Fire Response of Steel Column Trees with End-Plate Connections

Abstract

This paper presents the results of experimental research on the fire response of steel beams and their end-plate connections in column-tree moment-resisting frames (CMRFs). Using subframe assembly, full-scale steel beams with different stub-to-link end-plate connections were tested under a standard fire curve. The failure modes as well as the structural and thermal responses of the beam and the end-plate connections were studied. The influence of critical factors, including bolt grade and flange plate’s size, were investigated. The findings of the experimental studies indicate that the beam flexural failure occurs at the temperature of 720°C when deflections surpass the limiting value specified in a relevant British Standard Institution standard. The end-plate connections fail when the temperature exceeds 760°C, while the beam experiences deflections larger than span/20. The results also show that the plate bending, the bolt tensile fracture, and thread stripping control the failure of the end-plate connection in fire conditions. The end-plate connection detail has a considerable effect on the fire performance of the beam, e.g., using Grade 8.8 bolts and thicker plates in the end-plate connection can enhance the fire resistance and rating of the beams and their connections in steel CMRFs.