Influence of Pu-zuo on progressive collapse behavior of ancient southern Chinese timber buildings built in the Song and Yuan dynasties: Experimental Research

Ancient southern Chinese timber buildings, built in the Song and Yuan dynasties (AD 960-1368), play an important role in Chinese cultural heritage. Nowadays, such buildings collapse more frequently than before due to local member failures. This study focuses on a special construction arrangement of ancient Chinese timber buildings, called Pu-zuo, and its effect in the progressive collapse of the building is experimentally studied in detail. Five 2-bay frames are designed for this experiment, one without Pu-zuo and four with Pu-zuos, considering different arrangements and types of Pu-zuo. A downward load is applied at the middle column until failure occurs. The progressive collapse mechanism of the frames and the mechanical performance of the joints and components during the collapse process are investigated. Finally, comparing the results between the five frames, the structural effect of Pu-zuo resisting the progressive collapse is studied. The results show that the main beam of the frames, called Lan-e, is a key component to transfer the load to the side columns when the structure collapses due to middle column failure. Compared with the frames without Pu-zuo, the bearing capacity of the frames with column and intermediate Pu-zuos increases by 138%similar to 158% and the one of the frames with only column Pu-zuos increases by 45%similar to 60%. Hence, intermediate Pu-zuos further improve the stiffness, bearing capacity and ductility of the structure in progressive collapse.