salvageable. The County wanted the design of the new
structures to maintain the original character of the railroad
trestles. The way to do that is through unique design
details, said Hisham Sunna, PhD, PE, principal-in-charge
for Ayres Associates. “The aesthetic details are what
connect the new bridges to the history and the location,”
he said.
Designers came up with several key details to help
make the pedestrian trail bridges look more like the old
railroad trestles, starting with the pilings that support the
structures. The pilings are unique in their shape, color, and
placement. Designers chose 16-inch round piles rather than
more typical piles like 24-inch square. The concrete itself
was dyed to look older and darker – more like the old
railroad bridge. “Because some of the characteristics of
this structure are completely unique, it was challenging to
find a fabricator that was willing and able to create them,”
said Steven Laney, PE, Ayres Associates’ supervisor of
structural engineering. An added benefit of the dyed concrete
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is that it would require less maintenance without the need
for repainting, he said.
The number and spacing of the bridge supports were
also purposely designed to mimic the old railroad
structure. While today’s typical trail bridge may have only
two pilings in each bent, the Roberts and Dona Bay
bridges have five to seven pilings that were placed similarly
to the old railroad bridges.
Perhaps the most striking feature is the look of railroad
ties along the profiles of the bridges. “The contractor and
the fabricator built a concrete form that would essentially
stamp an indentation at regular intervals and recreate the
look of the ties,” Laney said.
The new bridges are better for the water quality and
habitat in this delicate area. “The old trestles were
creosote-soaked lumber, and removing them was the best
thing that could’ve happened environmentally,” Boudreau
said. Creosote is a wood preservative that may have harmful
health and environmental impacts.
TRENDS
TRENDS
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