Expert: Veto Varma - 1/1/2011

Question
It has always been my dream since a child that one day we will be able to build bridges without pillars for support so that we can build sea bridges easily.is this a realistic vision or am i building bridges in the air? if yes can you please tell me what kind of design will have to be introduced with which materials to make it possible?

Answer
Hi,

It's always been a dream of civil engineers to make bridges more efficient and smart. Making longer span bridges are one of them.

In reality, because of gravity,  bridges needs to be supported somewhere, that means it needs columns, but by increasing the unsupported length of the bridges it is possible to minimize number of columns. Optimizing the unsupported length depends on many factors such as traffic loading, ground conditions, material used for bridge, other loading factors such as waves, water interaction, seismic etc...

Civil engineers has come up with many solutions for this problem. One of the excellent idea is to use cable supported bridges, this allows minimization of columns. Span is supported by cable coming from this massive column.  Cantilever type bridges are most common that allows bridge  cantilevering on both sides, this couples with prestressing forces allows to use longer unsupported spans.

There is lot of research being carried out to use more efficient concrete e.g. making it lighter, reducing reinforcements, using fly ash, smart concrete etc. You can found this research online on university web sites and in journal papers.

So in all it is possible to make longer span bridges, but in current technology it is limited to certain extent. Hope this helps.

Regards
Veto