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Case Studies
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The culvert on Sylvan Ave. was just one small part of a very large Texas Department of Transportation freeway expansion project constructed in multiple phases over several months. The original culvert design called for a double-barrel run of 20 ft x 12 ft, 156.5 ft long to be placed alongside an existing, dog-legged, 30-ft span CIP culvert structure constructed in the year 1934. There is very little headroom at this location (from 0 to 3.5 ft), ideal for a CrownSpan installation. Each three-sided bridge unit weighs 29.7 tons and are available in stands of 14-40 ft and rises of 3-12 ft.

However, Gilbert Texas Construction L.P., the prime contractor, discovered that they could remove an entire phase from the construction of the main lanes if they could construct a temporary access tunnel under the temporary main lanes of the freeway to move their equipment through during that phase of the project, so the revised plan was to use the CrownSpan units for a temporary bypass.

At first, the plan was to have Hanson Pipe & Precast redesign eight units to withstand 13 ft of fill, but, deciding crews could use the extra headroom for their heavy equipment, it was decided to use the CrownSpan units as originally designed and raise them up to grade by placing them on elevated footings that the contractor designed.

After the footings had been constructed, the first eight units were delivered during the night due to heavy daily traffi c volumes and safety concerns. Units were delivered on their sides in order to lower their center of gravity.

The delivery of CrownSpan units to the project location began in October 2004, and after seeing daily traffic volumes of around 150,000 for about 15 months, the eight temporary units were relocated to their permanent location on Sylvan Ave. The culvert at Sylvan Ave. was subsequently completed during the summer of 2005.

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