Institute for Transportation

In 1988, the U. S. Congress passed legislation known
as the Timber Bridge Initiative (TBI). The purpose of
the legislation was to establish a national program to
provide effective and efficient utilization of wood as a
structural material for highway bridges. As part of the
TBI, a demonstration bridge program was developed
to enhance rural America by encouraging innovation
through the use of new or previously underutilized
wood products. In south-central Iowa, two counties
have constructed stress-laminated timber bridges using
eastern cottonwood, a local, underutilized species.
This paper presents a summary of the performance of
three stress-laminated eastern cottonwood bridges
constructed in 1994.