The Structural Design of the New Techo International Airport in Phnom Penh, Cambodia

The paper describes the structural design of a new greenfield international airport in the capital city of Cambodia, Phnom Penh. The main passenger terminal building features a 360 m × 216 m (1,181 ft × 709 ft) structural steel roof. To minimize seismic demand and optimize its dynamic response, the roof is structurally independent from the post-tensioned concrete structure below. The roof comprises a series of shallow dome-shaped, single-layer steel gridshells, spanning 32 m (105 ft) each way onto a square grid of trussed moment frames with trussed columns. By mobilizing in-plane shell action through geometry, the gridshells achieve a high clear span-to-member depth ratio. The depth of the tri-chord roof trusses varies from a minimum at midspan to a maximum at the column head where the bottom chords curve downwards to merge with the trussed column chords. Member design of the roof was carried out in accordance with the Direct Analysis Method of AISC 360. Beneath the roof, the 288 m long × 180 m (945 ft × 591 ft) wide concrete superstructure was designed and constructed as a single structure without intermediate expansion joints despite its large plan dimensions. The superstructure comprises post-tensioned band beams, spanning 18 m (59 ft) in each direction, which were detailed as intermediate moment frames to ACI 318. The project also includes a pier building, 875 m (2,871 ft) long.