Evaluation of strength and stiffness of wood components damaged by xylophages

Abstract:

This paper evaluates the strength and stiffness of structural wooden components considering biodeterioration, that uses a model of strength and stiffness related to bending. Mechanical properties of sound wood were estimated from wood identification and correlation of density with mechanical properties. The effect of slope of grain was included using Hankinson-type formula. Four models to evaluate the damage on mechanical resistance and stiffness were developed based on strength of materials, considering the type and intensity of biological attack. Damage caused by knots and weatherings were not considered. Types of attack and intensity were analyzed taking account fungus, termite and wood borer: exterior decay (model 1), interior decay (model 2), uniform decay (model 3) and sapwood decay (model 4). The intensity of biological attack was divided into six groups: sound wood; initial attack (up to 20% of cross section); moderate attack (20% – 40%); intense attack (40% – 60%), very intense attack (60% – 80%), and destroyed (over 80% of cross section). Different thickness of attack along the cross section of wood was considered for each group. Even for the same attack level in area, geometry of attack influences significantly the bending strength and stiffness in major direction. In summary, models 2 and 3 presented the best results in flexure strength and stiffness, but the evaluation of parameters of model 2 is less reliable than of models 1, 3 and 4. This fact is important, because the external portion is easier to evaluate than interior portion of wood.

Reference:
YOJO, Takashi; SOUZA, Cassiano OLIVEIRA de; MIRANDA, Maria José de Andrade Casimiro; LOPEZ, Gonzalo Antonio Carballeira. Evaluation of strength and stiffness of wood componentes damaged by xylophages. In: JORNADAS SUDAMERICANAS DE INGENIERÍA ESTRUCTURAL, 38., 2018, Lima. Proceedings… 9 p.

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