(gentle music)
- [Narrator] Innovative construction
and maintenance practices are an important part of repairing
and preserving our nation's bridges.
The Texas Department of Transportation
with help from the University of Texas Center
for Transportation Research is implementing
more accurate estimates of sheer capacity
of post-tensioned spliced girders,
a cost effective and durable technology
for bridges of intermediate to long span.
These improved estimates cover both the cases
where the ducts are not filled with grout
at the construction stage
as well as the final stage after grouting.
In addition, the implementation provides
full design equations for both cases that will be adopted
in national practice, an area of Texas leadership.
- Commonly pre-stressed concrete bridges have a limitation
of about 150 or 160 foot span length,
and that is defined by the limitations that we have
in transporting these precast girders.
- TxDOT over the last few years has been advancing the use
of what are called precast prestress and post-tensioned
splice girder bridges that use precast concrete.
These structures enable what is usually
the lowest cost bridge super structure material
to span longer than their typical precast
pre-stressed beam cases.
- [Oguzhan] We're giving the concrete industry
a chance to compete with the steel industry to bid on
longer span bridges to where the taxpayers can have
the benefit from the competing bids
to reduce the bridge cost step.
- [Michael] These beams typically have a longitudinal hole,
if you will that is cast into the girders
and it's used either a plastic or metal duct
which is typically about four inches in diameter.
- [Oguzhan] And running high strength steel strands
through those ducts and stressing those.