Testing and Evaluation of
Basket Handle Arch
Hangers, I-235 Pedestrian Bridges
About the research
This research involves the rationale for, and results of, structural
monitoring of two steel basket-handle arch pedestrian bridges which were constructed in stages to
minimize traffic disruptions.
These bridges utilize a hanger system consisting of high-strength
threaded steel rods to support
the precast, post-tensioned concrete deck system.
The research team used externally-mounted accelerometers to monitor the
free vibration of each
hanger during all incremental construction stages as well as one year
after completion. The
acceleration records for each hanger were analyzed using a fast fourier
transform (FFT) to
calculate the natural frequency of several modes of vibration. These
natural frequencies were
then used to estimate the tensile force in each hanger considering both
taut-string theory and the
flexural stiffness of the steel hanger rod.
The results of this work show the value of structural monitoring during
construction and indicate
that some moderate changes in structural behavior occurred after the
bridge entered service.