شبیه‌سازی عددی انبساط غیرهمسانگرد ناشی از واکنش قلیایی سنگدانه‌ها در اعضای بتنی

نوع مقاله : پژوهشی اصیل (کامل)

نویسندگان
امیررضا تیموری
حسین یوسف پور
بهرام نوائی نیا
دانشگاه صنعتی نوشیروانی بابل
10.22034/22.4.5
چکیده
واکنش قلیایی سنگدانه‌ها نوعی فرایند شیمیایی مخرب و وابسته به زمان است که بین ­یون­ های قلیایی موجود در سیمان و مواد معدنی موجود در انواع مشخصی از سنگدانه­ ها که دارای سیلیس واکنش‌پذیر یا کربنات می‌باشند رخ می­ دهد. این واکنش سبب ایجاد نوعی ژل در بتن می­ گردد که تمایل به جذب آب داشته و در صورت جذب رطوبت از محیط اطراف بصورت غیریکنواخت منبسط می‌شود. این انبساط غیریکنواخت سبب وقوع تنش‌های کششی بزرگتر از مقاومت کششی بتن و در نتیجه ترک‌خوردگی آن می‌شود. با وقوع چنین ترک‌هایی، بسیاری از پارامترهای رفتار مکانیکی بتن نظیر مقاومت فشاری، مقاومت کششی و مدول الاستیسیته تغییر کرده و در نتیجه­ی آن­، پایداری و قابلیت سرویس‌دهی سازه به طور جدی تحت تاثیر قرار می­گیرند. برای شبیه­سازی رفتار سازه­ها در برابر این واکنش­ها، یکی از مهمترین محاسبات، توزیع جهتی صحیح انبساط حجمی ناشی از این واکنش­ ها می­ باشد، که بر پیش­ بینی تنش­ ها و کرنش ­های موجود در سازه اثر قابل توجهی دارد. در پژوهش حاضر، با استفاده از قابلیت سابروتین­ نویسی در نرم افزار اجزای محدود آباکوس، یک مدل ریاضی برای شبیه‌سازی انبساط مرتبط با واکنش­ های قلیایی سنگدانه ­ها و خسارت ناشی از آن در المان‌ها و اعضای بتن مسلح توسعه داده شد. مدل مورد اشاره با توجه به وضعیت تنش در بتن در هر گام زمانی تحلیل، کرنش آزاد حجمی را بصورت غیرهمسانگرد در بتن توزیع می‌کند. به‌منظور صحت‌سنجی مدل توسعه داده شده، نتایج حاصل از آن تحت شرایط مختلف آرماتورگذاری و بارگذاری با توجه به نتایج آزمایشگاهی مورد سنجش قرار گرفت. مقایسه با نتایج آزمایشگاهی نشان می‌دهد که مدل عددی توسعه داده شده قادر است با دقت مناسب توزیع جهتی انبساط غیرهمسانگرد ناشی از واکنش قلیایی سنگدانه‌ها را در بتن مسلح و غیرمسلح شبیه‌سازی کند. نتایج حاصل از مدل اجزای محدود همچنین حاکی از آن است که اصلاح مشخصات مکانیکی بتن طی شبیه‌سازی، تاثیر اندکی بر توزیع جهتی انبساط دارد. بعلاوه مشاهده شد که مدل مورد استفاده تسلیم آرماتورها را در انبساط کلی متناظر با کرنش تسلیم فولاد (حدود 2/0 درصد) نشان می­دهد که پیرو آن تغییرات تنش الگوی متفاوتی را دنبال می­ نماید. چارچوب عددی معرفی شده در این مقاله می­تواند به نحو موثری در مدل­سازی سازه ­های تحت اثر واکنش­های قلیایی سنگدانه­ ها مورد استفاده قرار گرفته و به منظور تعیین تنش­ ها و خسارات ناشی از پیشرفت این واکنش استفاده شود.

کلیدواژه‌ها

موضوعات

عنوان مقاله English

Numerical Framework for Simulation of Anisotropic Expansion due to Alkali-Aggregate Reactions in Concrete Members

نویسندگان English

Amir Reza Teymouri
Hossein Yousefpour
Bahram Navayi Neya
Babol Noshirvani University of Technology
چکیده English

