Drafts by Bögl Gierer Architects from Munich

The steel substructures were developed and implemented by Max Bögl Stahl- und Anlagenbau according to designs by Bögl Gierer Architekten from Munich. The glass roof construction spans an area of approx. 3,100 m². It consists of three identical pent roofs arranged around a pentagonal concrete core. The pane panels of the roof construction are supported by a hollow steel profile construction with linear bearings. The design of the glass roof placed high architectural and engineering demands on all those involved in the planning. In the following some parameters are summarized, which had to be considered during the planning.

Complex planning details

In order to structure the appearance of the supporting structure without sacrificing the lightness of the steel substructure, the frame ledgers were designed as understressed fishbelly beams. Deformations of the supporting structure due to loads and temperature changes had to be coordinated with regard to compatibility with the glass panes and the jointing. Component thicknesses and pane dimensions had to be varied until the corresponding compatibility could be proven. The building physics behaviour in the shopping mall under the large glass surface was determined by climate simulation calculations. The use of specially coated glass panes ensures a comfortable indoor climate in the building even in the case of intense sunlight. The air conditioning is supported by electrically opening double flaps in the roof surface, which allow natural ventilation below the glass level. The supporting elements of the glass covering were designed as slender understressed fish belly beams whose height adapts to the stress curve. In addition, careful stability tests were carried out to ensure that the filigree profiles would not tilt under load. The glass roof can be walked on for cleaning purposes. This requires appropriately dimensioned glass panes and safety devices for the cleaning personnel. In order to be able to install advertising installations below the glass roof and at the same time enable the cleaning of the glass surfaces from the inside, an access system was integrated into the steel construction.

Design and dimensioning of the steel structure

In the pre-planning phase, various structural variants were designed and pre-dimensioned. It was "played" with profile cross-sections, tensioning and under tensioning, the feasibility of all functional aspects was checked and the appearance coordinated with the architect. From this, the final supporting structures were developed, consisting of the main frame with underspanned frame beams and longitudinal purlins in rectangular hollow profile construction. The execution planning for the steel construction was carried out entirely in Tekla Structures. 2D plans were created and NC data derived for the connected plant's own steel production. A total of 160 tons of steel were used, which had to be coordinated in further models by different planners.

Production of the steel construction

In order to meet the high tolerance requirements of the glass construction, the steel frames were assembled in specially designed and manufactured templates. The top rails were already welded on during production for later fixing of the glass panes. After the final coating of the steel components, they were still available on the factory premises of the company commissioned with the glass construction assembly for pulling in the sealing systems.

Installation of the roof

In November 2014 the construction of the roof could be started. For this purpose, the frame elements assembled into large components in the steel construction production at the Sengenthal plant were delivered at night by special transport to the nearby construction site and lifted into their final position by the building construction crane. After assembly of the steel structure, a safety net was stretched under the steel structure so that the installation of the glass panes could begin immediately afterwards. The manufacture, assembly and alignment of the steel structure was carried out with great care. Local adjustment work on the glass supports was therefore not necessary, and the flatness of the panes and the overall surfaces was always guaranteed. Due to adverse weather conditions, however, the jointing could not be completed until spring 2015. With the new city quarter "NeuerMarkt", the largest connected shopping mile of the southern Upper Palatinate with a length of almost one kilometre was created. The visitor magnet of retail and gastronomy is complemented by a modern multiplex cinema, a 4-star hotel as well as office, practice and service areas including an underground car park with 550 parking spaces. Investor and owner of the 100 million Euro project is the Max Bögl group.