Alternative Support Systems for Cantilever - National Transportation ...

comments and recommendations on preferences from the options selected in FDOT Report
BD545 RPWO #54 as well as suggest any additional designs. Based on the information gathered
from ISA’s Mechanical and Structural Subcommittee, the pipe with welded studs seemed to be a
preferred option. The subcommittee commented that this detail had been used in larger pipes
from 48 inches to 96 inches in diameter.
2.4 Selection
The purpose of the literature review and investigation into alternative support structures
was to identify viable foundation alternatives on which to conduct an experimental program. The
primary consideration taken into account for the selection of the alternative support system was
its ability to properly handle the loading configuration present in a cantilever sign/signal support
system. Constructability, time, and expense were taken into consideration, though not fully
explored. The foundation systems of other industries were investigated and considered.
Some of the least viable options were the drilled helical pipes, the soil anchors, and the
piles. These options would not only be expensive, they would likely not sufficiently handle the
loading conditions encountered by the foundation of a cantilever sign/signal configuration. The
cast-in-place options seemed most viable as they are the currently used design and seem to be
preferred by industry professionals. They can sufficiently handle the loading conditions, are less
expensive than other options, and can be easily constructed.
While the investigation into other industries provided insight into how different industries
are addressing issues with shear, biaxial bending, and axial load, they do not necessarily provide
solutions to implementing a design to transfer torsional load from the steel to the concrete. The
recommended cast-in-place designs from FDOT Report BD545 RPWO #54 are the designs with
the most potential for applications of sign/signal foundations (1). Therefore, the recommendation
for potential design was the pipe with welded plates. The clear load path associated with this
21