Experimental Study of Fire Resistance of Mortise–Tenon-Jointed Post–Beam Timber Frames with Intumescent Coatings

To investigate the fire resistance of mortise–tenon-jointed post–beam timber frames with intumescent coatings, standard fire tests were conducted on one uncoated frame and two frames with different coating quantities. The results showed that the intumescent coatings reduced the charring rates and effectively improved the fire endurance of the timber frames. Compared with the uncoated frame, the charring rates of the coated frames decreased by 9.4% and 11.3%, respectively, and their fire endurance increased by 83.1% and 99.4%, respectively. However, increasing the coating quantity had a limited effect on further improving the fire endurance of the frames. The fire endurance of a frame with a coating amount of 1,000 g/m2 increased by only 8.8% compared with that of a frame with a coating amount of 500 g/m2. Moreover, the coatings may alter the failure mode of the frames under fire conditions: the uncoated frame experienced bending failure of its beam, whereas the coated frames exhibited joint failure. A simplied method for prediction of the fire endurance of coated timber frames was proposed and showed good agreement with test results in this study and in literature.