In the years 1895/96, the detail planning for the construction of the Wuppertal Suspension Railway had begun. At the end of the 19th century, steel engineering was still a relatively new field of construction. Only after the creation of the first major steel structures, including the Wuppertal Suspension Railway, were the calculations actually tested and confirmed. Nevertheless, the engineers of the suspension railway had performed their planning and design carefully. And so the railway commenced operation, suspended securely under girders and supports.

Patent solution: the design

The suspension railway framework consists of "standard supports" and "standard bridges". The supports are installed as pendulum and anchor supports on the line, and as heavy pendulum and anchor supports in the stops. They have a height of around 15m above the Wupper river, and a height of around 8m above the roads on the rural section. The standard bridges are 21m, 24m, 27m, 30m and 33m long. They are spatial frameworks with a central vertical main girder, the top flange of which is attached to a horizontal framework girder. The lower horizontal girder bearing the exterior rail brackets is arranged on the same level as the lower flange of the vertical main girder. The rails of the suspension railway are supported on the rail brackets on both sides of the bridges. They are located at intervals of around 4m from one another.

In order to make the system that transmits the load of the vehicles from the rail to the main girder stable, the construction process utilised so-called "hanging rods". This design innovation is the truly special feature of the patent registered by Anton Rieppel, the chief designer of the suspension railway.

Precise and exact: the calculation

The calculation of what was then a new supporting structure incorporated the static and physical parameters for the dead weight of the steel structure, the fittings, wind forces, temperature fluctuations, the vibrations and shock loads from the startup and braking forces of the suspension railway trains, as well as the dead weights of the trains.

Today calculations are based on complex mathematical models, which can be reliably and economically prepared using modern computers. All calculations are checked by independent engineers to ensure that they are complete and correct, in order to guarantee that the structure is safe and the corresponding regulations under construction legislation have been complied with.

Certified safety: the materials

The new structural steel grades today correspond in essence to the European regulations for building materials. In some respects, it has been necessary to expand these requirements by adding extra quality characteristics for reasons of the specific functional requirements. The structural steel, rivets and forged steel have precise material designations. The quality of the base material is inspected each by independent institutes directly at the steelworks. The results of this monitoring are documented in an acceptance inspection certificate, and attached to the file on the structure.

Holding together: the rivets

Due to the high and changing loads that occur during subsequent operation, the unremittingly meticulous manufacturing and inspection of the individual components is indispensable.

The riveting method actually fell out of in use in steel engineering in the 60s. In principle, however, this process technology has not changed. The muscle power that had to be applied then has simply been replaced today by mechanical power. 

The rivet is heated in the electric furnace until white-hot, picked up with the riveting pliers, descaled, and then inserted into the waiting hole. The factory head now has to be positioned in the dolly of the riveting tool, and pressed tightly against the workpiece. This tool is the same shape as the head of the rivet. The rivet must also be precisely the right length. The shop head is formed by the bucking tool integrated into the rivet clamp. The requisite force of up to 500kN is supplied by a hydraulic cylinder. The bridge structures are fully assembled in the workshops, and are delivered in a single piece.

Example of today's load assumptions: rolling load of articulated train carriage

Continuous load g=1.200 kg/m
Rails, cable lines, walkway g=295kg/m
Personnel safety system g=100kg/m
Wind pressure W=2,5kN/m Brückenanlage
Wind pressure on vehicle body W=17,6 kN/pro Laufwerk
Centrifugal force H=0,24F
Rolling load (walkway) p = 1,25 kN/m2
Vibration coefficient Average = 1.2