Mechanical Properties of Stress Laminated Timber Decks – Experimental study

Paper in proceeding, 2009

In several European countries, the design of stress laminated bridges has been conducted according to a simplified method developed by M. A. Ritter in the 1990’s, valid for American wood species such as Douglas fir. According to this method a stress laminated deck can be designed as a beam with cross section dimensions beff x t, where beff is a fictitious (or effective) width - determined according to orthotropic plate theory - and t is the thickness of the deck. However, there are several uncertainties concerning the validity of this model concerning its application to European stress laminated bridges. These uncertainties are related to: (1) wood species - in Europe boards or glulam of Norway spruce or Scots pine are generally used; (2) design philosophy - Ritter’s model was developed according to the “allowable stresses design method”, whilst the philosophy behind the Eurocodes is the design method according to the ultimate limit states. In this paper, an experimental investigation on specimens manufactured with pre-stressed glulam will be presented. The glulam is made from Norway spruce. The aim of the study is to estimate the mechanical properties of stress laminated timber decks with varying pre-stressing forces. The methods for measuring (a) transversal modulus of elasticity ET , and (b) the transverse shear modulus GLT will be presented. Comparison with results obtained by this research and results obtained by other researcher will be shown.