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hdpe duct
During the past 20-plus years, designs based on the post-tension
segmental box concept have evolved to become a predominant form
of bridge construction. Critical to safety and longevity of such
structures is the integrity of post-tensioning tendons; however,
during the past five years, instances of tendon deterioration
and failure have been disclosed on several Florida bridges. The
underlying mechanism has been diagnosed as strand corrosion at
grout voids in which bleed water accumulated. Cracking of high-density
polyethylene (HDPE) ducts within which the grouted stands reside
has also been disclosed; and while none of the failures to-date
has been related to this cracking, left unaddressed, access of
moisture, chlorides, and oxygen to the strands will invariably
result in corrosion on the long term. For the purpose of (1) assessing
the cause(s) and mechanism(s) of this HDPE duct cracking, (2)
developing performance based assessment tests, and (3) proposing
a standard for HDPE ducts employed in Florida bridges, a research
project commenced in 2002 that involved investigators at both
Florida Atlantic and Drexel Universities. The project consisted
of 6 tasks: (1) acquisition of new and in-service polyethylene
(PE) cable duct samples; (2) evaluation of material properties
of retrieved and new duct samples; (3) evaluation of duct cracking
mechanism; (4) evaluation of pipe stress crack resistance (SCR)
using performance tests; (5) assessment of current material specifications
for smooth PE duct; and (6) experimental and analytical modeling
of tendon duct cracking.
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needs. You design it, we build it.
hdpe
duct
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