Experimental study on fire resistance of traditional timber mortise-tenon joints with damages

Abstract

This paper presents the experimental results on the fire resistance of traditional timber mortise-tenon joints with looseness, decay and cracking in the jointing area. Static loading test and fire resistance tests were conducted on six full scale joint specimens. The development of the temperature, the charring depth and rate, and the degradation of the rotational stiffness of the joints with fire exposure time was quantified. It was found that the service damage can have significant influence on the fire resistance of the traditional timber mortise-tenon joints. The charring rate calculated from the beam and column cross-sections is close to the recommended value in design code for softwood. The displacement of the damaged joints with wood decay and cracking increased by 69% and 90%, respectively, with respect to that of the undamaged joint after 30 min of dire exposure. The rotational stiffness of a damaged joint after 30 min of fire exposure can drop down to 11.4% of the initial rotational stiffness of a sound joint at ambient temperature. The influence of the stiffness degradation of joints on the moment redistribution and fire endurance of neighbouring beams and columns is worth of further investigation.