Experimental Study on Fire Resistance Performance of Damaged Post-beam Mortise-Tenon JointS

In order to study the fire resistance performance of damaged post-beam mortise-tenon joints, three mortise-tenon joints without damage and three mortise-tenon joints with different damage forms were made. One joint was loaded at ambient temperature to obtain the ultimate bearing capacity, and the remaining five joints were subjected to ISO 834 standard fire conditions under 30% load level. The influence of damage on fire resistance performance of mortise-tenon joints were analysed. The bearing capacity test at ambient temperature shows that, when the load arrived 13.66 kN, the load–displacement curve dropped suddenly due to cracking at the tenon where the cross section varied. The fire resistance tests show that, the displacement of the beam end of the undamaged mortise-tenon joints increased suddenly at about 54 min, but the load still can be carried by the shallower part of the tenon after cracking at the tenon. Compared with the undamaged mortise-tenon joints, the displacement of beam end of joints with wood decay or crack at the tenon increased more quickly in fire. However, the influence of looseness was less obvious. In addition, as the displacement increased, gaps in the joints increased, and the influence of gap increase on heat transfer cannot be ignored.