In a statement Piano said it was a "great honour" to design the motorway bridge, which he did for free out of a sense of "civic spirit".
Renders show a minimalist white beam bridge supported at regular intervals by tall piers.
"It will be a beautiful bridge"
"It will be a beautiful bridge," said the architect. "A very Genoese bridge. Simple but not trivial. A steel bridge, safe and durable. Because bridges do not have to collapse."
Piano offered to build the new Morandi overpass in the aftermath of the bridge disaster, which killed 43 people.
Mayor Marco Bucci has requested that Piano supervise the construction of the €202 million (£182 million) project, which will be undertaken by a trio of Italian construction companies: Salini Impregilo, Fincantieri and Italferr.
Old bridge collapsed in August
The original motorway bridge, which was built in the 1960s, collapsed during a storm on 14 August 2018.
One of the reinforced concrete towers disintegrated, taking over 200 metres of the road down with it. Cars plunged over the edge and survivors were trapped in their vehicles under heavy rubble for hours.
Prior to the disaster the bridge had required near-constant repair work, prompting one concrete construction specialist to call it "a failure of engineering".
Italy had been experiencing many major infrastructure issues during a time of economic turmoil. The Morandi tragedy was the fifth bridge collapse in as many years.
Up to 20 people are being investigated by the Italian authorities on suspicion of involuntary manslaughter related to the disaster.
Piano set up his studio, Renzo Piano Building Works, in Genoa in the 1970s. The studio has just completed a new building for a university in Harlem, New York.