In-situ evaluation of timber roof structures of historic buildings

Condition assessment is an important step before repairs of timber structure. In the past, the experienced master carpenters carried out these works in Taiwan. This paper addresses the inadequacy of the traditional evaluation method, and proposes a new methodology to evaluate a roof structure by taking into account the structural performance. The method can be divided into three steps, first the visual inspection was conducted to record necessary information for further structural studied. Secondly, the structural analysis of the trusses was carried out in order to obtain the stresses in members. Comparing the resultant stress under loading with allowable stress, safety factor in each member was calculated. Finally, the unsafe and suspect members are designated for further nondestructive testing - the drill resistance. After considering the structural performance of the roof structure and condition in each member, the members that cannot meet the requirement will be found and recommended for replacement. Furthermore, the proper minimum section of each member that should be replaced is also proposed in this paper.