会议名称：“2021世界木材日”研讨会暨第三届国际林联（IUFRO） 林产品文化研究组讨论会
会议时间：2021年3月21日

报告嘉宾：Bernard Thibaut
嘉宾简介：Works in forest inventory and wood sciences in Cirad (1973- 1978) and CNRS (1980 until now)

报告摘要：
In April 2019 Notre Dame de Paris was partly destroyed by fire. It was decided to proceed to an identical reconstruction and restoration of damaged parts.
Wood issued from 20th century forests should play an essential role in this process, not only for the respect of the old carpenters, but for its noteworthy performances as material for bending strength and its unique environmentally friendly character.
The first operations were dedicated to restoration of stone arch and stone vaulted ceilings assisted by a total 3D digitized description of the monument. Curved glulam beams, perfectly adjusted to stone parts by computer aided manufacturing, can be seen today as spectacular sub-frame for the stone parts consolidation.
The roof frames of choir, nave and spire were made of oak wood from French forests. Spine was constructed in the 19th century by Viollet-le-Duc using oak timber pieces sawn from big and old trees by “modern” machining practices. Choir and nave were built 800 years ago using Middle-Age oaks and innovating techniques.
One of the basis of these Middle-Age building process was the use of full length (10 – 12 m) oak logs issued from very slender trees of small diameter (25 – 30 cm) and young age (50 – 80 years old). The logs were just slightly squared using a specific axe cutting solution and positioned within the frame in green state. The same techniques were used for most of the Middle-Age cathedrals in Western Europe. They proved to be very efficient by eight century’s experience.
Data from the national forest inventory prove that there are plenty of slender oak trees in the required diameter range, in the current French forest. Literature data prove that slender trees have higher modulus of elasticity and higher strength and that round woods have similar mechanical properties as clear wood specimen, which is higher than sawn timber.
Experimental and modelling studies are in progress in order to understand the rationale behind the Middle-Age timber techniques for further monument restoration or new solutions for the use of oak in building.

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