engleski

Round holes in members made of glued laminated timber. Part 2: Load capacity and design

The design of unreinforced holes in members made of glued laminated timber (GLT) is handled very differently in German and European standards and draft standards. The methodology based deficits of the design according to DIN 10522004 and especially the lack of design equations in Eurocode 5 initiated a research project comprising extensive tests with GLT building components and the development of a new design model, The influences of the parameters - beam depth, relative hole size, section force ratio and beam curvature - were investigated with a sample size of 68 bending members in structural dimensions. Essential experimental results consist in the description and classification of the stepped damage evolution and in the quantification of the load capacity effect of the mentioned parameters. A significant size effect has been confirmed. Tension stress perpendicular to grain direction was identified as the primary crack initiating action. The location of the crack on-set at the periphery of the hole is essentially determined by the cylindrical anisotropy of the material. An easily applicable design procedure based on Weibull theory was derived, accounting for the essential influences on load capacity, including the size effect and the inhomogeneous stress distribution at the periphery of the hole. The new experimental well substantiated design model works especially for holes in members with larger cross-sectional depths (1-2 m) more accurate design verifications as DIN 1052:2004 forwarding too high load capacities for large sized members with holes

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