Stress-laminated timber decks in bridges: Friction between lamellas, butt joints and pre-stressing system

Francesco Mirko Massaro,Kjell Arne Malo

doi:10.1016/j.engstruct.2020.110592

Francesco Mirko Massaro, Kjell Arne Malo

Open Access

https://doi.org/10.1016/j.engstruct.2020.110592

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Abstract

Stress-laminated timber (SLT) decks in bridges are popular structural systems in bridge engineering. SLT decks are made from parallel timber beams placed side by side and pre-stressed together by means of steel rods. SLT decks can be in any length by just using displaced butt joints. The paper presents results from friction experiments performed in both grain and transverse direction with different levels of pre-stress. Numerical simulations of these experiments in addition to comparisons to full-scale experiments of SLT decks presented in literature verified the numerical model approach. Furthermore, several alternative SLT deck configurations with different amounts of butt joints and pre-stressing rod locations were modelled to study their influence on the structural properties of SLT decks. Finally, some recommendations on design of SLT bridge decks are given.

Highlights

Stress-laminated timber (SLT) bridge decks were developed in North America in the late nineteen-seventies
The unfilled circles are the measurements from the experiment, while the filled circles represent the results from the simulations
Since the pre-stress becomes uniform after the diffusion length lt from the deck edge, the transverse tensile stress must be limited in proximity of the edge in order to avoid gaps between the laminations

Summary

Introduction

Stress-laminated timber (SLT) bridge decks were developed in North America in the late nineteen-seventies. This deck concept started to be utilized elsewhere, especially in Australia and in the Nordic European countries [1]. SLT decks consist of parallel timber beams stacked side by side, most commonly with their longitudinal direction parallel to the long direction of the deck. The beams (lamellas) are mechanically held together by pre-stressed (steel) rods, installed in pre-drilled holes in the perpendicular direction relative to the grain and lamella axes. Different rods arrangements are employed in recent constructions where e.g. two rows of pre-stressing rods are used (see Fig. 2)

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