membrane structure, Structure with a thin, flexible surface (membrane) that carries loads primarily through tensile stresses. There are two main types: tent structures and pneumatic structures. The Denver International Airport (1995) features a terminal building roofed by a white membrane stretched from steel masts. Another such structure is London’s The O2 (formerly Millennium Dome), which has a tensioned membrane structure with a diameter of 320 metres (1,050 feet), one of the largest in the world.