Analysis of Strength Reduction Factor for Axially-Loaded Circular Columns with Fiber Reinforced Polymer

Abstract

The code and regulations use strength reduction factors to take into account the uncertainties of the random variables considered in structural design. In this study, for plain concrete columns and reinforced concrete columns (tie-reinforced column) wrapped with carbon fiber polymer (CFRP) under axial load obtained from literature, the strength reduction factors (ϕ) were calculated according to second-order moment approach by taking into account the target reliability index (β) and, different coefficient of variation of random variables of performance function [1]. In the calculations, the target reliability index was taken β=3.5 and the corresponding probability of failure as p_F=2.33〖*10〗^(-4). In ACI 318-19, the strength reduction factors for plain column and tie-reinforced column under axial load are 0.60 and 0.65, respectively. As a result of study, the strength reduction factors recommended in the ACI 318-19 for columns reinforced with fiber polymer were compared with the strength reduction factors obtained for different coefficient of variation.

Keywords

• Strength reduction factor
• target reliability
• fiber polymer
• second moment approach
• probabilistic design

Eksenel Yük Altındaki Lifli Polimer İle Sargılı Dairesel Enkesitli Kolonlarda Dayanım Azaltma Katsayısının İncelenmesi

Abstract

Yönetmeliklerde, yapısal tasarımda göz önüne alınan rasgele değişkenlerin belirsizliklerini hesaba katmak için dayanım azaltma katsayıları kullanılır. Bu amaçla, çalışma kapsamında literatürden elde edilen karbon lifli polimer (CFRP) ile sargılı, boyuna ve enine donatılı (dairesel etriye) ve donatısız eksenel yük etkisindeki kolon numuneleri için, hedef güvenilirlik indeksi (β) ve performans fonksiyonunu oluşturan rasgele değişkenlere ilişkin farklı varyasyon katsayıları göz önüne alınarak ikinci moment yaklaşımına göre dayanım azaltma katsayıları (ϕ) hesaplanmıştır [1]. Hesaplamalarda, β=3.5 ve buna karşılık gelen göçme olasılığı değeri p_F=2.33〖*10〗^(-4) olarak alınmıştır. ACI 318-19 yönetmeliğinde, eksenel yük etkisindeki donatısız kolonlar ve etriyeli kolonlar için dayanım azaltma katsayısının değerleri sırasıyla 0.60 ve 0.65 olarak önerilmiştir. Çalışma sonucunda lifli polimerle güçlendirilmiş kolonlar için ACI 318-19 yönetmeliğinde önerilen dayanım azaltma katsayısı değerleri, farklı varyasyon katsayıları için elde edilen dayanım azaltma katsayısı değerleri ile karşılaştırılmıştır.

Keywords

• Dayanım Azaltma Katsayısı
• Hedef güvenilirlik indeksi
• lifli polimer
• ikinci moment yaklaşımı
• olasılıksal tasarım

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