In the heart of the city of Frankfurt, the visionary skyscraper project “FOUR” is rising higher and higher with each passing day. This is being made possible by Liebherr’s state-of-the-art luffing jib cranes, including the world's first to feature pioneering fibre rope technology. Liebherr and its partner Nagel Baumaschinen are working hand in hand with project developer Groß & Partner to bring the vision to life.

Situated along the Main River, Frankfurt’s impressive high-rise panorama has led to the city being dubbed as “Mainhatten”. The skyline is already dominated by an array of skyscrapers and now four more towers, ranging from 100 to 233 metres in height, are set to join them. “FOUR” impresses with its future-oriented architecture and sustainable urban development concept. The site in question is located in the banking district, right next to the Commerzbank Tower; the tallest skyscraper in the European Union.

But the project is about much more than just building more high-rises. “Our approach is what I like to call clockwise planning. We ask ourselves how people live their day: when do they get up, what routes do they take, what infrastructure do they use, where do they spend their time? This helps us determine which spaces we need to create so that people feel comfortable in the FOUR,” says architect Ben van Berkel.

He and his team from UNStudio were faced with the challenge of reconnecting and revitalising an area that had been cut off from urban life for decades. Led by the maxim “Live the city”, they aim to achieve this with a concept that offers something for everyone: offices, apartments, restaurants, cafés, hotels, public spaces and new connections to the city centre will be created on the site. “FOUR” thus breaks with single-use thinking and caters for a variety of purposes.

The use of a 258 HC-L 10/18 Fibre marks a world first. “FOUR” is the first construction site ever to have a Liebherr luffing jib crane with fibre rope. Fibre cranes achieve significantly higher performance values compared to their steel rope counterparts. In general, HC-L cranes specialise in high hook heights, and the advantages of the lighter rope are particularly evident at such heights.

Fibre rope is more durable, easier to handle when reeving due to its lighter weight, and maintenance is less complicated as lubrication isn’t required. And on top of all that, operational safety is also increased; crane operators are able to see at a glance when the fibre rope needs replacing due to wear or damage. The components of the rope’s cover wear out at different rates – when the red coated core becomes visible, it’s a sign that the rope has reached the end of its service life.

Hardly a month goes by without at least two cranes increasing their hook height further. The tallest crane is working at a tower height of 243 metres, the lowest climbed crane at 132 metres. The luffing jib cranes climb on the inside and outside of buildings. This concept, which has also been developed by Tower Crane Solutions, has a number of advantages. The outside-climbing cranes can dismantle the inside-climbing cranes at the end. So no additional lifting equipment is required. The cranes climbing externally on the building climb down independently to a minimum structure height and can then be finally dismantled cost-efficiently with a mobile crane.

The concept also requires fewer tower sections than if all cranes were to climb on the outside. This saves costs and CO2 emissions that would have resulted from the delivery of additionally needed tower sections. Experienced service technicians from Nagel Baumaschinen and Liebherr carry out the climbing stages to ensure a safe process and as little downtime as possible for the crane concerned. As of the end of April, 40 climbing stages have already been successfully completed.

Senior site manager Roger Schmitt from GP Con GmbH, a subsidiary of Groß & Partner, says, “Our collaboration with Liebherr has been characterised by great motivation, technical expertise and teamwork ever since we started construction work on the FOUR. (…) With nine cranes on a relatively small, inner-city construction site, coordination, simultaneous operation, and the sometimes weekly new climbing phases of these cranes have been, and continue to be, a huge challenge. It can only be done with exceptional preparation, joint planning, and punctual implementation. With Liebherr and Nagel Baumaschinen, we have reliable and competent partners at our side who contribute to the positive progression of this project through their own initiative and good ideas.”

Project Website Groß & Partner