The Fremantle Traffic Bridge will reopen again on Tuesday morning after it was closed last week because of repairs.
The bridge was closed on Friday after erosion was found on the foundation of one of four piers by inspectors who were working on strengthening it.
Main Roads said underwater divers worked all weekend bracing the bridge piles with steel ties to add strength and prevent any sideways movement below the water.
"The work is enabling us to complete the necessary stabilisation works in order to re-open the bridge to road users," Main Roads said on its website.
"Over the coming weeks, there will also be strengthening works carried out on all four piers."
Labor MP Simone McGurk was critical of the Barnett government for failing to replace the 77-year-old bridge, despite multiple reports of its deterioration.
"When Labor was in government we had set aside $80 million towards the cost of a new bridge. But in 2011 the Barnett government removed that money and decided to put in place a series of running repairs instead," she said.
"The traffic bridge was never designed to last this long and it was never designed to carry the weight of traffic that it does today."
The bridge, which was built in 1939, normally carries 30,000 cars a day.
