Performance of steel beams with endplate connections exposed to fire

This paper presents results from an experimental study on the fire behavior of endplate joints and the connected steel beams in a moment resisting frame (MRF). Utilizing the subframe assemblage, full-scale steel beams with various endplate connections were tested according to the ISO834 standard fire exposure. The thermal and structural responses of the beam and its endplate joints to the column, together with failure modes were monitored throughout the fire test. The effect of key factors such as endplate dimensions, bolt size and grade, and the presence of stiffeners were investigated. The results of the fire tests show that the specimen experiences flexural failure in 746–773°C temperature range, through mid-span deflection exceeding the deflection limit as per British standard 476. When the beam experienced a deflection greater than span/20, the endplate joints got fractured at about 40 min in to fire at temperatures higher than 815°C. The results also indicated that the endplate bending and the tensile fracture of the bolts control the failure of the endplate joint under fire exposure. The endplate connection details have a notable influence on the beam’s behavior under fire conditions, and the use of grade 10.9 bolts and wider endplates in the connection can improve the fire resistance of MRFs.