The interest in, and momentum for use of, timber bridges has been growing in the last few years and is expected to mushroom in the near future. This trend effectively reverses the declining trend of the last four decades. Why all the sudden interest? There are four broad reasons, termed driving forces, that are generating the interest. These driving forces are (a) economic development (especially rural), (b) awareness, (c) need, and (d) the new stressed timber concept. All of these driving forces are examined and the concept of stressed timber for bridges is expanded. The u.S. Congress appropriated $3.35 Million to continue research on stressed timber bridges and construct 80 demonstration bridges across the nation in 1989. That funding level was maintained in 1990. Stressed timber is catching the eyeof innovative bridge engineers across the united states. The progress of stressed timber and the potential for its increased use and more innovation are greater than ever. Stressed timber is not new; in ontario, canada, stressed-timber bridges are more than 10 years old and show outstanding performance characteristics. The process of approving aashto standards for stressed-timber bridges has begun. This paper appears in transportation research record no. 1291, Fifth international conference on low-volume roads, may 19-23, 1991, raleigh, north carolina, volume 1.
Samenvatting