THE ORIGIN OF TIMBER ARCH BRIDGES IN CHINA

Abstract

The main structure of timber arch bridges in China consists of two longitudinal polygonal arch systems made of straight logs. According to their present situation, location, and structural details, these timber arch bridges can be further divided into two types: one is exemplified by the non-extant ancient Bianhe rainbow bridge, and the other by the extant Min-zhe timber arch bridge. However, the historical origin of these two bridges is not clear and is still being argued. In this paper, the two types of timber arch bridges are structurally and historically analyzed and compared to determine which one is the pioneer from the technological development viewpoint. Results of our research indicate that, compared with the Bianhe rainbow bridge, the Min-zhe timber arch bridge has better traffic performance and can provide additional service performance. The spandrel structure, X-bracings as well as inserted wood blocks among logs in the Min-zhe timber arch bridge play important parts in carrying loads and enhancing the integrity and stability of its main structure, while the covering house adds dead load to the main structure to improve its resisting capacity against uplift loads. Therefore, from a reasonable consideration of technological development, the authors support the opinion that the Bianhe rainbow bridge is the origin of the Chinese timber arch bridges.