How aluminium is competing with steel on long suspension bridge girders
ZellaHyday > 01-06-2022, 07:35 AM
Both steel and aluminium are fine materials for bridges. But with suspension bridges, which include girders as structural components, the two materials are apparently not equally fine. No suspension bridges with aluminium girders have ever been built. I will argue that the time is right for change.
Aluminium has been used in bridge structures for nearly a century, starting with the Smithfield Street Bridge in Pittsburgh in 1933. They used a riveted aluminium construction to replace the existing steel-and-wood deck, to increase the load-carrying capacity of the bridge.
We then saw construction of the first all-aluminium bridge in 1950, in Canada. The bridge cost more than it would have had it been made from steel, but the builders expected this to be offset by significantly lower maintenance costs. The bridge is still in operation, and only minor maintenance work has been required.
Density and corrosion resistance are key properties
Properties such as density and corrosion resistance make aluminium well suited for bridge structures. For example, when rehabilitating existing bridges, lightweight aluminium deck structures are used to increase load-carrying capacity without replacing fundaments or the main structure of the bridge. The substantial reduction in weight also makes it easier to install larger sections, thus reducing installation time and cost.
Other benefits of using aluminium, as opposed to steel:
No maintenance or humidity control needed
When end-of-life recycling is included, aluminium normally has a lower CO2 footprint than steel
Aluminium is faster to fabricate
Design flexibility with extrusion, which also allows you to put material where it is needed
Environmentally friendly
Advantages of friction stir welding
Aluminium in suspension bridge girders
Suspension bridges get their name from the fact that the deck on such bridges is hung below suspension cables on vertical suspenders, which are anchored on each end. Girders are structural components of a suspension bridge. In fact, a suspension bridge is one continuous girder suspended by the cables.
Steel is the dominant construction material used for suspension bridge girders because it is strong and durable, and can flex without fracturing. Another factor is that materials engineers learned a lot more about steel than aluminium at school. That has been a key factor. But I am convinced that the more we learn and know about aluminium, the more that picture will change.