PITTSBURGH — Traffic is expected to be detoured for months after three bridges closed today for rehabilitation projects. The closures involve the Ambridge-Aliquippa Bridge in Beaver County, the South Highland Avenue Bridge in Pittsburgh’s Shadyside neighborhood and the Levi Bird Duff Bridge — which connects Ross Township and Bellevue. The $23.6 million project to rehabilitate the Ambridge-Aliquippa Bridge is expected to take until around Thanksgiving, the $2.9 million replacement of the South Highland Avenue Bridge until mid-September, and the $3 million repairs on the Levi Bird Duff Bridge until November.