(dramatic music)
- [Narrator] Pre-stressed concrete beams
are used in many bridges across Texas.
The American Association of State Highway
and Transportation Officials, or AASHTO,
provides strength requirements for these beams
based on past tests,
but advancements in concrete materials
have brought about the need to reexamine the specifications.
The Texas Department of Transportation
and researchers with Texas A&M University
have looked at the minimum sheer reinforcement requirements
for pre-stressed concrete beams to determine their accuracy
and develop design guidelines that could lower costs
and speed up bridge construction.
- As we progress in the field
and we have new materials, for example,
high-strength concrete, we have high-strength steel,
also, we have larger members, larger cross sections,
there is a natural need to reevaluate
if those requirements that have been based on,
I would say, older designs are still valid
or if we should look at those again and refined.
- So we felt it is needed to take the advantage
of this advancement to revisit
the minimum share enforcement requirement
that we use to design or enforce concrete beams.
If we are able to do that,
that could lead to significant savings,
and that can also help us to have a better approach
in designing of bridges in the state of Texas.
- There was one part of the research
that was data analysis and model development,
so that was essentially analyzing a database.
The other part was finite element analysis,
because we realize that we need to expand our database
and we realize that we definitely need to do some testing.
However, the testing is much more expensive,
so we need to be careful to select, to investigate,
I would say, the most important variations.
So a portion of this extra case evaluation
was done in the lab, and we test, actually,
22 designs in 11 girders, and these girders were quite big,
so we're talking about 50-feet long girders on average,
so quite large specimens.
In addition to that,
we developed finite element analysis models,
where we calibrated them with existing test data
and then we used them to run analysis
on cases which were not in the database,
but were not in the lab either.
- In test docs, as we continue to strive for quality,
as we continue to improve and fine tune our process
of designing bridges,
we continually make use of research effort,
and from that research, we can come back in the department
to refine those research outcome
and see how we can implement it,
because this implementation will bring a lot of cost saving
in terms of dollar cost,
and also in terms of road user cost,
and in terms of a delay that are typically being observed
during bridge construction across the state.
So that is the major benefit of this research,
and it is a continuous effort
that we'll continue to improve on.
- [Narrator] For more information
and to find the publications for this project,
please visit the TXDOT Research Library
at the link shown below.