A delicate operation to replace a 109-year-old bridge in Subiaco is under way.

One of the biggest cranes in WA had to be brought in to rejoin Hamilton Street and reconnect Subiaco and West Leederville in a massive task that had to be completed within 24 hours.

The complex project involved the installation of five concrete bridge beams over the railway line, weighing 58 tonnes each.

The cranes brought down from Port Hedland made light work of it, taking only 15 minutes for each beam to be installed.

The 109-year-old timber bridge that joined the suburbs was demolished in February as it was past its use-by date.

It is the second of four timber bridges being replaced by Main Roads along the Fremantle train line.

“The Ashton Avenue bridge was done in last year in September, and the fourth one is the Eric Street Bridge which is the oldest of the four and carrying a lot of traffic,” Main Roads director of metropolitan operations Peter Sewell said.

The entire Fremantle line had to close for the beams to go in so there was only a 24-hour window to complete the project.

Meeting the deadline was particularly important given thousands of Dockers fans will use the train service to get to Optus Stadium tomorrow.

The two-lane bridge will include two wide pedestrian walkways on each side.

While 2800 cars used to go over the old bridge, this number is expected to go up when a new high school opens around the corner.

The $8 million bridge is expected to be open to cars by September.