In der südkoreanischen Metropole entstand in den Jahren 2007 bis 2011 das Busan Cinema Center (BCC), das ab 2012 Schauplatz für das Busan International Film Festival (BIFF) sein wird, eines der wichtigsten Filmfestspiele in Asien. Zwischen einem Kinokomplex in Massivbauweise mit mehreren Kinosälen und einem großen Theatersaal sowie einem Verwaltungsbau spannen zwei Stahldächer mit gewaltigen Ausmaßen, welche die Open‐Air Bereiche des BCC überspannen und dem Projekt ihre charakteristische Signatur verleihen. Während das so genannte small roof zwischen den Gebäuden ca. 110 m weit gespannt ist, kragt das big roof an einer Seite spektakuläre 85 m aus und ist somit die weiteste Dach‐Auskragung der Welt. The roofs of the Busan Cinema Center. The Busan Cinema Center (BCC) has been built between 2007 and 2011 in the Southkorean metropolis Busan. The BCC will be the future location for the Busan International Film Festival (BIFF), which is one of the most important film festivals in Asia. Two roofs with immense dimensions are spanning between a massive building comprising several cinemas and a big theatre and between a building for administrational use. The two roofs are protecting the open air areas of the BCC and are the characteristic elements of the architectural design. The so‐called small roof is a single spanning roof with a span width of app. 110 m. The big roof is a spectacular canopy cantilevering 85 m. It is the longest cantilevering roof structure in the world.

and the outdoor theater comprising 4300 seats. A roof spanning the cinemountain and the BIFF Hill acts as an element of weather protection, providing shelter to the outdoor amphitheater from the sun and rain. The red carpet area in front of the cinemountain is protected by an 85 m cantilever structure. This big roof structure covers a total area of 165 × 62 m 2 including a three-storey restaurant in the back span. Structural System of the 85 m Cantilever Roof Conceptual DesignThe dynamic form of the big roof and the light emitting diode (LED) surface of the outdoor canopy soffits provide the Busan Cinema Centre with its symbolic and representative iconographic feature. The upper part of the roof is composed of a flat surface with a circular opening, where the double cone intersects (Fig. 2). The lower part is a three-dimensional (3D) undulating surface. The big roof is 32 m high above the ground level. The roof structure cantilevers 85 m from the double cone with a back span of 45 m. At the back span, tension elements are used to hold down the roof. The depth of the roof varies between 3,5 m at the tip and 22 m in the back span area. Within the back span, there is a three-storey restaurant. The roof is clad with lightweight metal sheeting. Owing to high dead load deflections, all members were constructed pre-cambered. The spiral ramp is connected to the underside of the roof with tension rods. The double cone is a hyperbolic steel structure with penetrations to allow for access. It acts as the clamped support for the cantilever roof. The lower part of the double cone is made of concrete, which corresponds to the form of the back span. Structural System Cantilever RoofThe roof is composed of an orthogonal steel truss girder system with longitudinal and transverse trusses. The girder grid spans 5 m at centres in both directions. The intersection between the main chords of the truss is assumed rigid, giving them stability and allowing a load-bearing behaviour in both directions. This is very important because of the sensitive aeroelastic behaviour of the 85 m cantilever. The chord members are made of welded rectangular hollow sections. The member sizes vary between 200 × 200 mm 2 and 700 mm × 400 m. AbstractThis paper discusses the design and construction processes of the 85 m cantilever roof of Busan Cinema Centre. It introduces the project with a brief description and focuses on the structural challenges faced by the engineers during the design and construction phases while resolving issues regarding the cantilever. As the 85 m cantilever with the demanding architectural geometry is a nonconventional structure, the design challenges faced were to establish sensible loads for the structure and to find a reasonable workflow to deal, exchange, and analyse the desired geometry in cooperation with the design architects.