One person is hurt escaping a weekend residential fire in Janesville.  Firefighters responded to a burning duplex in the 2900 block of Black Bridge Road about 2:30 p.m. Sunday.  The first to arrive say flames were showing from the garage door, and fire was extending into the attic of both units.  Two occupants, two dogs, and a cat escaped the structure, but one occupant suffered minor injuries.  All occupants are displaced.  Damage is estimated at $141,600 for the structure and $41,400 for the contents.  The cause is under investigation.