Post-fire Behaviour of Axially Loaded Steel Pipe and Box T-joints

Abstract

This study aims to investigate the post-fire behavior of truss system T-joints made of pipe or box profiles under axial load using the finite element method. Hence, T-joints with different geometrical properties were modeled using the finite element program. First of all, heat transfer analysis was performed and the numerical models were heated based on the ISO 834 fire curve and then the joints were cooled. An axial load was applied from the end of the brace member to the joints, which were exposed to residual stresses and deformations after the fire, until they reached the maximum capacity. Each joint was failed due to plastification on the wall of the chord member. The strengths of the joints before and after the fire were compared. According to the findings obtained from the numerical results, the strength of tubular T-joints after fire decreases to up to 23.5%. In addition, the temperature distributions on the joints vary depending on the brace-to-chord member ratios and chord wall thicknesses. Residual stress and deformations after fire have a significant effect on the strength of both pipe and box T-joints.

Keywords

• Elevated Temperature
• Finite Element
• Fire
• Residual Stress
• Tubular Sections
• Truss

Eksenel Yüke Maruz Çelik Boru ve Kutu T-birleşimlerinin Yangın sonrası Davranışı

Abstract

Bu çalışma, boru ve kutu profillerden oluşmuş kafes sistem T-birleşimlerinin eksenel yük altında yangın sonrası davranışlarını sonlu elemanlar yöntemi kullanarak incelemeyi amaçlamaktadır. Bunu için farklı geometrik özelliklere sahip T-birleşimler sonlu elemanlar programı kullanılarak modellenildi. Öncelikle ısı transfer analizi yapılarak, oluşturulan sayısal modeller ISO 834 yangın eğrisine bağlı olarak ısıtıldı ve sonra soğutuldu. Yangın sonrası artık gerilmelere ve deformasyonlara maruz kalmış birleşimlere, maksimum dayanıma ulaşıncaya kadar örgü elemanı ucundan eksenel yük uygulanıldı. Tüm birleşimlerde göçme sınır durumu başlık elemanı cidarında plastikleşme olarak tespit edildi. Yangın öncesi ve sonrası birleşimlerin dayanımları karşılaştırıldı. Sayısal sonuçlardan elde edilinen bilgilere göre yangın sonrası tübüler T-birleşimlerin dayanımları %23,5 ’a kadar düşmektedir. Ayrıca, birleşimler üzerindeki sıcaklık dağılımları, örgü-başlık eleman oranlarına ve başlık elemanının et kalınlıklarına bağlı olarak değişmektedir. Yangın sonrasında oluşan artık gerilme ve deformasyonlar boru ve kutu T-birleşimlerin dayanımlarına önemli derecede etki etmektedir.

Keywords

• Artık Gerilme
• Kafes sistem
• Sonlu elemanlar
• Tübüler profil
• Yangın
• Yüksek sıcaklık
• Elevated Temperature
• Finite Element
• Fire
• Residual Stress
• Tubular Sections
• Truss

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