Betonarme elemanlarda donatı burkulmasının kafes kiriş analojisi ile sayısal modellenmesi

Deprem kuşağında yer alan bölgelerdeki betonarme yapılar, sismik performans hedeflerini sağlamak üzere tasarlanır. Betonarme elemanların uç bölgelerinde, boyuna donatılarda burkulmaya bağlı yanal şekil değiştirmeler gelişebilir. Betonarme yapıların performansa dayalı değerlendirilmesi doğrusal olmayan davranış üzerinde donatı burkulma etkilerini hesaba katan analitik modellere dayalı olmalıdır. Bu çalışmada, literatürde yer alan doğrusal olmayan kafes modelleme yaklaşımı donatı burkulmasından etkilenen betonarme elemanlar için genişletilmiştir. Doğrusal olmayan kafes kiriş modeli basınç etkisi altında diyagonal elemanlarda çift eksenli etkileri, yatay ve düşey beton elemanlarda ise çekme güçlenmesini dikkate almaktadır. Donatıları temsil eden kafes elemanlar, elastik olmayan burkulma ve kopmayı açık şekilde hesaba katan tek eksenli bir malzeme modeli ile tanımlanmıştır. Sunulan çalışmada, modelleme yaklaşımı bir betonarme kiriş testi sonuçları ile doğrulanmış ve sonlu eleman boyut değişiminin modeldeki etkileri araştırılmıştır. Sayısal model moment-ötelenme oranı ilişkisindeki dayanım azalmasını deney sonuçlarıyla uyumlu olarak hesaplamıştır.

Anahtar Kelimeler:

Doğrusal olmayan kafes model, Donatı burkulması, Betonarme

Numerical modeling of rebar buckling in reinforced concrete members using truss analogy

Reinforced concrete (RC) structures in earthquake prone regions are designed to achieve the seismic performance objectives. In end regions of RC members, longitudinal reinforcing bars may develop buckling due to high compressive strains under reversed cyclic loadings. The performance based assessment for RC structures should rely on analytical models which can account for the effect of rebar buckling on the nonlinear response. This study extends a previously proposed nonlinear truss modeling approach for modeling RC elements whose response is affected by rebar buckling. Nonlinear truss model includes diagonal truss elements accounting for biaxial effects in compression and tension stiffening for concrete elements in the horizontal and vertical directions. The truss elements representing reinforcing steel are provided with a uniaxial material model which can explicitly account for inelastic buckling and fracture of rebars. The modeling approach is validated with experimental test results on one RC beam considering mesh size effects on the response. Numerical model computed strength degradation in moment-drift ratio response of the beam in accordance with the experimental results.

Keywords:

Nonlinear truss model, Rebar buckling, Reinforced concrete,

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