基于木蜂筑巢习性的古建筑木构件木蜂危害等级划分

Evaluation of Damage Grades for Wooden Components of Ancient Buildings Based on Nesting Habits of Carpenter Bee

【目的】基于木蜂筑巢习性,划分古建筑木构件木蜂危害等级,为古建筑保护工程勘察提供参考依据和评定标准。【方法】收集受木蜂危害的轻木构件,采用内窥镜、CT扫描和巢穴解剖方式,了解巢穴构造,计算隧道容积和巢穴体积,估算木材损失程度,结合古建筑木构件危害勘察,划分木蜂危害等级。【结果】经鉴定,收集到的木蜂为黄胸木蜂。内窥镜可以观测到主隧道,隧道有2~3条分枝,次隧道与主隧道夹角成一定角度,影响内窥镜进一步深入观测。CT扫描能够准确了解巢穴内部危害。巢穴解剖发现,黄胸木蜂巢穴皆为分枝型,大部分为双向平行2条分枝或一侧2条分枝另一侧1条分枝;巢室内径平均1.55 cm,每条分枝长度平均14.4 cm,隧道容积平均约133.67 cm^(3),巢穴体积平均1436.58 cm^(3)。【结论】古建筑木蜂危害一般发生在建筑外部的檐椽、望板、斗栱等非承重和非独立作用构件上,基于木蜂筑巢习性估算木材损失程度,古建筑木构件木蜂危害可划分为1~4级:当木构件有且仅有1个木蜂孔洞时,为1级危害;当木构件有2~3个木蜂孔洞时,为2级危害;当木构件有4~5个木蜂孔洞时,为3级危害;当木构件有6个及以上木蜂孔洞时,为4级危害。

【Objective】Carpenter bees nesting on wooden components of ancient buildings brings damage to wooden structures.This study evaluated the carpenter bees damage grade for wooden components in order to provide a basis and an evaluation standard for the investigation and maintenance design of ancient building protection engineering.【Method】Balsa woods damaged by carpenter bees were collected,then inspected nest structure by endoscopy and CT.Then the wood was cut through to observe the nest cell structure.Damage degree of wood structures was converted by tunnels volume and nest size.【Result】The carpenter bee collected in this study was identified as Xylocopa(Koptortosoma)appendiculata.The endoscope could observe the main tunnel,and it could be found that the tunnel had 2-3 branches.CT scanning could provide an accurate understanding of nest structure.By dissecting the nests,it was found that the most nests of X.appendiculata were two parallel tunnels in two sides perpendicular to the entrance hole or two tunnels on one side and one on the other side.The average internal diameter of the tunnel was 1.55 cm,and the average length was 14.4 cm.The average of tunnels volume of each nest was 133.67 cm^(3).and the average of nest volumes was estimated at 1436.58 cm^(3).【Conclusion】The damage of carpenter bees in ancient buildings generally occured on the non load-bearing and independent wood components such as rafters,roof boarding or brackets.In order to estimate the degree of damage,this study evaluated the carpenter bee damage grade as 1-4 rate based on nesting habits:the wood component is found only one hole,it is classified as class 1 damage;when 2-3 holes are found,it is classified as class 2 damage;when 4-5 holes are found,it is classified as grade 3 damage;when more than 6 holes are found,it is classified as class 4 damage.