Siemens Combino

Siemens Transportation System’s Streetcar

Prehistory
With the Combino; Siemens Transportation Systems put a modular designable streetcar with 100 percent of low floor technology into operation in 1998 for the first time. At that time the Combino was designed according to the branch-usual norm VDV 152 and the underlying load assumptions. Nevertheless, in subsequent operations measurements proved that initiated forces from the railway track were clearly greater in the vehicle than expected. The result: The vehicles were loaded severely. In an early phase of the investigations in autumn 2003, it was already clear to the Siemens experts that only one combination of discharges (renovation step 1) and a strengthening of the carriage boxes (renovation step 2) would lead to a lasting reduction of the loads.

Renovation step 1: Discharging measures

To slow down the damage mechanism clearly and therefore to maintain the operational safety of the used vehicles, measures had to be implemented at short notice in renovation step 1. In the first step wheel rolling bearings and open way dampers were used between the carriage boxes, which damped the distortion of the carriage boxes effectively already.

Renovation step 2: Strengthening of the carriage boxes - concept and simulation
The damping of the rotary movement of the chassis contributed to the essential discharge of the body-in-white structure carried out in the course of renovation step 2. Effectively the steering forces were reduced through the consumption of impact energy. This led to a 50-percent reduction of the strength peak initiated in the carriage box. The focus of renovation step 2 was to substitute for the overloaded bolt angle which connected the extrusion profiles with each other. In designing the strengthening measures great development expenditure was necessary. Therefore, the Bertrandt simulation team of the Cologne subsidiary was consulted for support. Because this development took place in a tight time window, the Bertrandt engineers were directly assigned at the development centre at Siemens. Thus, the Siemens design department could implement the concepts for the component load reduction fast in close collaboration. Bertrandt’s simulations were a central part in order to speed up development further. With the designing of the strengthening measures weight, design and functionality of the vehicle had to be maintained. The torsional stiffness of the carriage boxes was likewise not supposed to be lifted substantially, because this would have had cause the increase of the torsional strength immediately.


Final main entrance strengthening saves additional weight

The new solution distinguishes itself through metal, extrusion, casting and forging parts which are bolted together onto the existing structure and are welded together. The welded final main entrance strengthening is used for to the middle as well as in the chassis and head modules. It does not only prove an elegant solution for the greatest loaded places of the vehicle, but, furthermore, saves weight compared to the original solution. Now the upper corner of the main entrance is likewise bridged with a welded design. 

Double edge links prevents material fatigue

At the junctions of the window and door columns to the upper belt the priority consisted of substituting the clearly overloaded extrusions with suitable constructions. Also the advanced material fatigue in the upper belt was taken into consideration. The principle solution; a double edge link; therefore, consists of a lengthening of the column which reaches on a higher, intact level of the upper belt without having to consider door or folding window edges. The strengthening element is an aluminium forging part with which the connection to the upper belt is a screw, which connection with the door and window column is designed as a welding connection.

Sustainability checked

Finally the computational and experimental analyses of the long-term and operational stiffness were combined with each other to prove the sustainability of the developed solution.

Conclusion
With the realisation of simulations in track vehicle manufacturing Bertrandt has made the breakthrough into a new scope of duties. After two years of successful collaboration between Siemens Transportation Systems and Bertrandt the first renovated vehicles were put into operation again completely in summer 2005.