Friedrich Sponsel Hall

• Projekt
  Friedrich-Sponsel-Sporthalle

• Architekt
  Planung: IBG - Ingenieurbüro für Bauwesen Markus Gräßel
  Statik: IB Trafektum GbR

• Bauherr
  Stadt Erlangen, Amt für Gebäudemanagement

• Produkt
  1.100 m² Element-Dach mit Domitec® RAL 9007
  333 m² GBS®-Dach

• Verarbeiter
  Hoffmann GmbH

• Fotos
  IBG - Gräßel OBJEKTPLANUNG

Ein Dach für das Dach

The Friedrich Sponsel Triple Hall with a total usable area of around 940 m² was built in 1971 in the center of Erlangen. The aging building is intensively used by various clubs and schools for sports events and training, for example by the field hockey department of TB Erlangen. During the inspection of the hall roof, the static verification of the HP prestressed concrete shells revealed that under special, exceptional weather events, the verification could no longer be carried out without restrictions: The water-bearing levels consist of 33 semicircular “concrete troughs” about 13 meters long and sealed with bituminous sheets. Wire glazing in the steeply inclined sheds provided daylight. The free-spanning, so-called HP shells are statically supported on 30-meter-long prestressed concrete trusses and the exterior walls. The precipitation water in each of these half-shells is drained at its ends via flat-roof drains into trailing pipes laid under the ceiling inside the hall, from where it is fed to the receiving watercourse via downpipes.

Distributing or redistributing / diverting loads
Today, high loads on the roof structure are caused by the greater number of heavy rainfall events and, in winter, possibly by steadily increasing snow loads. This also became a problem for the sports hall, as the existing drainage system could not guarantee backwater-proof drainage of the precipitation water during such heavy rainfall events and thus temporarily high static loads could not be excluded. The idea of installing additional downpipes to relieve the load was rejected, as the necessary core drilling would have weakened the structure of the prestressed concrete half-shells to an unacceptable extent.
Until a solution was found, the city had a permanently monitored special measuring device installed on the roof of the hall to record the amount of precipitation for safety reasons. It was used to determine the maximum permissible amount of heavy rain at which a restriction of use or closure of the hall would become necessary.

In the medium term, however, a permanent, independently functioning solution was sought. Ultimately, the city decided to implement a lightweight roof system that would ensure the continued operation of the Friedrich Sponsel Sports Hall for about ten years until a new sports hall building could be considered. Since the existing hall roof was no longer allowed to bear any additional loads according to the static evaluation, a very shallowly pitched monopitch roof structure was chosen, which is supported only by the exterior walls. The cladding at the ridge and eaves was to be vertical wall cladding, while the side connections were to be steeply pitched hipped roofs for clearance reasons.

Short construction time, fast utilization
The search was on for a special cantilever roof structure capable of spanning a hall length of almost 31 meters. Not only did it have to meet the structural requirements, but it also had to allow for a short construction period to ensure trouble-free operation of the hall. The choice fell in favor of the DOMICO Element roof. With maximum prefabrication and time-saving assembly, the compact lightweight element meets the highest requirements in terms of cost-effectiveness, thermal insulation and weather protection. The DOMICO Element roof consists of load-bearing profiles, cassettes, mineral thermal insulation and retaining profiles, and is manufactured in the factory with all the required openings. In addition, a vapor-diffusion-open cover sheet not only protects the construction during transport, but also enables weather-independent installation. Thanks to the specially developed sub-span technology, spans of up to 33 m can be freely bridged – perfect for use on the Friedrich Sponsel Hall.

Assembly by mobile crane
To install and support the under-spanned element roof, a steel construction frame for the 31 x 41 meter hall with a roof pitch of 1.5 degrees first had to be manufactured and fixed to the outer walls. Due to the different roof movements and deflections, the supporting frame is structurally completely separated from the existing roof. Aluminum maintenance paths were attached to the prestressed concrete trusses running parallel to the roof elements, and the exposure sheds were protected with a robust, three-layer sarking membrane. The logistical challenge was the delivery of the 31-meter-long roof elements due to the cramped inner-city location. Due to the perfect preparation at the construction site and the high degree of production at the factory, the roof elements could be installed in just one day with the help of a mobile crane. As the holders for the weather protection level made of Domitec roof profiles were also pre-assembled at the factory, a lot of valuable time was also saved when laying the profile sheets on site. The roof profiles are designed ex works with a ridge elevation as well as an eave chamfer. On the one hand, this ensures safety against backwater and optimum rigidity at the ends of the profiles, and on the other hand it prevents water from being driven in. Water drains off via the protected eaves edge and not via the cut edges. The applied longitudinal joint seal ensures increased rain resistance even in extreme weather situations.

Rain without backwater
The smaller hipped roof surfaces and vertical eaves flashings were clad with DOMICO GBS profiles on cassettes as a deck carpet pad. Drainage of the new attached hall roof now takes place at the eaves and the two hipped roof surfaces into exterior, pre-hung gutters. The emergency overflow can drain off into the open via the front edge of the gutter, so that the rainwater is now discharged from the building without backwater or damage. The non-penetrating, quick and uncomplicated installation results in time and cost savings. Photovoltaic systems can also be fastened without penetration at any time.