Institute for Transportation

Since the Ministry of Transportation of Ontario (MTO) directed its attention towards wood bridge development in the early 1970’s there have been significant advances in technology as a result of their work. Beginning with the development of the Stressed Wood System (SWS) in 1976 MTO has been instrumental in reviving the use of wood bridges across North America. There are probably more bridges being constructed or rehabilitated now, using wood, in both Ontario and the United States (US) than has been performed for more than 20 years.

Over the last 5 years there has been a great deal of development work performed on wood bridges surrounding the SWS system. Work has been performed by government agencies such as transportation and forestry, as well as Universities and several industries. Most of the work has been aimed at longer span wood bridges and much of it has been published in one form or another. However, although there has been some contact between the various groups there exists no consolidation of the varied works.

The objective of this paper is to summarize all the major activities that have taken place using the SWS in both Ontario and the United States. It represents the first stage of a cooperative program between the USDA Forest Service, Forest Products Laboratory and the MTO. These two agencies represent the centres of information and activity on the SWS in the US and Ontario respectively. The paper briefly reviews the development of the Stressed Wood Deck leading into the new longer span concepts being developed using the SWS.