Ayda Şafak AĞAR ÖZBEK, Ronnie Refstrup PEDERSEN, Jaap WEERHEIJM

Boşluklu Betonun Darbe Yükü Altındaki Davranışının Mezoskopik Analizi

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

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.

Keywords:

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

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