Fire characteristic evolution and residual bearing capacity analysis of Chinese wooden Dou-Gong brackets under different natural service times
摘要
As one of the most unique structures in wooden heritage buildings, the Dou-gong is of great structural importance and cultural value. For investigating the fire resistance of the ancient wooden Dou-gong brackets, the fire characteristics and residual bearing capacity of the main stress brackets of the Dou-gong (Zuo-dou, Zheng-xin-gua-gong and Qiao) with 5 (DG-1), 50 (DG-2), 170 (DG-3) and 400 (DG-4) years’ service time were compared. The results reveal that the natural aging effect weakens the thermal stability of the Dou-gong brackets, leading to an increase in the combustion intensity. Specifically, the DG-4 sample possesses the fastest heating rate and the highest peak temperatures during fire. Moreover, the average charring speed of the DG-4 sample increases from 0.30–0.36 mm min−1 for the DG-1 sample to 0.91–1.00 mm−1 min with increasing service time. Furthermore, the natural aging effect leads to an increase in the damage degree and a decrease in the residual bearing capacity of the Dou-gong brackets, with the residual bearing capacity of the DG-4 sample being 25.5 kN, which is 49.6, 37.5 and 16.1% lower than that of the DG-1, DG-2 and DG-3, respectively. This research is expected to provide support for the fire risk assessment of wooden heritage buildings from the level of the Dou-gong brackets.