Congress Ave. Bridge Retrofit

pic1Dear Concerned Austin Taxpayers:

I have followed the discussions of rail for many years and am keenly interested in seeing the right outcome for Austin Taxpayers. In 2012 Black + Vernooy did a series of schematic drawings illustrating the concept of an Improved Congress Ave. Bridge that could incorporate Urban Rail, Vehicular, Bicycle, and Pedestrian traffic into a significant part of our civic environment. In our investigations we came across a Structural report done by PE Structural Consultants for the City, analyzing Congress Ave. Bridge and South 1st Bridge as possible streetcar routes.

The Structural Analysis* is a thorough and in-depth document, but this is most relevant regarding Congress Ave. Bridge:

  • “The superstructure was analyzed with the LRV loads in a center running track configuration and the results showed the interior box beams carrying the LRV load to be overstressed by about 28%” – Please take note that a streetcar is more than 40% lighter than the heavier vehicles used in this study.
  • “Based on the results summarized above, it is confirmed that (the Congress Ave. Bridge) can be used to carry LRV trains in addition to vehicular traffic and pedestrians but will require varying degrees of retrofit to do so.”

If you take a look at this load comparisons chart, you will see three different sized vehicles. The first is for the current Red-Line (Stadler GTW; 183,200 lbs.), the Second is the vehicle used to conduct the load analysis for the PE Structural Report (Seimens S70; 121,850 lbs.), and the third is the United Streetcar (100; 85,900 lbs.) currently built in and serving downtown Portland OR. The American made, lighter weight vehicle is a more appropriate choice for Urban Rail.

While the study indicates that the Seimens S70 overstresses the bridge by 28%, you can see in the chart that the United Streetcar is actually more than 40% lighter when fully loaded than the study vehicle. I am certainly not an engineer, and I don’t think that it would be a 1 to 1 reduction comparing weights to effective loads, but I do think that this indicates that we are already in the ballpark if a lighter weight vehicle is chosen (a likely choice as the United streetcar is designed for this exact application.) Implementing what retrofits might be needed for the lighter weight vehicle will be proportionally less in scope and costs.

While Kyle Keahey, a consultant for Project Connect, informed the public that building a bridge or tunnel at Lady Bird Lake for Austin’s proposed urban rail would cost $75 million to $475 million (source), we recommend a simple, time-saving and cost-efficient process of re-engaging the structural capacity of the massive arches that were separated during the 1970’s widening of the bridge deck.

It is my plan to continue to explore the idea of using the existing bridge on Congress to not only save tax dollars for the alignment, but to also serve the populations where they exist and reinforce Imagine Austin’s goal of a compact and connected city by enhancing Congress Avenue, the Greatest Street of Texas.

Sincerely,

Sinclair Black

* Austin Urban Rail Advanced Conceptual Engineering Study Subtask 5.4: Structural Evaluation Study and Preliminary Retrofit Designs for Existing Bridges (May 24, 2011)

In addition to PE Structural Consultants’ suggested usage of post-tension cables, we believe that there may be more cost-efficient solutions that involve engaging the original arch of the bridge:

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If you’d like to learn more about our vision, please click here to view our presentation.

 

 

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One response

16 10 2014
Right Rail, Right Route, Right Costs, Right Reasons | The Placemaking Institute

[…] Congress Ave. Bridge Retrofit = Possible & Cost Efficient […]

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