Wolff cranes for mixed-use development construction

The new Kaiserquartier (translates to Imperial Quarters), being built on behalf of Eric Schmidt Kaiserquartier, covers an area of 15,600sqm. It will comprise 130 apartments of different types (from student accomodation to luxury penthouses); commercial spaces for offices, stores and medical practices; and an underground car park.

Freundlieb is building the new development largely with prefab components. All balconies, loggias, and staircases are prefabricated and have to be lifted into place in one piece, with the heaviest element weighing roughly 10t.

In order to cover the whole site, the company decided to use three cranes with tip load capacities of five to six tonnes at 50m to 60m. A 315tm Wolff 7532.16 Cross hammerhead and two 250tm Wolff 7032.12 Clear flat tops were chosen.

Given the size of the construction site and the excavated depth of around 4m, the assembly of the cranes from the surrounding streets would have been inefficient. Therefore, a 30m-long ramp was raised inside the pit over which the mobile crane and trucks could safely access the designated assembly locations. Two of the Wolff cranes were erected on foundation anchors in the floor of the underground car park and one on a cross frame outside the construction pit.

Even the dismantling of the cranes had to be carefully planned in advance. “With nearly the entire building superstructure constructed on the underground car park, many of open spaces and courtyards will not have the necessary load-bearing capacity for a 300t mobile crane,” said Carsten Druske, head of rental operations in Germany and branch manager of Wolffkran Dortmund. “In addition, access will be limited by the new buildings, so that the crane parts will have to be lifted over them."

Wolffkran addressed the issue by planning places outside of the building complex from which the mobile crane can safely dismantle the Wolff cranes. “Furthermore, the construction site’s slope also needed to be considered during the planning process in addition to the various building heights throughout the individual construction phases,” Druske explained.