The benefit of having a concrete deck has been demonstrated in the paper by Greg Nolan. From investigation of existing timber bridges with concrete decks it has been demonstrated that the timber beams can be effectively protected from rainwater and as a consequence there is much less decay. It can be concluded that the life expectancy of concrete decked bridges can be two or three times longer than timber decked bridges, that is 50 to 75 years, making such bridges "permanent" rather than "temporary" construction.
The benefit of composite action between deck and supporting beams are well know and exploited in concrete and steel construction. The benefits of composite action in concrete decked timber bridges are significant. Composite concrete and timber bridges have been built in the USA and in New Zealand for many years and more recently in Australia.
Having demonstrated the effective protection provided to timber bridges by a concrete deck the use of composite construction would seem to follow logically.The following paper presents some results from experimental research into composite construction with manufactured beams and unseasoned natural round timber beams.
To see the full paper, click here.