Manufacture and Assembly Mechanism of Dougong

Abstract

Dougong [斗栱] is a bracket between column, beam, and rafter in traditional timber structure building in China. It has several bearing blocks, named dou [斗], and some bracket arms, named gong [栱]. All components are connected by sunmao [榫卯]. It was born from the capital and later developed into a bracket that does not have to be related to the column. During the last 3000 years, its status in traditional architecture has been rising. In the Qing Dynasty, the architectural design work started it as the core. The chief aim of this research is to explore the possibility and key issues of using dougong for the prefabricated buildings. This research documents a folk building project in China from three aspects: the construction organization, the dougong component manufacture and assembly. After that, we study the mechanism and analyze the traditional technology. Finally, the study provides some suggestions for the prefabricated building. The first aspect is the construction organization. The component manufacture team needs more specialized skills than the assembly team. The two teams exchange information through the code on components and simple language. The proportion of dougong manufacture workload on the standard floor is 40%. The second aspect is the dougong component manufacture. A master carpenter, a chief engineer, is in charge of three tasks: architectural design, material requirements planning, and templates making. After that, he directed 4 carpenters to make components accorded with the templates. The dougong components are universal. Besides, carpenters assemble and code the completed gong components in layers in the carpentry yard. Each layer of gong uses 1 English capital letter to code. The other components are unassembled and uncoded. The third aspect is the dougong component assembly. The assembly team’s workers need only simple skills to complete their work. Limited by the low precision of the hand-made method, they need to fine-tune the size of the gong at the joint between the gong and the column. In this project, the lowest component of dougong is gong, so, the workers assemble 5 layers of gongs into the columns from bottom to top first, and then assemble several dous between the gongs. The completed sunmaos at this stage are not tightly fitted, which leaves room for adjustment of the upper components of the dougong. The research we have done indicates that compared with the assembly stage, the manufacturing stage is a concentrated section of the technology and workload. So, the key to modernizing traditional buildings is the modernization of this stage, especially the dougong manufacture. If it is realized, we can save at least 40% hand-made workload of the standard floor. At the same time, the components will achieve higher accuracy, which is beneficial to improve the assembly speed and quality. Also, in the future, BIM can be utilized based on the traditional design method, which is significant to the inheritance and improvement of dougong technology.