木结构榫卯节点耐火极限试验研究

为研究我国古建木结构榫卯节点的抗火性能,进行了4个燕尾榫榫卯节点的耐火极限试验、以及1个未受火对比试件的承载力试验研究.承载力试验表明,未受火对比试件的梁跨中竖向位移基本随荷载线性变化,没有明显屈服点,延性较差.根据该对比试件的承载力试验值、以及各耐火极限试件持荷比参数取值,确定了耐火极限试件的预加恒定荷载值.耐火极限试验中,持荷比25%,37.5%,50%试件的耐火极限分别为59,44,21min,持荷比50%并涂有防火涂料试件的耐火极限为58min,表明持荷比的减小、以及采用防火涂料均可显著提高耐火极限.温度数据表明,持荷比对温度上升速率没有明显的影响,榫头与卯口之间2~4mm的微小间隙对传热的影响几乎可以忽略.

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

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.