Research On The Conceptual-design Thoughts And Sliding Collapse Performance Of Chinese Ancient Timber-Frame Buildings

Some of the existing ancient timber-frame buildings in China have been nearly a hundred or even thousands of years. Most of them experienced the impact of earthquakes and natural weathering, but they are still intact as before, showing good structural properties. It is of great importance to investigate the their inherent thoughts of conceptual design and the collapse performances, as it is not only useful to provide a reference for modern engineering design, but also to the protection of ancient buildings.Through the analysis on the design methods, building configuration, structural system and the vertical layers (platform layer, column frame layer, Dougong layer and roof layer), the conceptual-design thoughts in the ancient timber-frame buildings are discussed. The results show that the 3:2 aspect ratio of the Cai in Song dynasty is a most responsible integer ratio to gain the maximum flexural strength when cutting a round wood into a rectangle. The strength of components selected according to Cai-Fen rule is abundant. Plane arrangement of the structural system is regular, symmetric and uniform which is helpful to resist earthquakes. The small height-width ration and vertical backsetting of the building have strong structural meanings. The timber frame connected by mortise-tenon joints is an excellent aseismic system with multiple earthquake-isolation levels and spatial integrity. The foundation treatment using soft ropes and sticky rice in mixing lime and the floating connection between columns and plinths play an important part in earthquake isolation. The timber frame connected by mortise-tenon joints is semirigid, and it has a strong ability in energy dissipation. The modus operandi such as Sheng-qi and Ce-jiao has a special structural function. Settings of diagonal braces between columns can ensure the overall stability of building structures, improve lateral stiffness and transfer horizontal force under earthquake. Structural members such as Ding-tou Gong, Chuo-mu Fang, Que-ti and Jin-gang are set between column and lintel to improve the joint stiffness. Bracket sets play the role of dampers between layers, and have a strong capability in earthquake isolation and shock absorption. Roof construction makes it possible to resist overturning and slippage between roof and column frame. Post-and-lintel beam is a smart treatment to save material.A simplified dynamic model was constituted to analyze the collapse mechanism induced by slippage of column root. The maximum relative slippage was calculated by solving dynamic equations under Gauss white noise input excitation. The ruling condition of slippage was introduced. By comparison of column diameters in Song and Qing Dynasty, it is found that the maximum slippage never exceeded the radius of the surface of the plinth even as the PGA (peak ground acceleration) reached 1000gal, so collapse due to slippage between column and plinth does not occur. This illustrates that Chinese ancient timber-frame buildings have an excellent capability in resisting sliding collapse.