Seismic-induced fire resistance of composite welded beam-to-column joints with concrete-filled tubes

Major earthquakes in urban areas have often been followed by significant fires that cause extensive damage to property. Therefore, a seismic-induced fire is a scenario that should be addressed properly in performance-based engineering. In this paper, numerical and experimental results of welded steel–concrete composite full-strength beam-to-column joints under post-earthquake fires are described. This was part of a European project aimed at developing fundamental data and prequalification design guidelines of ductile and fire-resistant composite beam-to-column joints with concrete-filled tubes. In detail, seismic and fire analyses were used to design moment-resisting frames endowed with the proposed joint typology. A total of six specimens were designed and subjected to both monotonic and cyclic lateral loads. The specimens were subassemblages of beam-to-column joints, and performed well. Since the scope of the project was to promote joint typologies able to survive a seismic-induced fire, some specimens were pre-damaged before being subjected to fire loadings by imposing monotonic loads equivalent to damage levels induced by seismic loadings. Thus, after fire testing, valuable information about the performance of the proposed joint typology was obtained, and the adequacy of the concurrent seismic and fire design was demonstrated.

► Numerical and experimental results of welded steel–concrete composite beam-to-column joints under post-earthquake fires were described.
► Some specimens were pre-damaged, before being subjected to fire loadings, by imposing a damage level induced by seismic loadings.
► Fire experimental tests conducted on undamaged and seismic pre-damaged joints were presented.
► Experimental results showed that there was no noticeable difference in the fire performance between damaged and undamaged specimens.
► Fire tests demonstrated the ability of designed joints to survive a design seismic event of 0.4 g p.g.a. earthquake with a return period of 475 years.