Modelling and Characterization of the Structural Behaviour of Wooden Cultural Heritage under Hygro-mechanical Loading

• Applicant: Professor Dr.-Ing. Michael Kaliske
• Subject Area: Applied Mechanics, Statics and Dynamics ; Architecture, Building and Construction History, Construction Research, Sustainable Building Technology ; Construction Material Sciences, Chemistry, Building Physics
• Term: since 2013
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 240287377

Wooden cultural heritage, like historical panel paintings, furniture and music instruments often show damages as large deformations and cracks. The reason are hygrical loadings, that occur due to daily and seasonal variation of the room climate and mechanical loadings, e.g. resulting from tensioned strings of instruments. Within the framework of the project, the long-term analysis of wooden structures under these loadings shall be enabled and, thus, an objective tool developed for decision making in the context of conservation. Critical loadings as well as effects of restoration measures on the structural response can be determined and investigated, without influencing the unique original objects. By predicting the long-term behaviour under future loadings and climate change and by defining tolerable climate conditional limits, the analysis tool can be an important contribution to the preservation of the historical wooden cultural heritage.For the comprehensive long-term structural analysis of wooden objects by the Finite-Element-Method, the development of efficient methods is necessary to consider time-dependent climate loads and structural responses. To enable the simulation of large structures in the long-term range and highly non-linear material models, the computational costs need to be considerably reduced. Thus, a temporal multiscale method for the cellular, natural material wood, the multi-physical characteristics and hygrical and mechanical external loadings is developed.The required constitutive material formulations for the description of the time- and moisture-dependent behaviour of wood are developed within the project. The moisture-induced stresses, creep effects as well as the influence of adhesive joints and surface coatings on moisture transport and mechanical structural behaviour are studied with the help of appropriate experiments. The, until now, widely unknown material properties for time-, moisture- and loading-dependent creep and mechano-sorptive effects as well as micro-scale moisture transport of characteristic wood species, historical glues and surface coatings, used in historical objects, are determined experimentally under consideration of the natural variation. Appropriate physical laws are derived and material models are developed with the help of these experiments.The newly developed methods and models are used for the numerical simulation and structural analysis of the historical objects. The influence of multi-physical loadings and material characteristics on the load-bearing behaviour is captured by means of Finite-Element-Analyses. The results of the experiments and simulations are used to define reasonable changes of room climate within museums that do not cause or intensify damages to the cultural heritage and with that are a potential tool for conservators to evaluate the influence of the climate and predict the structural long-term behaviour of historical objects.

• DFG Programme: Research Grants