The Story Bridge in Brisbane has the sad primacy of being the Australia’s most notorious suicide hotspot. As a prevention measure, the municipality finances a huge project with 8.4 mio AUD for adding a stainless steel mash wall all along both walkways.
Special beams 80x80x6x6mm
Low impact laser welded & polished
Architecture, Building & Construction
Special 316L Polished off-centered Beams
The completion announced for 2013, was postponed twice. Several factors were responsible for these delays; such as heritage issues about the aesthetic of the longest cantilever bridge of Australia, as well as improvements to the design of the mesh to allow for a better view.
Montanstahl has been involved in the project for producing and supplying the stainless steel poles. In early stage they were designed as hollow sections with variable cross section over the pole’s length. The following revision was for a beam with tapered height (of which some prototypes were produced and flown to Australia for evaluation).
A beam with off-centered web and constant cross section is the final choice (80x80x6x6mm). There were two different supply lengths: 3.4m and 4.5m. The selected material was stainless steel 316L. The surface must had to be polished to a surface roughness of max. Ra 0.7μ to ease electro polishing process. This process is improving additional corrosion resistance of the material.
The Solution: Low Impact Laser Welding Technology
The characteristics required for these beams have guided us towards the choice of the low impact laser welding technology. This special laser welding technology uses a special laser that grants reduced heat input with little deformation and minimal weld splatters.
Both aspects are very important, as the plates must be polished prior to laser welding. This allows for significant savings and a better polishing execution compared to a polishing performed afterwards on the finished section.
Any deformation of the bar, that leads to additional straightening processes, might affect the surface, which is unfavorable.
Also the reduction of the splatters, thanks to the Low Impact laser, is very important to avoid damaging the precious surface which was previously generated.
Also the overall dimensional tolerances are quiet demanding, as a clamp for fixing the mash will be connected and the pole has to fit exactly, should the pole be too small or too big, it wouldn’t match.
On Time Delivery is a Must
Due to all previous delays, the time schedule were very tight. However, an optimized and properly organized production, with definition of priority lists of the needed lengths, made everything run smoothly through production.
There was the customer request for performing the following steps on each single pole once produced:
inspection, dimensional measurement with relevant protocol, packaging in air cushions and finally storing in dedicated wooden boxes.
Some containers left the warehouse even before the agreed schedule.
Last Step Performed in Australia
Once in Australia each pole was machined for installation of the connection of the mesh fixation. The pole was bent with rolls to design radius and finally electro polished in order to increase corrosion resistant properties and consequently increasing lifetime.
The installation did not affect the aesthetics of the heritage-listed steel cantilever bridge at all, but will prevent from jumping deaths.