As a result of the findings the concrete structures are to be demolished after design and construction flaws were discovered.
The structures consist of two separate roads linking Lime Street to Dale Street (south flyover) and Tithebarn Street (north flyover), running directly behind the city's museums and galleries in William Brown Street.
They were closed in the 1980s for repairs and further remedial works were carried out in 2005 and 2013 as part on a regular maintenance regime.
Following new legislation on major highways structures, a Post Tensioned Special Inspection (PTSI) began in 2016 to assess the northern and southern sections, both of which are more than 240 metres in length.
This found problems with drainage, internal support, barriers and bearings which led to the flyovers being shut last autumn for investigations into potential hidden defects and potential overstress.
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Since then, structural testing has been carried out, involving removal of the road surface, drilling into the decks and underground assessments of every supporting column has been carried out.
Engineers found the quality of construction using concrete and steel was poor, with tendons and ducts corroded and signs of structural distress including cracking over some supports.
They have calculated that strengthening the structures is not feasible and the cost of replacing them would be between £50 and £60 million, compared to a demolition price of £5.7 million.
Work is expected to start on taking them down in the summer, and in the meantime the council will be developing proposals to improve the Queensway Tunnel roundabout and the Hunter Street interchange at an estimated cost of £10 million to cope with increased traffic flow caused by the loss of the flyovers.
The footbridges across Hunter Street will be fitted with temporary ramps to allow pedestrians to cross the road and minimise the impact on traffic flow.
Councillor James Noakes, Liverpool City Council’s Cabinet Member for Highways, said: "The Churchill Way flyovers are a relic of a plan from half a century ago that was never completed.
"Public safety is absolutely paramount and despite the obvious inconvenience the demolition will cause, we can’t compromise on safety and it is simply not economically viable to make them safe.
"Although there has been an increase in traffic at peak times in and around the Queensway Tunnel as a result of the closure, the city has been able to cope with it.
"What we will now be doing is working up detailed designs for junction improvements which will help deal with the removal of the flyovers.
"Our analysis shows that it helps support our City Centre Connectivity Scheme and particularly makes it easier for vehicles to exit the proposed new bus hub.
"We will be working hard to keep all of our city centre stakeholders and the public informed at every step of the way."
(CD/MH)
