Investigation of lightning damage mechanism and flashover channels on glazed roofing tiles of ancient buildings through laboratory experiments

Abstract Glazed roofing components play a very important role in Chinese ancient buildings. In this study, the artificial lightning strike test on a type of glazed roofing tile of ancient buildings in China was carried out to investigate the lightning damage mechanism of ancient buildings. A high-speed camera was used to observe the process of lightning striking the enamel, body and mortar of the glazed tiles. The highest propagation speeds of flashover channel are achieved on the enamel surface of the glazed tile, followed by one on the surface of the body and the mortar successively under the condition of the similar moisture content. The propagation speeds of flashover channels are generally positively related to the moisture content for the same material composition of the glazed tiles except mortar. The flashover channels are basically regular on the surfaces of the enamel and the body, while they are irregular on the surface of the mortar. For the enamel and the body of the glazed tile, the surface flashover is easier to develop along the rough body surface. The lightning current enters the glazed tile easily through the mortar position, which results in the fracture of the glazed tile. The reason might be related to the high porosity, high moisture content and good electrical conductivity of the mortar. So the mortar component of the glazed tiles should be important for the design of the lightning protection, which is helpful to decrease the lightning damage for the glazed roofing components.