故宫古建榫卯节点典型残损问题分析

Typical Structural Health Problems of Tenon-mortise Joints of Ancient Buildings in the Forbidden City

为保护故宫古建筑,采取理论分析与现场勘查相结合的方法,研究了故宫古建大木结构榫卯节点的典型残损问题。基于榫卯节点的构造特征和残损现状,讨论了故宫官式木构古建的榫卯节点在不同因素作用下出现的不同类型残损问题,包括残损问题的表现形式、主要症状、发展趋势、对古建筑的潜在威胁等方面。分析了古建筑榫卯节点产生残损的不同诱因,结合工程实例,提出了加固建议。结果表明:故宫古建筑榫卯节点的典型残损问题包括拔榫、变形、糟朽、加固件松动等,对古建筑的整体稳定性构成了威胁;引起榫卯节点的残损问题的因素是多样的,但主要包括外力作用、木材材性缺陷,以及榫卯连接构造的特点等方面。采取铁件拉接、木柱支顶、碳纤维布(CFRP)或铁件包裹等方法均有利于解决上述残损问题。

To protect ancient buildings in the Forbidden City,survey and analysis methods were used to study structural health problems of tenon-mortise joints of the timber buildings. According to constitution characteristics as well as damage status of the tenon-mortise joints,their typical structural health problems were summarized. Detailed researches were taken on the appearance,characteristics and trend of the structural problems. Causes of the problems were also discussed,and the strengthening suggestions were proposed. Results show that typical structural health problems of the tenon-mortise joints include rot,crack,tenon pulled out of mortise,deformation,invalidation of strengthening material and so on. The problems threaten the stability of the ancient building. Main causes for these problems relate to constitution of tenon-mortise joint,material properties of timber as well as iron,loads and so on. Effectively strengthening methods for these tenon-mortise joints include iron connection,additional support,wrap by CFRP or iron and so on.