InTrans / Aug 14, 2018

Perception versus reality: An analysis of timber bridge performance in the United States

Bridge material selection is one of the most difficult
decisions an engineer has to make. Many factors and
individuals are often involved in choosing the proper
bridge material for a given site and location. Not only
physical factors such as strength or lifespan of material,
but also site specific factors like roadway alignment and
traffic count play important roles in material selection.
It is not uncommon for state Department of
Transportation engineers, private consulting engineers,
and local highway officials all play roles in the material
selection process. Each individual may have his/her
own perception of bridge materials based upon past
experience and education. And little is known how
these perceptions influence the choice of materials. In
this study perceptions of engineers and highway
officials toward timber as a bridge material were
compared to the actual performance of timber as
reported in the National Bridge Inventory. To
accomplish this case studies were conducted in four
selected states. Highway officials and engineers in
Mississippi, Virginia, Washington, and Wisconsin
were surveyed by mail and personally interviewed to
capture their perceptions toward timber as it compared
to other major bridge materials (prestressed concrete,
steel, and reinforced concrete). This information was
compared with the actual performance data obtained
from the National Bridge Inventory. The results
indicate that there is a strong correlation between
highway officials‰Ûª perceptions towards bridge materials
and the reported performance of these materials.