VICKSBURG — Cranes for a salvage company work to refloat a grain barge that sank Thursday after striking the old U.S. 8- bridge. The company was expected to refloat the barge Saturday, but U.S. Coast Guard Petty Officer 1st Class Matthew Schmidt with the Coast Guard’s Sector Lower Mississippi in Memphis, Tennessee, said a problem with one of the cranes forced work to stop. He said the company would resume efforts Sunday to bring the barge up.