Accelerated bridge speeds construction completion

A $1.75 billion highway reconstruction project involving the creation of six bridge superstructures has been built in Utah, USA using the Accelerate Bridge Construction (ABC) methodology.

Accelerated Bridge Construction is faster than normal construction
Accelerated Bridge Construction is faster than normal construction

The 24-mile project south of Salt Lake City, Utah County, required complete reconstruction of the existing roadway and the addition of two new lanes in each direction. The existing pavement has outlived its useful life, and the new road needed to meet future traffic demand.

Provo River Constructors built 4 bridges to carry cross streets and 2 of mainline Interstate bridges. They did this by building each bridge superstructure in a precast area that was off the main roadway but near to its permanent location. Then equipment moved the entire bridge, from girders up through the deck and parapet walls, into its permanent position in one huge piece.

This is not the first time Utah Department of Transportation (UDOT) has used ABC. It had previously slashed an entire construction season from a project schedule by using this method.

Key advantages of the ABC method

The offline method offers 3 clear advantages:

  • Improved worker safety
  • Less disruption of traffic
  • Faster construction

Moving a superstructure

Accurate surveying is crucial when following the ABC approach. 'When we lay out the pier and abutments, we calculate their position in the office, and upload that onto our surveying equipment' says Dan Leslie, survey area manager for DEI Professional Services. 'Then we go into the field and lay out the corners of the abutments and wing walls, and for the centre bent we lay out the foundation corners and the centreline of the columns. The contractor grinds down the concrete on the abutments to the correct elevation. Once it's ground down, they're ready to move the bridge'.

For this Provo Centre Street bridge the prefabricating of the superstructure is at exactly the same elevation as it will be in its final permanent position. That eliminates the chance that somebody will neglect to calculate a change in elevation when converting the numbers from the superstructure to the abutments. The design surface is compared to the actual elevations of the tops of the girders and given to the carpenters to finally cut or fill in the concrete over the girders.

Jason Kack, a principal and survey division leader, says what satisfies him most about the Provo Centre Street Bridge is that it fits precisely into place. 'We had not done an ABC bridge prior to this bridge, so we learned the process,' says Kack. 'Our biggest challenge was to make sure that our quality controls were 100%, because if you move the bridge and it doesn't fit, it's a problem. So we're very pleased that the bridge fit and that we met the project schedule. And we're proud to be a part of the Provo River Constructors team.'

It took 2 trains each with 18 axles, to move the shorter span of the Provo Centre Street bridge in to place. Belgian contractor Sarens, working with Provo River Constructors, took just 1 hour and 28 minutes to guide the structure into place.

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