Alkali-Aggregate Reaction (AAR) is a type of destructive and time-dependent chemical process in concrete that occurs between alkali ions in the cement and reactive minerals in certain types of aggregates. First recognized in 1930s, AAR is divided into two major categories of Alkali-Silica Reaction (ASR) and Alkali-Carbonate Reaction (ACR), both of which produce an expansive gel in the concrete which expands as a result of water absorption. The expansion of the AAR gel exerts significant internal pressure in the concrete, which may lead to internal and external cracks. With the occurrence of such cracks, many parameters affecting the stiffness and strength of the structure, such as compressive strength, tensile strength, and modulus of elasticity are diminished. As a result, the safety and serviceability of the structure may be seriously impacted. While advances in concrete materials science have led to means to prevent AAR in new construction, numerous existing structures worldwide, such as dams, power plants, and bridges, are affected by these reactions, the replacement of which may be impractical, or in some cases, impossible. As a result, it is crucial to simulate the behavior of such structures for reliable estimation of their safety and providing rehabilitation measures as necessary. One of the major indicators of AAR is the anisotropic expansion it generates inside the concrete member, which changes drastically based on the boundary conditions and internal and external restraint imposed on the expansions. As a result, the prediction of the anisotropic expansions is of utmost importance in successful simulation of AAR-affected reinforced concrete structures. This paper presents a practical simulation methodology for estimating the directional distribution of AAR expansions. The methodology makes use of the user subroutine capability in the finite element software Abaqus. A mathematical model is used to simulation AAR-related expansion based on the stress tensor, whereas concrete damage is simulated using the concrete damage plasticity model. The model is used to simulate a variety of AAR-affected reinforced and plain concrete cube and beam specimens for which the directional expansion data have been reported in the literature. Comparison between numerical and experimental results shows that the proposed methodology is capable of reliably simulating the AAR-induced expansions and the interaction between AAR expansions and the ensuing damage for a variety of reinforcement configurations. The model showed that the yield strength of reinforcing bars plays a major role in the directional distribution of expansion. However, changes in the mechanical properties of concrete were found to be inconsequential in the distribution of the expansions. Moreover, changes in distance between reinforcing bars and the reinforcement ratio in each direction were observed to affect the accuracy of the model. However, the model was found to be successful in reasonably capturing the trends in all case studies investigated. The results of this study are of great value to the simulation of AAR-affected reinforced concrete structures.

