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(upbeat music)

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- [Instructor] Thanks to
some of the latest research

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from engineers with the Center
for Transportation Research,

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bridge designers can now build
more economical structures.

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As part of this project

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a new analytical method was developed

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that proves TxDOT bridge beams

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have a higher load carrying capacity

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than previously thought.

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- So in our current analysis method

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there's a provision in the spec

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that limits the shear
stress at our beam ends

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and when we exceed this, the spec tells us

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that we have to do a
strut-and-tie analysis.

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The strut-and-tie analysis is
very calculation intensive.

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So most designers opt to not do it

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and just add in a beam line
to reduce the shear stress.

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So adding in this beam line
adds cost to the project.

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- If you can permit a
higher level of shear stress

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in a typical bridge design
where the span lengths

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are being pushed to their extremes,

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you can actually eliminate a beam line.

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And if you're eliminating
a beam line in this bridge,

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a beam line in the next
bridge, and some other bridges

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before you know it with those settings,

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you can construct another
bridge to serve communities

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faster, better in the state of Texas.

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- So what we did here is
we had the researchers

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look at the strut-and-tie
models of all the beam ends

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of all of our standard beams

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and let us know when
the strut-and-tie model

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tells us that you can't go
above a certain shear stress.

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- We constructed a variety

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of different strut-and-tie models

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for different types of standard
precast concrete builders

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and we were able to change
that limiting shear stress

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from 18% to some cases

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where we can go all way up to 25%,

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in other cases greater
than 18 but less than 25.

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- This will help us reduce
the number of beam lines

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which will reduce the cost of projects

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specifically on projects

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where we're stretching the span limits.

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- The result of this work
can really be summarized

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and has been summarized in a simple table

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where a TxDOT will be able to better use

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its precast concrete sections
to their actual capacities

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as opposed to the more conservative

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way of handling this problem.

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- This is a really early stage.

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The research has just completed.

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So we need to review it in house

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and determine how we're
going to implement it.

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Right now the researchers have suggested

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different stress limits
for each individual beam.

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So it's likely that we
would combine them together

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and make it a bit more simple.

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- [Instructor] For more information

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and to find the publications
for this project

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please visit the TxDOT Research Library

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at the link shown below.