MIAMI — The city of Miami Beach is ordering residents of a 164-unit condo tower to evacuate the building after engineers found significant damage to a critical structural beam in the parking garage. Miami Beach spokesperson Melissa Berthier said Thursday afternoon that the city planned to post an unsafe structure notice and order residents of the Port Royale Condominium at 6969 Collins Ave., to vacate immediately. Shortly before 5 p.m. Eastern time, the condo board sent residents a mandatory notice to vacate the premises by 7 p.m. In a letter Thursday to Miami Beach building official Ana Salgu…