Experiment Study on Fire Endurance of Mortise-tenon Joint in Timber Structures

Abstract

To learn the fire resistance performance of wood mortise-tenon joints of commonly used wooden species in China, 4 framed mortise-tenon joints commonly used in ancient wooden structures were exposed to fire, and 1 contrast specimen of bearing capacity test was experimentally studied. It is found that, in the capacity test, the vertical displacement of the contrast specimen in the middle of the beam changes linearly with the load. Meanwhile, there is no obvious yield point and the specimen has poor ductility. The value of the constant load of 4 specimen applied in the fire endurance test was identified according to the bearing capacity of the reference specimen and the different load ratio. The fire endurance of specimen with a load ratio of 25%, 37.5% and 50% was 59, 44, 21 minutes respectively, and the fire endurance of the specimen with fire proof coating and a load ratio of 50% was 58 minutes, which indicates that the decrease of load ratio and the fire proof coating can both effectively increase the fire endurance of mortise-tenon connection. Temperature data have shown that the load ratio has little impact on the rate of temperature rise, and the small gaps of 2~4 mm between the tenon and the mortise has little impact on the heat transfer of wood.

Keywords: mortise-tenon joint,  fire endurance,  section temperature,  load level,  failure mode