Three new developers are joining the city of Quincy’s efforts to reshape its downtown, unveiling plans for a pair of multifamily projects and a 116-room hotel.

Quincy developer Peter O’Connell proposes a 15-story, 122-unit luxury residential project to be built in the city-owned Hancock parking lot in the heart of downtown. To go forward, O’Connell needs to negotiate a land agreement with Quincy Mayor Thomas Koch, subject to city council approval.

Sean Galvin of Quincy-based Galvcon Development plans 48 condominiums at the corner of Hancock and Cliveden streets.

LBC Boston, headed by developer Alex Matov, plans to build a 116-room hotel at 1500 Hancock St.

The combined cost of the projects is $100 million, Koch announced at a press conference Tuesday.

The city also is seeking proposals from developers for a parking garage to be built on part of the Hancock lot, with other portions of the property made available for development at a later date.

In November, Boston-based Gate Residential announced plans to build a six-story building containing 169 residential units and 12,000 square feet of retail called West of Chestnut. That project – estimated for summer 2016 completion – will be built on land owned by Quincy Mutual Group. A second phase would include 220 housing units and additional commercial space.

The previous master developer, White Plains, N.Y.-based Street-Works, was removed by Koch in March 2014 after missing a series of deadlines in agreements with the city.

Since then, the city has sought individual developers for various phases of the project, which was originally valued at $1.6 billion.