(graphic whooshes)
(pensive music)
- [Narrator] Many Texas bridges use
simple span girder decks.
But because of expansion joints in these type of bridges,
issues with durability and maintenance can arise.
An approach to intentionally form cracks
called a Texas Poor Boy method has been used for decades.
But there is no comprehensive assessment of this technique.
Researchers with the Texas A&M Transportation Institute
and the Texas Department of Transportation
surveyed the performance of the current bridge methods
to make recommendations on new construction
and rehab designs.
- When you're building a bridge, you've got multiple spans,
and between those spans, there's a gap
between the ends of the girders.
This is intentional and it allows for thermal expansion.
- With the weather in Texas being hot and cold,
hot and cold, the bridge is actually gonna move quite a bit
and want to expand and contract.
So that's what the joint is there for.
- [Anna] These often involve lots of maintenance
and can allow water through
that can eventually damage the substructure
beneath the bridge deck.
- [Daryn] Ultimately, what we would like to do is,
we like to be able to remove that joint from a bridge system
and just make those spans continuous all the way through,
which would be no joint from start
of the bridge to the end of the bridge.
- [Anna] Have the deck be continuous over the gap
and hence the name continuous deck detail.
Because the girder deformation introduces stresses
into the continuous deck,
there are unique design considerations
for this portion of the bridge deck
relative to the rest of the deck.
- [Daryn] We were able to build a computer model
that showed the initiation of the cracks.
Then we were able to take that into the laboratory
and replicate that exact data into the full scale models.
- We had students build four bridges
with six unique designs on them.
Two designs replicated existing details,
two designs implemented retrofits,
and two designs were proposed new designs.
The new designs were selected for testing
based on the results of dozens
of options investigated in the computer models.
The benefits of full scale tests is replicating
the exact details in Texas Bridges.
Such details have been absent from prior research
on links labs, yet these details are critical
to where cracks develop and how severe they are.
But the test successfully replicated damage
in existing bridges with the new designs shown
to improve the performance greatly.
One aspect of the new designs is to allow
for more flexibility of the deck.
Another aspect of the new designs
is eliminating some details
that allowed cracks to initiate.
- So the benefits for the department would be,
we get to eliminate that expansion joint
or the need for that expansion joint,
which would then further reduce our maintenance cost
and a few headaches in the future.
For the traveling public, this would also mean
that we could probably have a smoother riding bridge.
When you obviously have to put in that expansion,
you have to start your concrete placement
and then finish at the joint
and then start back up at the other side of the joint.
So that kind of gives it that, the bump
in the middle of the bridge usually.
So we would be able to get away from that
and actually have a continuously graded slab
so it would be a little bit smoother.
- [Narrator] For more information
and to find the publication for this project,
please visit the TxDOT research library
at the link shown below.