Evaluation of effective flange width in the Timber Composite Beams

A timber composite beam consists of a Cross Laminated Timber (CLT) panel attached to a girder such as a Laminated Veneer Lumber (LVL) beam. Under positive bending moment, part of the CLT panel acts as the flange of the LVL girder and resists compression. When the spacing between the LVL girders becomes large, simple beam theory is not applicable because the compressive stresses in the flange vary with the distance from the LVL girder web and the flange area over the web is more highly stressed than the extremities; this phenomenon is termed shear lag. For the design of steel-concrete composite sections, the effective flange width concept has been introduced into national and international design specifications. Despite the large number of studies regarding steel and concrete composite structures, comparative, comprehensive research has not been conducted on timber composite structures. In this study, a numerical model was developed and experimentally validated for analyzing different configurations of timber composite beams. Based on a parametric study, a formula is proposed for determining the effective flange width of timber composite beams.

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