ANALYSIS ON THE FIRE RESISTANCE OF SQUARE CONCRETE-FILLED STEEL TUBULAR COLUMN TO COMPOSITE BEAM WITH OUTER RING PLATE CONNECTIONS AFTER EARTHQUAKE DAMAGE

To study the fire resistance of the square concrete-filled steel tubular column to composite beam with outer ring plate connections after earthquake damage, finite element numerical models were established and verified by experimental data of other researchers. The finite element models for the fire resistance of composite beam joints under three fire conditions after earthquakes were established. The impact of the shedding position and degree of the fire protection layer of the column in hysteretic loading and three fire conditions on the fire resistance and failure modes was analyzed. The results indicate that the stress value and deformation degree of the steel tube increased obviously with the increase of the damage degree of the joint under the hysteretic loading at the column end. When the joint was exposed to fire in the area below the RC slab, the temperature gradient of the stud from the bottom to the top was obvious with the increase of the fire time. The temperature field distribution of the RC slab was wavy due to the influence of the stud. Different damage degrees and different fire conditions had significant effects on the failure modes. However, there was no significant difference on the failure modes with or without the fire protection layer falling off under the three fire conditions. Under the two fire conditions in the area below the RC slab and the area above the RC slab, the shedding fire layer had a significant influence on the fire resistance of severely damaged joints. Under the condition that both the upper and lower areas of the RC slab were under fire, the shedding fire layer had no significant influence on the fire resistance of the joints.