Quantitative Study on Wood Rot and Mathematical Modeling for Predicting Damage in Wood Structures

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Research results are composed of the following two terms.1. Experiments on wood decayPrincipal members of the investigators had visited famous laboratories in Canada and Germany and surveyed the state-of-the art researches about wood decay. On basis of these surveys, Hygro-thermal simulations were performed to predict temperature and humidity inside insulated wood-frame envelopes. Experimental conditions in temperature and humidity were defined using these simulation results. Long term experiments on wood decay had been conducted under those conditions. In these experiments, periodical observation of wood specimens regarding mould, activity of rot bacteria, color change and deformation was carried out, and measurements were also done in weight and dimension. In addition, mechanical strength, such as longitudinal compressive strength, was measured every month after drying out wood specimens2. Formulation of biological damage function on wood productsBy analyzing the above experimental results, knowledge about wood decay was systematized. New biological damage function was formulated according to that knowledge and is also a goal of this project. In the damage function, damage is expressed with durability deterioration. Furthermore the durability deterioration is indicated by degree of decay. Finally degree of decay is formulated with moisture content, time equivalent to hypha growth and so forth, which is an important result of the project. Consequently the damage function enables engineers and designers to predict degree of decay and durability deterioration in wood products numerically, if they will conduct hygro-thermal simulation in insulated envelopes and can obtain temperature, humidity and moisture content.