Cooper Trading Inc., a construction materials supplier in Irwin, Pa., since its founding in 1992, is expanding into the South Side of Pittsburgh. "We are getting ready to open (our new location) there," said Pete Cooper, the company's president and founder. "Probably the middle of next month, (we will be) up in running." The company, which currently has a 5,000-square-foot corporate office and 14,000-square-foot warehouse in North Huntingdon, will set up shop at 1001 Muriel St., on the south side of the 10th Street bridge.