Betonarme elemanlarda donatı burkulmasının kafes kiriş analojisi ile sayısal modellenmesi

Year 2018, Volume: 24 Issue: 3, 384 - 389, 29.06.2018

Sadık Can Girgin

Abstract

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.

Keywords

Doğrusal olmayan kafes model, Donatı burkulması, Betonarme

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

Abstract

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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