Fire Resistance and Mechanical Properties of Wooden Dou-Gong Brackets in Chinese Traditional Architecture Exposed to Different Fire Load Levels

Dou-Gong brackets, the distinctive structural element in ancient Chinese architecture, fulfill critical roles in load transfer, span reduction, and decoration, making its preservation vital for safeguarding wooden heritage buildings. This study investigates the combustion performance and residual load-bearing capacity of key Dou-Gong bracket components—Zuo-dou, Zheng-xin-gua-gong, and Qiao—exposed to varying fire conditions. The results reveal that an increasing fire load elevates heating rates and peak temperatures of wood substrates, resulting in a significant degradation of structural integrity. At a fire load of 55 kW, the peak temperatures at the bottom, joint edge, and top of the Dou-Gong brackets reach 755.3 °C, 489.9 °C, and 620.7 °C, respectively, representing increases of 2%, 65%, and 38%, respectively, compared to those observed at a fire load of 20 kW. Moreover, the charring rate of Dou-Gong bracket increases from 0.22–0.26 mm/min at a fire load of 20 kW to 0.50–0.56 mm/min at a fire load of 55 kW, accompanied by an increase in mass loss rate from 28.5% to 36.9%. These findings highlight the significant impact of fire conditions on the fire characteristic and structural integrity of Dou-Gong brackets, providing the first quantitative evidence of their degradation under fire exposure. By addressing this vulnerability, the study contributes to the scientific preservation of ancient wooden architecture under contemporary fire risk scenarios.