کلیدواژه‌ها English

Alkali-Aggregate Reaction
Expansion
reinforced concrete
finite element method
Stanton, T. E., 1940. Expansion of Concrete through Reaction between Cement and Aggregate. Transactions of the American Society of Civil Engineers, 101(1), pp. 54-84.
Fournier, B. and Berube, M.A., 2000. Alkali-Aggregate Reaction in Concrete: A Review of Basic Concepts and Engineering Implications. Canadian Journal of Civil Engineering, 27(2), pp. 167-191.
Deschenes, D.J., Bayrak, O. and Folliard K.J., 2009. ASR/DEF-Damaged Bent Caps: Shear Tests and Field Implications. Master's thesis, The University of Texas at Austin, Austin, Texas, United States, 277 pp.
Berube, M.A. and Fournier, B., 1993. Canadian Experience with Testing for Alkali-Aggregate Reactivity in Concrete. Cement & Concrete Composite, 15(1-2), pp. 27-47.
Thomas, M.D.A., Fournier, B. and Folliard, K.J., 2013. Alkali Aggregate Reactivity (AAR) Facts Book (No. FHWA-HIF-13-019). United States, Federal Highway Administration, Office of Pavement Technology.
Rigden, S.R., Majlesi, Y. and Burley, E., 1995. Investigation of Factors Influencing the Expansive Behavior, Compressive Strength and Modulus of Rupture of Alkali-Silica Reactive Concrete using Laboratory Concrete Mixes. Magazine of Concrete Research, 47(170), pp. 11-21.
Ng, K.E. and Clark, L.A., 1992. Punching Tests on Slabs with Alkali-Silica Reaction. The Structural Engineer, 70(14), pp. 245-252.
Folliard, K.J., Barborak, R., Drimalas, T., Du, L., Garber, S., Ideker, J., Ley, T., Williams, S., Juenger, M., Fournier, B. and Thomas M.D.A., 2006. Preventing ASR/DEF in New Concrete: Final Report. Technical Report No. FHWA/TX-06/0-4085-5, Center of Transportation Research, The University of Texas at Austin, Austin, TX, 266 pp.
Thomas, M.D.A., Fournier, B. and Folliard, K.J., 2008. Report on Determining the Reactivity Concrete Aggregates and Selecting Appropriate Measures for Preventing Deleterious Expansion in New Concrete Construction. Technical Report No. FHWA-HIF-09-001, The Transtec Group, Inc., Austin, TX, 28 pp.
Thomas, M., Dunster, A., Nixon, P. and Blackwell, B., 2011. Effect of Fly Ash on the Expansion of Concrete due to Alkali-Silica Reaction-Exposure Site Studies. Cement & Concrete Composites, 33(3), pp. 359-367.
Leemann, A., Bernard, L., Alahrache, S. and Winnefeld, F., 2015. ASR Prevention - Effect of Aluminum and Lithium Ions on the Reaction Products. Cement and Concrete Research, 76, pp. 192-201.
Shi, Z., Shi, C., Zhang, J., Wan, S., Zhang, Z. and Ou, Z., 2018. Alkali-Silica Reaction in Waterglass-Activated Slag Mortars Incorporating Fly Ash and Metakaolin. Cement and Concrete Research. 108, pp. 10-19.
Swamy, R.N. and Al-Asali, M.M., 1988. Engineering Properties of Concrete Affected by Alkali-Silica Reaction. ACI Materials Journal, 85(5), pp. 367-374.
Ahmed, T., Burley, E., Rigden, S. and Abu-Tair, A.I., 2003. The Effect of Alkali Reactivity on the Mechanical Properties of Concrete. Construction and Building Materials, 17(2), pp. 123-144.
Smaoui, N., Bissonnette, B., Berube, M.A., Fournier, B. and Durand, B., 2006. Mechanical Properties of ASR-Affected Concrete Containing Fine or Coarse Reactive Aggregates. Journal of ASTM International, 3(3), pp. 1-16.
Giannini, E.R. and Folliard, K.J., 2012. Stiffness Damage and Mechanical Testing of Core Specimens for the Evaluation of Structures Affected by ASR. In Proceedings of the 14th International Conference on Alkali-Aggregate Reaction in Concrete.
American Concrete Institute, 1998. ACI 221.1R-98: Report on Alkali-Aggregate Reactivity. Farmington Hills, MI: ACI.
The Institution of Structural Engineers, 1992. Structural Effects of Alkali-Silica Reaction: Technical Guidance on the Appraisal of Existing Structures. London: SETO Ltd.
Wald, D.M., Allford, M.T., Bayrak, O. and Hrynyk, T.D., 2017. Development and Multiaxial Distribution of Expansions in Reinforced Concrete Elements Affected by Alkali-Silica Reaction. Structural Concrete, 18(6), pp. 914-928.
Allford, M.T., Bayrak, O. and Hrynyk, T.D., 2016. Expansion Behavior of Reinforced Concrete Elements Due to Alkali-Silica Reaction. Master's thesis, The University of Texas at Austin, Austin, Texas, United States, 144 pp.
Wald, D.M., Martinez, G.A. and Bayrak, O., 2017. Expansion Behavior of a Biaxially Reinforced Concrete Member Affected by Alkali-Silica Reaction. Structural Concrete, 18(4), pp. 1-11.
Wald, D.M., Bayrak, O. and Hrynyk T.D., 2017. ASR Expansion Behavior in Reinforced Concrete-Experimentation and Numerical Modeling for Practical Application. Ph.D. dissertation, The University of Taxes at Austin, Austin, Texas, United States, 281 pp.
Bracci, J.M., Gardoni, P., Olave, M.K.E. and Trejo, D., 2012. Performance of Lap Splices in Large-Scale Column Specimens Affected by ASR and/or DEF. Technical Report No. FHWA/TX-12/0-5722-1, Texas Transportation Institute, The Texas A&M University System, College Station, TX, 380 pp.
Olave, M.K.E., Bracci, J.M., Gardoni, P. and Trejo, D., 2015. Performance of RC Columns Affected by ASR. I: Accelerated Exposure and Damage. Journal of Bridge Engineering, 20(3), pp. 1-11.
Gautam, B.P., Panesar, D.K., Sheikh, S.A. and Vecchio, F.J., 2017. Multiaxial Expansion-Stress Relationship for Alkali Silica Reaction-Affected Concrete. ACI Materials Journal, 114(1), pp. 171-184.
Lamea, M. and Mirzabozorg, H., 2015. Modeling of Alkali-Aggregate Reaction Effects on Seismic Behavior of Concrete Arch Dams. Ph.D. thesis, K.N.Toosi University of Technology, Tehran, Iran, 203 pp. (In Persian)
Lamea, M. and Mirzabozorg, H., 2016. Alkali Aggregate Reaction Effects on an Arch Dam Behavior Including Simulation of Construction Stages and Contraction Joints. Structural Engineering International, 26(1), pp. 37-44.
Gorga, R.V., Sanchez, L.F.M. and Martin-Perez, B., 2018. FE Approach to Perform the Condition Assessment of a Concrete Overpass Damaged by ASR After 50 Years in Service. Engineering Structures, 177, pp. 133-146.
Pourbehi, M.S., Zijl, G.P.A.G.V. and Strasheim, J.A.V.B., 2019. Analysis of Combined Action of Seismic Loads and Alkali-Silica Reaction in Concrete Dams Considering the Key Chemical-Physical-Mechanical Factors and Fluid-Structure Interaction. Engineering Structures, 195, pp. 263-273.
Abaqus 6.14 (Software), 2014. Dassault Systemes Simulia Corporation, Providence, RI.
Larive, C. and Coussy, M.O., 1997. Combined Contribution of Experiments and Modelling to the Understanding of Alkali-Aggregate Reaction and its Mechanical Consequences. Ph.D. thesis, National Institute of Bridges and Roads, Paris, France, 327 pp. (In French)
Ulm, F.J., Coussy, O., Kefei, L. and Larive, C., 2000. Thermo-Chemo-Mechanics of ASR Expansion in Concrete Structures. Journal of Engineering Mechanics, 126(3), pp. 233-242.
MATLAB 7.10.0 (R2012a), 2013. The MathWorks Inc., Natick, Massachusetts, United States.
Wight, J.K., 2015. Reinforced Concrete: Mechanics and Design (Seventh Edition). Hoboken, New Jersey: Pearson.
Belarbi, A. and Hsu, T.T.C., 1994. Constitutive Laws of Concrete in Tension and Reinforcing Bars Stiffened by Concrete. ACI Structural Journal, 91(4), pp. 465-474.
مهندسی عمران مدرس
دوره 22، شماره 4
خرداد و تیر 1401
صفحه 61-78