Two minutes with Davood Liaghat

Davood Liaghat

02/11/2012 Written by: Tracy Hobson

How did you make the choice to specialise in Bridge Engineering?

Bridge Engineering sort of chose me… I studied Civil Engineering in Bristol, then got the opportunity to go straight on to do a PhD, researching long span suspension bridges.  That research led me to join a firm of engineers specialising in long span steel bridges and undertaking strengthening works on one, the Severn Bridge.  I later moved to a company that specialised in concrete bridges and viaducts, before I joined the infrastructure team at BuroHappold with a remit to establish a Bridge Engineering team here in London.

So do you ever wish things had gone differently?

Not at all, I think that bridge engineering is one of the few areas where engineers get the opportunity to make practical use of a lot of what they’ve learnt about in their civil engineering course at university.  It’s a great mix of disciplines – structural,  geotechnical, aerodynamics, seismic  and of course infrastructure.

Bridges have their primary  function, which is to carry people, vehicles, trains , even utilities  over obstacles, but they are also extremely visual objects that people will notice, and unlike buildings in which the structural members tend to be hidden by cladding and façade, people can normally see exactly how a bridge has been constructed.  We work closely with our specialist colleagues, but do get a chance to input into many areas of engineering, which is very enjoyable.

Is there one bridge that you prize above all others?

We’ve built about 30 bridges in the last five years or so and each one has something unique about it.  Obviously larger projects like the Emirates Stadium bridges, or Stratford Town Centre Link stand out, but I suppose the one I’m most proud of is the Ponte della Musica in Rome.

Ponte della Musica is unusual because it is a relatively long river bridge (200m in total, with a 130m clear span), but it’s also very low in height.  The traditional way for bridges to cope with long spans is to have masts and cables, but this bridge was designed to nestle elegantly in its surroundings, so the low lying arches never reach above 10m high.  People will remember the problems which affected London’s Millennium Bridge when it first opened and the rhythm of people walking caused it to wobble quite disconcertingly, so one of our priorities was to avoid that problem. In addition, the design used no bracing of the arches and we were building out from soft ground, in a seismic zone.  It was a quite a challenging project, but definitely a fascinating and inspiring one.

This bridge has become an icon of Rome, much has been written about it some critical but overwhelmingly supportive. The bridge is shortlisted for the Institution of Structural Engineers Awards 2102.

How about moving bridges – they sound like they could be fun?

We’ve created a few moveable bridges, like the Novi Sad Friendship swing bridge in Norwich and the Princess Royal swing footbridge in Thorne, Yorkshire, The main challenge with these is to balance the weight of the span on a single tower or pedestal and to allow the deck to rotate in a controlled manner during rotation.  We use computer modelling, particularly the Finite Element method, extensively on these bridges, to help us test for structural behaviour under varied load distribution, static and/or dynamic. 

Any bridge engineering heroes?

Obviously after spending my formative years in Bristol, I’ve had plenty of time to appreciate the incredible achievement of Isambard Kingdom Brunel on the Clifton Suspension Bridge.  My first flat in Bristol was overlooking this wonderful bridge over the Avon gorge. Not only did he create a structure that inspires awe over 150 years later, but the difficulties he overcame in the process (three attempts to secure the commission, an incredibly tight budget, long delays and disruption) are a testament to his passion and audacity.  Recent studies have shown some remarkably modern design features in the bridge, such as the honeycomb of chambers inside each tower which reduces the weight while maintaining strength.  He was also recycling long before that word was invented - the chains used on the bridge came from an earlier bridge which had been demolished!

It’s not all about historical figures though, I think that the French engineer Michel Virlogeux is doing some incredible work today – the Millau Viaduct in France, co-designed with Lord Norman Foster, is a beautiful and impressive structure.

So what’s next?

We’re currently working on a number of projects in the Middle East, including a six-lane vehicular flyover  in Riyadh and a series of air-conditioned skywalks connect buildings in the King Abdullah Financial District of Riyadh.

We’re also undertaking a feasibility study at Nine Elms near Battersea and are supporting BuroHappold teams around the world on other bridge projects.

My ambition is to have helped to create a bridge in every major city in the world by the time I retire and I don’t think I’m doing too badly so far!

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