News Review
PND Awarded SR-520 Floating Bridge Mock-up Contract
The Washington State Department of Transportation elected to construct a 120-foot-long, full-size pontoon test mock-up prior to the construction of the new SR 520 floating bridge pontoons. The intent of the mock-up was to optimize the geometry of the pontoons to simply forming and casting for the new SR 520 Bridge while preserving an intended 85-year design life.
The optimization included evaluating new concrete mix designs, “place and vibrate” methods for effectiveness in consolidation of the mix design, and measuring form pressures for various concrete placing rates in the tall thin exterior walls. An equally important objective was to assess and develop methods to mitigate structural cracks resulting from thermal stresses induced between curing concrete of different ages and maturity.
Special Conditions: - Unusual form geometries associated with post-tensioned connections and unique pontoon details
- High concrete form pressures associated with tall, thin forms and rapid rates of concrete placement
- Providing a complete form and falsework package as part of the publically advertised plan set