The bridge was closed to motorists in April 2019 after faults were found in the cast iron casing.
Now the 133-year-old bridge has also been closed to pedestrians and cyclists following ongoing monitoring by specialist engineers.
Cllr Stephen Cowan, Leader of the London Borough of Hammersmith & Fulham, said: “Safety is the number one priority.
“I’m absolutely sure that we averted a catastrophe by closing this 19th century suspension bridge to motor vehicles last year.
“We have some of the best engineers in the world working on this scheme. They advise we now face a similar dilemma.
“I appreciate how inconvenient this will be to thousands of people on both sides of the river and I am sorry about that, but we must follow the engineers’ advice which is why the bridge will be closed with immediate effect.
“We will update everyone as soon as engineers have investigated the scale of the recent damage. I have instructed them to find a plan to safely reopen it as quickly as they can.”
Hammersmith Bridge and the heat
Hammersmith Bridge is a cast iron structure designed and built by Sir Joseph Bazalgette.
Cllr Cowan said: “The micro-fractures were only discovered because in 2014, I commissioned a comprehensive structural integrity review of all aspects of the bridge’s suspension structure which began in 2015. That was the first such review in decades.
“The bridge had been badly maintained for many years. The structural integrity review quickly began to find decades of unchecked corrosion riddled throughout.
“It found that important mechanisms on the bridge had seized up years earlier causing the suspension structure to cease to operate as it had been designed to – causing other problems elsewhere in the machinery.
“Last year, using the latest technology, it discovered dangerous micro-fractures in the cast iron pedestals that hold the suspension structure in place.”
“These unchecked structural failures compromised the flexibility of the suspension chains over previous years and caused the micro fractures.”
During the recent heatwave contractors have done everything they can to reduce the temperature of the bridge – including hosing down the bridge pedestals and chains with cold water.
Specifically, the suspension chains are affected by extreme temperature changes. This past weekend when we experienced heat above 30 degrees, engineers worked around the clock to cool the chains and the foundation pedestals to prevent the bridge from failing.