Continuing our nine-part Meet the Bridge Builders video series, this week’s episode reflects back on the effectiveness and time savings of the huge Movable Scaffolding Systems that helped construct the approach structures leading up to the main span. The Bridge Project was the first time that an MSS was used to construct a bridge in California.
Both MSSes were traveling steel structures that supported the formwork for constructing the roadway in 250-foot spans, and each weighed approximately 3.1 million pounds without a concrete load. With concrete, they weighed more than 6 million pounds each. When there was a stem and soffit pour, more than 50 crane operators, laborers and carpenters poured 700 cubic yards of concrete for that bridge span. More than 70 concrete trucks were involved in each pour.
The MSSes were used to construct each approach span at 80 to 180 feet above ground. They reduced overall construction time, compared to typical bridge projects that involve complex systems of wood beams, pipes and steel girders that rise from the ground, known as falsework. They also offer a safer, more efficient way to construct the roadways. As mentioned in the video, without the MSS, those falsework structures could take 6 to 8 months to build. The MSS could do it in 12 hours.
There were two MSSes: one orange, the other blue. The orange one was designed for construction on a straight road. The blue one was designed for a curved approach. The reason for the different colors? On community tours, the Communications team used to kid around that the designer was a Denver Broncos or Boise State fan. In reality, they were colored differently to enable the construction crews to properly assemble both separate machines.