The skeleton of the city's tallest building, One Liberty Place, is steadily climbing skyward as structural steel work has reached the 58th floor. Construction is to be topped out above the 60th floor early next month. In September, the structure broke a cherished Philadelphia tradition when work on the 44th floor put it above the top of the William Penn statue on the 547-foot City Hall tower. One Liberty Place is to reach 947 feet. About 450 construction workers are on the job, including ironworkers, concrete-decking teams, elevator installers, carpenters and teams installing granite and glass curtain walls. The Rouse & Associates project is at 17th and Market Streets.