Let me explain
Kingdom Centre rises 302 m, and its top is spanned by a steel bridge 65 m long weighing about 300 tons, 300 m above the ground. Visitors enter it from floor 99, according to the centre's official website. It was designed by Ellerbe Becket with Omrania. The top is an inverted catenary arch spanned by the bridge. Omrania explains the tower works with two systems: the first 180 m are reinforced concrete columns and beams tied to a concrete core, carrying loads to a raft 4 m thick and 3,100 m2 in area. Above that is a steel structure, better suited to the complex shape created by the arched opening. What it means for engineers: the structural system follows the building's shape. Concrete for the regular part, steel where the form gets complex. What is the hardest challenge in installing a steel bridge 300 m up?