The Continuity Of Construction Techniques And Structure Forms Of Dong Drum Tower In Pingtan River Region Of Tongdao County

As the most outstanding public structure,drum tower is the center of Kam(Dong Minority)people's daily life and the clan's symbol.Its distinguishable structural forms in different historical stages reflect the activities and emotions of Kam society,as well as the highest building technology of the time.This thesis focuses on the traditional drum towers in Pintan river region of Tongdao,which is the most representative society of Kam in Hunan.The structural forms and continuity of building technologies of drum towers in modern context is investigated in depth.Firstly,the structural forms and evolution process of local drum towers are investigated.In total 61 drum towers of the 29 villages in Pingtan river region are investigated and surveyed and their layout of foundations,spatial components and framework were identified.Accordingly,new classification methods for drum towers in this region are proposed.Based on the history and distribution of drum towers,three critical historical stages are established: formation stage,adapting stage and mature stage.By comparing the typical structural forms of each historical stage,the main factors that influenced the evolution of the structural forms are discussed.Secondly,the traditional carpenter hierarchy and drum tower building systems are discussed,including measuring scales,the construction team lead by master carpenter,the apprentice system.By combining the “theory of ink” imparted by old master carpenters with large amount of site surveying data,modern geometry knowledge and statistic methods,mathematical models for volumetric design of drum towers are established.Dimensions of main members and global sizes are given in simple equations and tables.Being able to guide the conservation,restoration and strengthening existing drum towers as well as building and optimizating new drum towers,this method significantly imporves efficiency of analyzing and designing local drum towers,Thirdly,the core techniques in building drum towers,the contained theory of ink,and practice model are introduced.Focuses are given to the plotting of Xiang Pole,logic of mortise-tenon connection,fabrication of bamboo sticks,and the unique marking symbols of Pingtan River region.Case studies are also given to elaborate the use of marking symbols during designing the critical mortise-tenon connections and delivery of bamboo sticks.Fourthly,the construction planning and construction technologies for drum tower are studied.By following the sequence of construction planning,site investigation and schedule,quantity survey,foundation building,fabrication of members,erection and correction of framework are elaborately.In the meantime,the rituals closely related to the processes substantially strengthen Kam people's spirits and show their hope for beautiful life ahead.Fifthly,based on the analysis of typical damage observed in local drum towers and evaluation of current codes and status of built vernacular heritage conservation,the critical members,cause of damages and new guidelines on restoration and strengthening are identified.Further,finite element analysis is carried out to study the stress and strain distribution and behavior of mechanical cracks on those critical members.Based on the simulation results,it is proposed to apply stainless steel thinwalled hollow sections to strengthen the mortise and carbon fiber reinforced polymer to strengthen columns and beams.Experimental results show that the combination of above two methods is very effective in controlling the cracking behavior,increasing the post-cracking strength and improving the ductility.Cost-effective,light-weight,user-friendly and short-term,this proposal is practical and applicable to the timbers structures of Kam regions.