故宫同道堂木结构的残损分析及保护建议

Damage analysis and protection of timber structure of Tongdao Hall in the Imperial Palace

古建木结构是华夏民族的宝贵财富,但历经数百年服役后存在不同类型和程度的残损现象,降低了结构的安全性能。选取北京故宫内的同道堂为研究对象,通过现场勘查和残损分析,获得结构柱框层、斗栱层和梁架层中典型的残损类型、特征、影响、数量和分布规律,并对其残损成因进行归纳,提出相应的保护建议。结果表明:结构的残损类型主要包括构件开裂、糟朽、缺失、歪闪、分离和榫卯节点拔榫等,其中,斗栱层残损状况最为复杂和严重;结构残损成因可归纳为材性退化和木材缺陷、生物侵蚀和自然环境变化、长期复杂的荷载效应以及不合理的修缮措施;建立结构健康监测系统、加强生物病害防治、推进木结构力学性能的基础研究等是古建筑保护和修缮的重要基础和手段。

Ancient timber buildings are precious treasure of Chinese nation.However,some of them have suffered different types and degrees of damage after hundreds of years of service,which reduces the safety performance of structures.In this paper,the Tongdao Hall in the Imperial Palace at Beijing is chosen as the research object.Through on-site investigation and damage analysis,the typical damage types,characteristics,influences,quantity and distribution law of structural column frame layer,Dougong layer and beam frame layer are obtained.The causes of its damage are summarized and the protection suggestions are proposed.The results show that the types of structural damage mainly include component cracking,decay,missing,inclination,separation,and pulling-out of tenon joint,etc.Especially,the damage at the column frame layer is the most complex and serious.The reasons for structural damage can be summarized as material degradation and timber defects,biological erosion and variation of natural environment,long-term complex loading effect and irrationality of repair.Establishing structural health monitoring system,strengthening biological disease prevention and control,and promoting the basic research onmechanical performance of timber structures are essential for protection and repair of ancient buildings.