a metal deck. They are designed to carry live loads of , as well as partitions weighing up to . The Times stories contain a raised floor structural system, with the finished office floors being above the floor slabs. Conversely, on the upper stories, the finished office floors are the slabs themselves. The superstructure of the tower is braced to the mechanical core, which measures . This allows the perimeter of the tower stories to be no more than from the core. The lower section of the tower, containing the Times offices, contains two sets of bracing frames that surround the core from north to south. The top 21 stories contain a single bracing line extends from north to south. There are outriggers at the mechanical floors on the 28th and 51st stories. "X"-shaped braces are used at the tower's corners because the elevator core limits the extent to which west-east bracing lines could be used. The "X"-braces were pre-tensioned during construction to compensate for the shortening of columns. The braces are built in pairs, rather than as single rods, which would have required larger diameters. On the north and south elevations, the center bays are cantilevered about past the perimeter columns. The floor girders of the cantilevered sections are arranged into three framing lines: two at the outer ends of the cantilevers and one at the center. The central girder on each floor is supported by a Vierendeel truss. The outer girders are connected to the perimeter columns by diagonal beams and to each other by columns. Because the Times stories have raised floors, the girders on these stories protrude through the facade in an offset "dogleg". The 51st-story mechanical space contains elevator rooms, air-conditioning, lighting, and telecommunications equipment, as well as a control area for the building's mechanical services. The main roof above the 52nd story consists of an asphalt covering, above which are concrete pavers on stone ballast. The steel mast atop the building is about tall and is made of carbon fiber, allowing it to bend during heavy winds without snapping. It extends from a circular baseplate on the 51st story, where it measures wide, and tapers to a width of at its pinnacle. The mast is also supported from the roof of the 52nd story. To support the mast, trusses were designed within the floor slabs on the 51st and 52nd stories, and vertical trusses