شوند. بهترین ابعاد در کاهش خرابی دال‌های بتن مسلح تقویت‌شده با ورق فولادی و شبکه سیمی، زمانی است که سطح ورق فولادی و شبکه سیمی از ابعاد سطح خرابی دال مسلح اولیه بزرگ‌تر باشد. وجود شبکه سیمی فولادی باعث کاهش محسوس خرابی دال نسبت به دال متعارف شد. این کاهش خرابی بین 78% الی 89% مشاهده شد. میزان اثرگذاری شبکه سیمی فولادی در کاهش خرابی، زمانی قابل‌ملاحظه‌تر بود که ابعاد شبکه بزرگ‌تر از ابعاد خرابی دال متعارف باشد. در این حالت، میزان کاهش خرابی بین 82% الی 89% به دست آمد. وجود ورق فولادی با ابعادی بزرگ‌تر از ابعاد خرابی اولیه و در وجه پشتی دال، می‌تواند باعث کاهش محسوس خرابی دال نسبت به دال متعارف، بین 58% الی 83% شود.
 
کلیدواژه‌های فارسی مقاله دال بتنی،شکست ترد،انفجار حوزه نزدیک،LS_DYNA
عنوان انگلیسی Evaluation of retrofit Methods for Concrete Slabs Against Blast Loads to Avoid Brittle damage
چکیده انگلیسی مقاله Concrete slabs subjected to near-field explosion loading often fail in a brittle manner. Common failure types include spalling and scabbing. Brittle failure leads to an inflexible and brittle structural response, producing small and large fragments that can be extremely dangerous due to their high velocities. Therefore, designing concrete slabs for explosive loading requires methods that either prevent or mitigate brittle failures or transform them into ductile failures. This study validates numerical models using LS-DYNA finite element software and compares them with reputable research. Simulations of concrete slabs were conducted using conventional methods, reinforced concrete slabs with steel plates, reinforced concrete slabs with wire mesh, and ultra-high-performance concrete (UHPC) slabs. The analysis of five slab types under similar explosion loading reveals that UHPC slabs exhibit less deflection and damage compared to other types, while conventional concrete slabs experience greater deflection and damage. The optimal reduction in damage for reinforced concrete slabs occurs when a steel plate measuring 2 by 4.2 meters and 0.5 centimeters thick is applied to the backside. Additionally, using wire mesh dimensions 25% larger than the initial slab damage yields the best performance. A comparative analysis of explosion-induced damage across different slab types indicates that reinforced concrete slabs with a 0.5-centimeter thick steel plate exhibit the largest damage area (8m2); whereas UHPC slabs show no damage, resulting in the smallest damage area. Further investigations into the dynamic response of these slabs demonstrate that advanced materials and reinforcement techniques significantly enhance their resilience against explosive forces. This study emphasizes the importance of innovative design strategies in civil engineering, highlighting that the adoption of UHPC slab minimizes structural damage and improves safety in high-risk environments. These findings underscore the necessity of incorporating modern materials and methodologies in protective structure design, ensuring better performance and longevity under extreme loading conditions. A comparative analysis of various methods for strengthening concrete slabs using identical materials shows that UHPC slabs outperform others in reducing deflection and failure. This illustrates their exceptional ability to withstand explosive dynamic loads. However, the primary limitation of UHPC slabs is their high cost and complexity of implementation. Reinforcement with steel sheets has proven more effective than wire mesh in minimizing deflection. In models reinforced with 0.5 cm steel sheets, deflection was reduced by 50% compared to conventional concrete slabs. The slabs reinforced with wire mesh demonstrated a significant decrease in failure rates compared to conventional slabs, with reductions ranging from 75% to 80% across various reinforcement methods using the same materials. Conversely, some models reinforced with steel sheets exhibited increased failure rates. The findings indicate that, in most cases, slabs with greater flexibility, such as those reinforced with wire mesh, sustained less damage. This can be attributed to the enhanced flexibility and ductility of wire mesh-reinforced slabs compared to those reinforced with steel sheets.
Concrete slabs subjected to near-field explosion loading often fail in a brittle manner. Common failure types include spalling and scabbing. Brittle failure leads to an inflexible and brittle structural response, producing small and large fragments that can be extremely dangerous due to their high velocities. Therefore, designing concrete slabs for explosive loading requires methods that either prevent or mitigate brittle failures or transform them into ductile failures. This study validates numerical models using LS-DYNA finite element software and compares them with reputable research. Simulations of concrete slabs were conducted using conventional methods, reinforced concrete slabs with steel plates, reinforced concrete slabs with wire mesh, and ultra-high-performance concrete (UHPC) slabs. The analysis of five slab types under similar explosion loading reveals that UHPC slabs exhibit less deflection and damage compared to other types, while conventional concrete slabs experience greater deflection and damage. The optimal reduction in damage for reinforced concrete slabs occurs when a steel plate measuring 2 by 4.2 meters and 0.5 centimeters thick is applied to the backside. Additionally, using wire mesh dimensions 25% larger than the initial slab damage yields the best performance. A comparative analysis of explosion-induced damage across different slab types indicates that reinforced concrete slabs with a 0.5-centimeter thick steel plate exhibit the largest damage area (8m2); whereas UHPC slabs show no damage, resulting in the smallest damage area. Further investigations into the dynamic response of these slabs demonstrate that advanced materials and reinforcement techniques significantly enhance their resilience against explosive forces. This study emphasizes the importance of innovative design strategies in civil engineering, highlighting that the adoption of UHPC slab minimizes structural damage and improves safety in high-risk environments. These findings underscore the necessity of incorporating modern materials and methodologies in protective structure design, ensuring better performance and longevity under extreme loading conditions. A comparative analysis of various methods for strengthening concrete slabs using identical materials shows that UHPC slabs outperform others in reducing deflection and failure. This illustrates their exceptional ability to withstand explosive dynamic loads. However, the primary limitation of UHPC slabs is their high cost and complexity of implementation. Reinforcement with steel sheets has proven more effective than wire mesh in minimizing deflection. In models reinforced with 0.5 cm steel sheets, deflection was reduced by 50% compared to conventional concrete slabs. The slabs reinforced with wire mesh demonstrated a significant decrease in failure rates compared to conventional slabs, with reductions ranging from 75% to 80% across various reinforcement methods using the same materials. Conversely, some models reinforced with steel sheets exhibited increased failure rates. The findings indicate that, in most cases, slabs with greater flexibility, such as those reinforced with wire mesh, sustained less damage. This can be attributed to the enhanced flexibility and ductility of wire mesh-reinforced slabs compared to those reinforced with steel sheets.

 
کلیدواژه‌های انگلیسی مقاله concrete slab,brittle failure,near field explosion,LS DYNA
نویسندگان مقاله سید احمد حسینی | seyyed ahmad Hosseini
Assistant Professor of Malik Ashtar University of Technology
استادیار دانشگاه صنعتی مالک اشتر

علیرضا گندم کار جوشقانی | Alireza Gandomkar Josheghani
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ترانه امین طاهری | Taraneh Amin Taheri
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نشانی اینترنتی http://mcej.modares.ac.ir/browse.php?a_code=A-10-10775-11&slc_lang=fa&sid=16
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