Key Features:

• Bridge Retrofit
• Concrete Box Culvert

As a City of Austin Civil Engineering Rotation List Assignment, P.E. Structural designed and detailed retrofits for four City of Austin bridges currently in a state of distress or disrepair. In the first phase of work, PESC prepared written reports to provide the City with current status and recommendations for repair.  The second phase of work included developing, designing and detailing retrofit or replacement work.

In particular, the Circle S and Northbluff bridges proved the most challenging investigations.  Based on our observations, these structures date to around 1940 or earlier, and involve rather unconventional construction. 

One end of the existing Circle S Bridge was constructed to bear on the in-situ limestone that lines the creek. This supporting limestone had completely eroded away beneath one corner of the bridge, creating a safety hazard to the public.  We alerted City personnel to this condition and designed a temporary steel pipe shoring post that was installed as an emergency retrofit.  The recommended permanent support entailed drilling two new piers, one on each side of the existing bridge.  A steel wide-flange beam spans between the new piers and restores support to the end of the bridge.  PESC’s recommended retrofit was an economical alternative to bridge replacement.

During our initial investigation of the Northbluff Bridge, we determined that the damage was irreparable and that the bridge should be demolished and replaced.  For economy, a concrete box culvert structure was recommended as the replacement structure.