Seismic fragility analysis of steel intermediate moment frames with column-tree connections

• Published in: Journal of Building Engineering 2021-12, Vol.44, p.102955, Article 102955
• Main Authors: Yu, Eunjong, Kim, Taewan, Park, Ji-Hun
• Format: Article
• Language: English
• Subjects: Beam splice slip; Collapse probability; Column-tree connection; Seismic fragility; Steel intermediate moment frame
• ISSN: 2352-7102; 2352-7102
• DOI: 10.1016/j.jobe.2021.102955

Steel intermediate moment frames (SIMFs) with column-tree connections have an advantage in that they can ensure quality control and decrease construction cost and time by the factory welding of stub beams to columns and field bolting at the beam splice. Furthermore, the amount of steel can be reduced by distributing the seismic lateral load to the entire frame, for which beam-to-column joints are fully restrained. Despite such merits, concerns about slip at the beam splice and concentrated deformation in the weak panel zone also exist. Therefore, the influence of beam splice slip and weak panel zone deformation on the seismic performance of the SIMF with column-tree connections was examined numerically by seismic fragility assessment. For comparison, the seismic fragility of a SIMF with conventional field-welded connections was also examined. The result showed that the beams and panel zones share energy absorption in the SIMF with column-tree connections, even though the panel zones are weaker than the beams, because the beam splice slip can reduce the concentration of deformation on the weak panel zone. The collapse probability of a SIMF with column-tree connections is expected to be reduced to a value as low as a SIMF with conventional connections if the quality of test data and modeling are improved. •Column-tree connection is a good choice for beam-to-column joints of SIMFs.•Beam splice slip reduces deformation concentration on weak panel zone.•Beams and panel zones in SIMF with column-tree connections share energy absorption.•Column-tree connections may have fragility equivalent to conventional ones.