Leibniz Universität Hannover

In compliance with the rules, the roof structures of sports halls that are suitable for competition also have to span the stands, in addition to the sports field, without support. [52] Due to the large span of more than 28 meters, roof trusses in steel, wood or prestressed concrete constructions can fulfill this requirement, which must also be fire-resistant according to the Lower Saxony Assemblies Ordinance [47]. It is the purpose of this work, to optimize roof trusses in steel or hybrid steel-wood construction in terms of static, construction and fire protection as well as economic aspects. While the dimensioning can be carried out successfully in the limit of the load carrying capacity of a steel truss, an implementation of the fire resistance duration of 30 minutes under the assumption of the uniform temperature time curve (UTTC) is only possible by using uneconomically oversized profile dimensions on the component plane. If the restraining forces as a result of thermal expansion are applied, a proof for the entire support structure is not possible. Especially in sports halls that have a low fire load density when properly used, natural fire models can be used to show that the expected gas and steel temperatures are significantly below those under approach of the UTTC. In case of fire, a dimensioning of the steel truss is achieved with the simplified natural fire model local fire as well as with a general natural fire model with thermodynamic calculation in FDS. [29] The successful dimensioning of a steel truss protected by an insulating layer-forming fire protection system was proved in a variety-study. In addition, a hybrid steel-wood construction is dimensioned, consisting on the upper side of a laminated timber beam curved in the ridge area and on the lower side of a steel rod. Due to the good thermal behavior of wood in the event of a fire – the pyrolysis of wood forms a protective carbon coating – the fire safety proofs of the wooden components are also possible through appropriate dimensioning. In order to be able to utilize this protective effect of wood on steel parts, experimental fire tests and numerical simulations have been carried out on steel cross-sections protected with wooden sleeves. Already a few centimeters of wood layer thickness are sufficient to keep the steel temperature well below the critical range.