The Messeturm in Frankfurt am Main was completed in 1991 and is the second-tallest building in Germany. The lobby at ground floor level has been revamped to a design by architect Helmut Jahn working with Matteo Thun & Partners. The work involved both aesthetic and energy efficiency upgrades. Engineers from the Werner Sobek practice cooperated in the design of the façade with its 17m high insulating glass units. Unique to this project are the panes of insulating glass bent to a radius of 24m. Flat panes arranged in polygonal form was ruled out, which meant that every pane had to be bent with a certain curvature.

seele’s team of designers, engineers, logistics specialists and erection crews developed the steel-and-glass elements in just seven months prior to work commencing on site. Doris Erdt, Senior Design Manager at seele GmbH. said,

“All our experience with oversize panes gained over the past 15 years was called upon for the Messeturm project. The result is a complete package involving the design, logistics and erection for these 17m high panes in the heart of the city – all from one supplier.”

Bent insulating glass units
The special feature of this design is that the façade essentially consists of only a few parts: just nine panes and ten posts on each side of the tower. There are no horizontal members interrupting the glass, which helps to create lightness and transparency despite the dimensions. Owing to the huge size, each pane requires special bearings and must be held in place with glazing bars. The cold-bent insulating glass units measure approx. 17 x 2.8m, are approx. 71mm thick overall and are supported by stainless steel posts weighing approx. 3.5t each. With its solar-control coating on level 4 to reduce solar heat gains, the insulating glass therefore combines aesthetic and functional criteria.

Slender stainless steel posts
Another feature of the design are the 17m high slender stainless steel posts that hold the insulating glass units (each weighing approx. 6t) in position. Each post is fabricated from three parts that are factory-welded seamlessly together to form a post that is not only trapezoidal in section, but also tapers towards the top and base. This shape ensures a particularly elegant appearance. But they also loadbearing. That is a real challenge during handling in production and on site. To transport the posts to the site without any problems, seele designed a special cradle for the HGVs and a lifting apparatus so that the slender posts could be positioned without deforming.

Challenging logistics and erection concept
The tight schedule, city-centre location and cramped site conditions called for a perfectly coordinated logistics and erection concept from seele. Specially adapted inloader frames were used to transport the 17m high panes safely. On site, the extra-long HGVs had to be manoeuvred with millimetre accuracy as the space available was very limited. Great care was also needed when operating the special glass lifting apparatus with its 90 or so suction cups for lifting the approx. 6t panes off the trucks and into position.

Dirk Herrmann, Head of Erection at seele GmbH explains,

“Everything had to work well together in this erection concept – people, equipment and nature. We plan every detail very precisely in advance and take account of all aspects that affect erection; wind, temperature and humidity are all crucial aspects during construction work. With its many years of experience on sites all around the world, from San Francisco to Sydney, seele’s well-rehearsed team is aware of the challenges.”