April 15, 1999
Experimental Verification of Prestressed Concrete I-Girder Bridge Behavior
by
Dr. Jeffrey A.
Laman
Assistant Professor
Department of Civil and
Environmental Engineering
This study presents the results
of field tests conducted on three prestressed concrete I-grider bridges to
obtain dynamic load allowance, girder distribution factors, service level
stresses and data for examining analytical grillage models. The tested bridges
have span lengths of 10.3, 23.3 and 31.1 m. Bridge response was measured at the
bottom of each girder near the midspan for the passage of normal truck traffic
and tandem-axle test trucks of known weight and configuration. A numerical
grillage model was developed for each tested bridge. DLA values are seen to be
a function of the peak static stress, and vehicle speed but not span length.
DLA values are highly variable for vehicles with a given number of axles. GDFs
for one and two-lanes loaded are less than GDFs specified by the American
Association of State Highway and Transportation Officials (AASHTO). Results
from the analytical grillage models match experimental data well. Finally
service level stresses extrapolated to 0.5 to 75-year levels are seen to exceed
levels induced by an HS-20 truck in interior girders only.