(soft music) (logo whooshing)
- [Announcer] Recent updates
to AASHTO Bridge Design Specifications
allow for the use of high-strength reinforcing steels
with yield strengths up to 100 KSI.
80 KSI and 100 KSI steels are available,
but questions about durability, cracking,
and how to best use these materials
have prevented their full adoption in Texas.
The Texas Department of Transportation
and researchers with the Center for Transportation Research
examined bridge components to identify
where these high-strength steels
could benefit Texas bridges.
- Grade 40 reinforcing steel was followed
by the current standard Grade 60 reinforcing bars,
and now development basically carries on.
And Grade 80 and Grade 100
and those numbers imply the yield strength
of the reinforcing bars is getting into the marketplace.
And the availability of these new materials
had to be investigated prior to deployment
in projects within the state of Texas.
For service-related questions,
the best tool that we can use is large-scale testing.
So the research took place
at Ferguson Structural Engineering Laboratory
because the questions that we're trying to tackle are:
If you're using this high-strength material
and lesser quantities of it,
the cracking that can occur under service conditions,
is that gonna be any worse, similar to,
or better than what we have in the case
of conventional materials that we're using right now?
So we tackle that goal by conducting large-scale testing.
For the second part,
which is the strength piece,
there are two different components,
and that is we have barriers within the design codes
that will specifically call out and say
the code provision that you're using
for this purpose or that purpose is valid up until 80 KSI,
60 KSI, some other limit,
which establishes the boundaries of our knowledge.
And by eliminating those boundaries
through large-scale testing,
we were able to tackle
those strength-related questions as well.
In a nutshell,
the use of Grade 80 and Grade 100 reinforcement,
so high-strength steel,
within Texas reality is very much possible.
And testing results that we have gathered
basically support the deployment of these new materials
in cases where they are used make sense.
So these new materials,
when they get in the marketplace,
it's not one size fits all.
In some cases where we have congestion
in the reinforcing bar cages,
in cases where we would like to use
this higher-grade material but a lesser quantity of it,
at the expense of spending a little more money
on the high-strength steel but a lot less money
on the labor side,
we may be able to justify its use.
And it's the next tool in the toolbox
that's available for bridge designers and contractors alike.
- [Announcer] For more information
and to find the publications for this project,
please visit the TxDOT Research Library
at the link shown below.