طراحی بهینه‌ی پوشش تونل با بتن الیافی پلیمری بر مبنای ظرفیت جذب انرژی

نوع مقاله: مقاله پژوهشی

نویسنده

استادیار؛ دانشکده‌ی مهندسی آب و محیط زیست؛ دانشگاه صنعت آب و برق

چکیده

پتانسیل بالای جذب انرژی بتن‌های الیافی، این نوع مصالح را به عنوان گزینه‌ای مناسب برای انواع کاربری‌ها مطرح نموده است. این کاربرد به ویژه در محیط‌های تحت تغییر شکل و جابجایی‌های قابل توجه مانند انواع سازه‌های زیرزمینی اهمیت بیش‌تری دارد. با تامین ظرفیت جذب انرژی بالاتر، انعطاف‌پذیری سازه‌ی نگهدارنده افزایش و ضخامت و میزان مصالح مورد نیاز برای پوشش کاهش می‌یابد و سازه‌ی اقتصادی‌تری بدست می‌آید. برای افزایش ظرفیت جذب انرژی در ترکیبات مسلح به الیاف، در حالت عادی به محتوای الیاف بیش‌تری نیاز است. این امر، استفاده از این مصالح را با محدودیت‌های اقتصادی مواجه نموده است. این مقاله به معرفی یک پوشش بتنی مسلح به الیاف پلیمری بهینه می‌پردازد که حداقل محتوای الیاف ممکن و حداکثر ظرفیت جذب انرژی را دارد. نتایج این پژوهش حاصل مجموعه‌ای نسبتاً جامع از آزمایش‌ها با انواع مختلف افزودنی‌ها و محتوای الیاف است و پیشنهاداتی را برای دستیابی به یک طراحی بهینه بر مبنای نتایج تجربی ارایه داده است. بدین منظور از آزمایش‌های استاندارد تیر و پانل برای تعیین ظرفیت جذب انرژی و سایر خصوصیات مورد نیاز طراحی استفاده شده است. در نهایت با استفاده از نتایج طرح‌های اختلاط بهینه، نمودار پیشنهادی طراحی پوشش‌های تونل بر مبنای ظرفیت جذب انرژی ارایه شده است.

کلیدواژه‌ها


عنوان مقاله [English]

Energy-Based Optimized Design of Polymer Fiber-Reinforced Tunnel Lining

نویسنده [English]

  • Mohammad Safi
Assistant Professor; Faculty of Water and Environmental Eng.; Power and Water University of Technology
چکیده [English]

This research aims to introduce an optimized design with minimum possible fiber content while having the maximum possible energy absorption capacity. A series of laboratory tests were conducted with various additive and fiber contents to reach this goal. General recommendations for achieving the optimized results were proposed based on the experimental results. Beam and panel tests were used to account for energy absorption capacity.
 
Introduction
Due to the relevance of the energy absorption capacity of fibrous concrete, several entities have been proposed for evaluating this property that include the toughness indices, the equivalent flexural strength and the fracture energy. Among these entities, the fracture energy is the most used in the constitutive models for characterizing the concrete tensile post-cracking behavior. The other entities have not been widely used in numerical simulation of the behavior of Fiber-Reinforced Concrete (FRC) structures. The generic mechanical response contains a linear regime, in which very little permanent micro-structural changes and deformation take place, and a nonlinear regime, in which permanent micro-structural changes occur in a stable manner.
 
Methodology and Approaches
In order to obtain the most appropriate mix characteristics with the highest energy absorption, an experimental study using 33 beam and rectangular panels was performed by the author. Tests were conducted for various fiber contents and the maximum specific absorbed energy was measured. The small amount of energy absorbed by plain concrete panel was ignored.
 
Results and Conclusions
The experimental study performed for finding optimized mix design of fiber reinforced concrete showed that applying some changes to the mix design, we can reduce the amount of fiber while keeping the energy absorption capacity constant. This totally results in a high performance of self-compacting fiber reinforced concrete with rather high strength and high energy absorption capacity. Such composite shows high resistance and ductility and can be excellent for both normal and special structural applications. Higher energy absorption levels may also be obtained by following a similar procedure as was performed in this study. Note that, although more fibers result in more energy absorption up to a certain level, the failure mechanism and structural behavior do not change, and thus, the same objectives can be met by using minimum amounts of fibers.

کلیدواژه‌ها [English]

  • Tunnel Lining
  • Energy absorption
  • Fiber Reinforced Composite
  • Panel Test
  • Mix Design
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[7]     Grimstad, E. & Barton, N. (1993). Updating the Q-system for NMT. In Kompen, Opsahl, and Berg (Ed.), Proceedings of the International Symposium on Sprayed Concrete-Modern Use of Wet Mix Sprayed Concrete for Underground Support (pp. 163-177 & 234-241). Oslo, Norway: Norwegian Concrete Association.

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