At 555 m (1,820 ft) tall -- nearly twice as tall as the second tallest building in South Korea -- the 123-story Lotte World Tower is the country's first supertall building and the fifth tallest building in the world. The $2.5 billion tower and adjacent development, totaling 505,300-gsm (5.4 million-gsf), features a variety of usages, including office, retail, hotel, officetel (a combination office and apartment common in Korea), parking, museum and observation space.

Lotte World Tower's elegant tapered shape is a nod to traditional Korean art forms. Though the shape of the design led to challenging structural complexities, it was effective at minimizing wind loads. LERA worked closely with the architects to strike a balance between the structural efficiency gained by adding columns and the need to preserve open floor plans. Several structural designs were therefore studied: a system of concrete mega-columns with relatively small intermediate steel columns at the perimeter; a system of long-span spandrels with clear spans between concrete mega-columns; and a combination of the two.

The owner, Lotte, selected a system of long-span spandrels for the office and officetel floors, with spans of up to 24.5 m (80 ft) between mega-columns. At the building corners, the long-span spandrels cantilever 14 m (46 ft) beyond the mega-columns while bending to follow the building’s curved floors. These corners posed significant challenges for meeting the stringent deflection and vibration floor criteria.

The tower's primary lateral load and gravity systems consist of eight concrete mega-columns, concrete core walls and a series of outriggers and belt trusses located at the mechanical, refuge, sky lobby and hotel amenity floors. The belt trusses transfer the diagrid "lantern" structure to the column configuration of the hotel floors, as well as the columns of the hotel floors to the mega-columns at the officetel and office floors.

Click here to read an article published in Civil Engineering describing the tower's innovative structural system.