Abstract
Detailed measurements of drying fissures were carried out on 28 pieces of gross cross-section structural Scots pine timber. Different parameters have been proposed to measure their magnitude: length, depth, thickness and slope of grain, as well as an index of area in the neutral axis plane (ratio of effective to total surface). The parameters of fissures have been related to bending strength, shear strength, modulus of elasticity and rupture energy obtained from mechanical tests, considering whether rupture is due to bending or shear. All of the fissures observed allows to classify the pieces as MEG according to the UNE 56544 standard. To quantify the magnitude of fissures the index of areas is proposed, while mechanical properties can be quantified by rupture energy. Analysis of the results does not show any relation between the fissures analyzed and the mode of failure, their magnitude and mechanical properties..
Highlights
Mechanical properties of timber specimens with fissures have been evaluated for many years
In 1934, the Timber Mechanics Section of the Forest Products Laboratory in Madison carried out a research review to analyze the shear strength evaluation methods used until for the load-carrying assessment of timber pieces (8-9)
The first satisfactory approach to the real problem was achieved through the theoretical analysis of fissured beams and the subsequent testing of 200 specimens, each made of 5 glued timber pieces, while keeping artificial side fissures in the middle plane of the section depth
Summary
Mechanical properties of timber specimens with fissures have been evaluated for many years. In 1934, the Timber Mechanics Section of the Forest Products Laboratory in Madison carried out a research review to analyze the shear strength evaluation methods used until for the load-carrying assessment of timber pieces (8-9). Shear load-bearing capacity of fissured beams obtained by means of testing (those pieces showed shear failure mode) was much higher that the values estimated by usual shear strength calculation methods. The first satisfactory approach to the real problem was achieved through the theoretical analysis of fissured beams and the subsequent testing of 200 specimens, each made of 5 glued timber pieces, while keeping artificial side fissures in the middle plane of the section depth. A reduction of 4/9 of the strength is applied; this factor represents the reduction in load capacity due to concentration of stress at the end of the checks
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