115 The regional indoor stadium of Liévin (France) hosts top level sport events and concerts. Every year international competitions, such as the “Meeting Gaz de France”, take place in the stadium. The project presented here, which is the roof of the stadium, is a part of the project of the renovation and the extension of the stadium and the CRAF (Centre Régional d’Accueil et de Formation) a regional centre for accommodation and education. The architects are Architecture Studio, Paris. The structure of the roof consists of half frames made of gluedlaminated timber supported by simple supports at their base and connected to each other by hinged connections at their top, thus spanning 66 m. These frames support secondary beams, which carry the roofing. In the scope of the renovations, the central part of the roof is demolished and replaced by a new structure on a higher level, while the structure of the concentric frames creating two semi cones at the two sides is to be conserved. In addition to the change of geometry, additional loads of stagecraft equipment are intended to be suspended on the roof structure, including the conserved part. The wish to conserve a part of the structure, in spite of these additional loads and the strict constraints of the architecture as to the dimensions of the new frames cross-sections, made the necessity of an accurate 3D finite elements model indispensable. The construction stages of the demolition and the reconstruction require a meticulous study. The concentric frames of the two semi cones at the two edges of the roof are equilibrated by the ridge beam under compression, passing between the centres of the semi cones. In order to demolish the central part, a solution had to be found in order to create two stable structures without the need of the ridge beam at that temporary phase. The method is to support the two centres of the semi cones and to cancel the compression by jacking these nodes. The objective of the calculation for this stage was to determine the force in the jack and the displacement required to cancel the compression in the ridge beam. The calculation has been done using three models. In the first, the two semi cones are modelled with the ridge beam. The load applied by the jack is acting at the centres of the semi cones while the roof is loaded by its self-weight. The force required at the jacks is that which yield a nil compression at the ridge beam. This force leads to a displacement of approximately 5 cm at the centres. In the second model, one half cone is represented with its support, where the ridge beam is removed. The loads here include snow and wind loads. The last model is the full model of the roof at the final stage with all of the loads and the particular load combinations of the stagecraft loads. The stagecraft is suspended on a complex of bridges hanged on the timber frames. In order to allow high loads and maximum flexibility to the organizers of the prospective events on the one hand and the use to the maximum of the cross-sections of the wooden members on the other, the maximum values of the stagecraft loads were defined for every frame and for every zone of the roof, rather than global limits for the loads. Thus, a certain point on a frame can be heavily loaded, provided that the total load on that frame and the total load in the zone in which that frame is located do not exceed the predefined limits. This method led to a complex system of load combinations which had to be introduced manually. Although symmetry has been considered with respect to the transversal axe of the roof, 33 ultimate limit state combinations are introduced. Further than the direct use of the results for the design of the roof structural elements, the realistic results for the support reactions, which include elevated horizontal reactions, were used for an economical design of the load bearing concrete elements and the foundations. The Roof Structure - Indoor Stadium The roof of the indoor stadium of Liévin (France) is a part of the project of the renovation and the extension of the whole stadium. The structure of the roof consists of half frames made of glued-laminated timber supporting the secondary beams, which carry the roofing and spanning (66 m). In the scope of the renovations, the central part of the roof is demolished and replaced by a new structure, which is on a higher level, while the structure of the concentric frames creating two half cones at the two sides is to be conserved. In addition to the change of geometry, additional loads of stagecraft equipment are intended to be suspended on the roof structure, including the conserved part. The ESA PT calculation model is performed for the three main construction stages: placing temporary supports using jacks, the demolition of the central part and the final phase of the complete roof structure. The Roof Structure of the Indoor Stadium in Liévin
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