Boşluklu Betonun Darbe Yükü Altındaki Davranışının Mezoskopik Analizi

Öz

Boşluklu beton, yüksek miktarda mezo-boyutta hava boşluğu içeren özel bir tip betondur. İçerdiği boşluklar nedeniyle boşluklu betonun mekanik özellikleri normal betonlardan oldukça farklıdır. Bu nümerik çalışmanın amacı, boşluklu betonun dinamik yük altındaki davranışının mezoskopik olarak analiz edilmesidir. Gerçekleştirilen sonlu eleman analizlerinde, açık direkt entegrasyon (explicit direct integration) yöntemi kullanılmıştır. Betonun çimento bazlı fazlarının tanımlanmasında Beton Hasar Plastisite Modeli kullanılmıştır. Boşluklu betonun dört fazlı bir malzeme olarak gerçeğe yakın bir şekilde temsil edilebilmesi için her bir fazın ayrı bir şekilde tanımlanabildiği bir sonlu eleman ağı geliştirme programı oluşturulmuştur. Boşlukların etkilerinin daha iyi araştırılabilmesi için dairesel boşluklar içeren yalın betonlar şeklinde tanımlanmış model boşluklu betonlar ayrıca incelenmiştir. Gerçek boşluklu betonların nümerik incelemeleri ile elde edilen sonuçlar, gerek darbe dayanımı gerekse çatlak dağılımı yönünden deneysel sonuçlarla uyum göstermektedir.

Anahtar Kelimeler

• Açık zaman hesabı,mezoskopik analiz,boşluklu beton,beton hasar plastisite modeli

Mesoscopic Analysis of the Behavior of Porous Concrete under Impact Loading

Öz

Porous concrete is a special type of cementitious material incorporating a high amount of meso-sized air pores that makes its mechanical characteristics markedly different from normal concrete. The objective of this numerical study is mesoscopically analyzing the behavior of porous concrete under dynamic loading. In the finite element analyses, explicit direct integration method was adopted. Concrete Damage Plasticity Model was selected to define the material properties of the cementitious phases. With the aim of realistically representing porous concrete as a four-phase material, a mesh generation program was developed where each phase was separately defined. In order to better investigate the effects of the properties of pores, model porous concretes were also analyzed in the form of plain concrete meshes incorporating circular pores. The numerical analysis results of real concrete mixtures were in good agreement with the experimental results both in terms of quantifying the impact strength as well as demonstrating a realistic crack pattern formation for the porous concretes that have been analyzed. 

Anahtar Kelimeler

• Explicit time integration,mesoscopical analysis,porous concrete,concrete damaged plasticity

Kaynakça

1. Yang J and Jiang G., Experimental study on properties of pervious concrete, Cement and Concrete Research, 33 (3), 381-386, 2003.
2. Marolf A, Neithalath N, Sell E, Wegner K, Weiss J, Olek J., Influence of aggregate size and gradation on the acoustic absorption of enhanced porosity concrete, ACI Materials Journal, 101(1), 82-91, 2004.
3. Lubliner, J.J., Oliver, S.O. and Oñate, E., A plastic-damage model for concrete, International Journal of Solids and Structures, 25(3), 229-326, 1989.
4. Lee, J. and Fenves, G.L., A plastic damage model for cyclic loading of concrete structures, Journal of Engineering Mechanics, ASCE, 124, 892–900, 1998.
5. Chaudhari S.V. and Chakrabarti, M.A., Modeling of concrete for nonlinear analysis using finite element code ABAQUS, International Journal of Computer Applications, 44(7), 14-18, 2012.
6. Jankowiak, T. and Lodygowski, T., Identification of parameters of concrete damage plasticity constitutive model, Foundations of Civil and Environmental Engineering, 6, 53-69, 2005.
7. ABAQUS Analysis User’s Manual, Simulia, 2013.
8. Kmiecik, P. and Kaminski M., Modelling of reinforced concrete structures and composite structures with concrete strength degradation taken into consideration, Archives of Civil & Mechanical Engineering, 11(3), 623-636, 2011.

9. Timoshenko, S and Goodier, J.N., Theory of Elasticity, Prentice-Hall, 2001.
10. Green, D.J., An Introduction to the Mechanical Properties of Ceramics, Cambridge University Press, 1998
11. Agar Ozbek A.S., Weerheijm J., Schlangen E., van Breugel K., Investigating porous concrete with improved strength: Testing at different scales, Construction and Building Materials 41, 480-490, 2013.
12. Noh G. and Bathe K. J., An explicit time integration scheme for the analysis of wave propagations, Computers and Structures, 129, 178-193, 2013.
13. Farooq, U. and Gregory K., Explicit dynamic simulation of drop-weight low velocity impact on carbon fibrous composite panels, ARPN Journal of Engineering and Applied Sciences, 5(3), 50-61, 2010.
14. Huang, C.C. and Wu, T.Y., A Study on Dynamic Impact of Vertical Concrete Cask Tip-over Using Explicit Finite Element Analysis Procedures, Annals of Nuclear Energy 36(2), , 213–221, 2009.
15. Elmer,W. VII, Taciroglu, E. and McMichael, L., Dynamic Strength Increase of Plain Concrete From High Strain Rate Plasticity with Shear Dilation, International Journal of Impact Engineering, 45, 1–15, 2012.
16. Chopra, A.K., Dynamics of Structures: Theory and Applications to Earthquake Engineering, Prentice Hall, 2000.
17. Huebner, K.H., Dewhirst, D.L., Smith, D.H. and Byrom T.G., The Finite Element Method for Engineers, Wiley, 2001
18. Chen, Z., Shin, M. and Adrawes, B., Numerical simulation and parametric study of prestressed concrete crosstie and fastening system, PCI/NBC, September 29- October 2, Nashville, USA, 2012.
19. Sun, J. S., Lee, K. H. and Lee, P. H., Comparison of implicit and explicit finite element methods for dynamic problems, Journal of Materials Processing Technology, 105(1-2), 110-118, 2000.
20. Noels, L., Stainier, L. and Ponthot, J.P., Combined implicit/explicit time-integration algorithms for the numerical simulation of sheet metal forming, Journal of Computational and Applied Mathematics, 168(1-2), 331–339, 2004.
21. Dhanasekar, M. and Haider, W., Explicit finite element analysis of lightly reinforced masonry shear walls, Computers and Structures, 86(1-2), 15–26, 2008.
22. Siad L., Ouali M. O. and Benabbes A., Comparison of explicit and implicit finite element simulations of void growth and coalescence in porous ductile materials, Materials and Design, 29(2), 319–329, 2008.
23. Agar Ozbek A.S., Weerheijm J., Schlangen E., van Breugel K., Drop weight impact strength measurement method for porous concrete using laser Doppler velocimetry, Journal of Materials in Civil Engineering, 24(10), 1328-1336, 2012.
24. Deutsches Institut für Normung, Falsework calculation, design and construction DIN 4421:1982, Beuth Veriag GmbH, Berlin, Almanya, 1982
25. British Standards Institution, Falsework performance requirements and general design, Draft prEN 12812, Londra İngiltere, 1997.
26. Gorst, N.J.S., Williamson, S.J., Pallett, P.F. and Clark, L.A., Friction in temporary works, Research Report, University of Birmingham, U.K, 2003.