Influence of cracks on the stiffness of timber structural elements

Cracks in timber structural elements lead users to downgrade them, while their influence on the mechanical properties is globally unknown. They are thus disadvantageous and responsible for an underutilization of timber in new constructions. The phenomenon also impacts constructions subjected to transformation or renovation that are most of the time fully replaced, simply because of the ignorance of their bearing capacity. The present paper investigates the influence of cracks on stiffness, by analytical and numerical developments. It proposes a classification of cracks in six types (+ composite types) and models real beams, randomly cracked. It shows that the presence of cracks seems to decrease the stiffness of the beam. However, it is not so obvious to give the most damaging type of crack, among the six proposed. Further investigations will be necessary.