Modelling the Bending Strength of Timber Components - Implications to Test Standards

Authors

Jochen Köhler, Markus Sandomeer, Tord Isaaksson and Bo Källsner

Abstract

The present paper focuses on the prediction and modelling of the bending capacity of timber structural elements. The standardisation of test procedures is the prerequisite to compare and aggregate data of timber strength and stiffness related properties on a national and international scale. Concepts of hierarchical modelling are applied to link the information from (mainly standardized) tests to a generic and probabilistic description of the strength and stiffness related capacities in structures; differing in terms of size, climate and load characteristics. A model framework is suggested where three different hierarchical levels of spatial variation of the bending capacity are differentiated, namely the macro variability between different lots of timber structural elements, the meso variability within one lot of structural timber elements and the micro variability within one particular structural element. The results of standard tests are reflecting the variability of strength properties at a meso level. It is discussed how the suggested model framework might be utilized for the consistent representation of
test data. The paper is concluded with a comparison of the impact of weak sections on different standardized test procedures. Monte Carlo simulation technique is used to test generated test data virtually according to three different test standards: EN 408, ASTM D 4761 and AUS/NZ 4063. Possible implications for further developments of test standards for the timber bending strength are discussed.

Published in/by

Proceedings, CIB-W18, 42nd meeting, Zurich, Switzerland, August 25-28, 2009, paper 42-6-3