Bolted and Dowelled Connections in Radiata Pine and Laminated Veneer Lumber Using the European Yield Model

Abstract

Connections with mechanical fasteners are important for all cases of timber structures. The failure of these connections may occur in either ductile or brittle manner. For the calculation of the ductile failure strength or the load carrying capacity, the European yield model (EYM) is used in many standards and accepted as a very accurate model. In the current New Zealand timber standard NZS 3603:1993 (Standards New Zealand, 1993) and the Australian one AS1720.1–1997 (Standards Australia, 1997), the design concept for bolted or dowelled connections is not based on the EYM, and depends only on the diameter, the timber thickness and the species group. The most important parameters for the EYM are the fastener yield moment and the timber embedment strength, but embedment strength values are not available for New Zealand Radiata pine or laminated veneer lumber (LVL). To obtain the missing information and to implement the EYM into the New Zealand and Australian standards, embedment tests parallel, perpendicular and under various load-to-grain angles with different dowel diameters in Radiata pine lumber and LVL were conducted and compiled to build a database of embedment strength values. This paper includes the latest results of the investigations with dowel diameters extended up to 30 mm. Furthermore, different international testing standards are compared and their evaluation methods are used. The test results are also compared with the corresponding results using the Eurocode 5 formulas, and show that adjusted formulas of the Eurocode 5 can be used to predict the load carrying capacity of bolted and dowelled connections in Radiata pine lumber and LVL. Design examples comparing the current methods from the New Zealand/Australian design standards and the proposed method adopted from the EYM of the European design standard are given as well.