The project was so big air traffic controllers at Perth Airport had to be involved.
It was the first significant lift in building the centrepiece of the $1 billion WA Gateway project - the three-tiered interchange at Leach and Tonkin highways.
Starting late last week, a 46m crane was used to swing 24 beams into place - each 24m long and weighing up to 100 tonnes - for the first of four interchange bridges.
The lift is expected to finish today.
Once the beams are in place, more than 1000cum of concrete will be poured for the bridge surface.
Given the project's proximity to Perth Airport, a special breach permit was needed for the beam lift because of aviation height restrictions.
A project spokeswoman said the beams lift was carried out in close co-ordination with air traffic controllers.
Gateway WA is the State's biggest and most expensive road project.
The Leach-Tonkin interchange will be 13.9m from its lowest to highest point.
It is expected to be finished in early 2016.