The man of numbers: Dr.-Ing. Christoph Diekmann and the statics of Red Heels

February 5, 2021

March 20, 2021 the sculpture RED HEELS by Heiner Meyer at the LUDWIGGALERIE Schloss Oberhausen. It is located centrally in front of the palace facade on Konrad-Adenauer-Allee and many people who drive past it will surely think: "How great!" But they may also involuntarily ask themselves: "How did it get here so quickly? My goodness, it seems to have fallen from the sky!" No, it hasn't. From the idea to the unveiling, it took a process that lasted about two years. We, the team at the LUDWIGGALERIE, find this so exciting that we would like to give our readers an insight over the next few weeks. We will therefore be publishing blog posts in no particular order with descriptions of the various trades involved in the creation process. We hope that you find these reports as exciting as we do and that they inspire you to take a look at the sculpture for yourself when you get the chance.

We start today with explanations of the statics of the sculptureDerived from Dr.-Ing. Christoph Diekmann, engineering office Diekmann in Oberhausen.

When Jutta Kruft-Lohrengel, 1st chairwoman of the LUDWIGGALERIE Friends' Circle, asked for the structural analysis of a sculpture intended for the LUDWIGGALERIE, my first reaction, which seems quite mundane today, was: I don't need structural analysis for my garden fountain either. But the obvious, structurally based question immediately popped into my head: Isn't a sculpture a building or a structure according to the state building regulations, for which structural analysis is required? Ultimately, the stability of a building has to be guaranteed, one way or another. So my reaction to such an unusual and not every day request was: "We'll see."

It quickly becomes clear that the artistic design calls for a sculpture approximately six metres high, made up of seven different shoe models arranged one above the other.

Arrangement of the shoes and designations of the surfaces © Statics report Ingenieurbüro Diekmann

This gives rise to a number of aspects that I need to consider:

sheet thickness and distortion

To ensure that the individual elements remain stable, a sheet thickness of around 30 mm was specified. The base plate must support a weight of around 2,2 tonnes and the components must not be distorted by welding or transport. Welding distortion can occur, for example, due to the heat supplied during welding. This causes the sheet metal parts to deform. This can be avoided by carefully planning the welding process.

The focus determination

Each of the individual shoe elements has its own geometry. This makes determining the focal points difficult. In order to reproduce the artistic design as faithfully as possible, the entire processing chain was carried out using 3D modeling software. The individual shapes were digitally taken from the artist Heiner Meyer's design and reproduced as a 3D model. A calculation model was then derived from this to determine the force distribution; the production data was generated in parallel. This ultimately serves as the basis for the computer-aided cutting of the sheet metal parts at Franken Apparatebau in Oberhausen.

susceptibility to wind

Each individual shoe model is around 1 m² in size, which means that there is a fairly significant area exposed to wind. In addition, each shoe element weighs around 300 kg, so that cantilevered details on the elements generate high connecting forces. In order to achieve a stable overall construction, the respective contact surface between two pieces must withstand high pressure and bending stresses.

contact surfaces

A major challenge arises from the fact that the elements sometimes only touch at certain points, meaning that there are only small contact surfaces. The transfer of the connecting forces therefore places special demands on the geometric design and the welding technology. (The contact surfaces are marked in blue.)

Shoe 5 with marked welds © Structural analysis report Ingenieurbüro Diekmann

Der Transport

The sculpture must be assembled in the workshop because assembly on site does not meet the high quality requirements described. This means that the large and heavy model must be moved around the workshop with a crane, transported on a low-loader and set up and assembled with a mobile crane. The forces generated in this process must also be safely transmitted through the welds at the contact points. The foundation is intended for installation. It is located next to the footpath in front of the castle and measures around 3,30 x 5,50 meters. The entire structure will be set up on this and anchored in place. Incidentally, the sculpture by the artist Keith Haring, Head through Belly, was previously on display there.

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The actual static calculation is the mathematical simulation of the loads on the sculpture to determine the force distribution. This is used to calculate the areas that are particularly stressed. This is an unusual task for the irregular and flat shoe elements in a spatial arrangement.