ICE Bridges 2014: Part One
Just over a week ago I was lucky enough to be invited to the ICE Bridges 2014 conference, which brought together some of the most prominent bridge engineers across the UK. Held in the awe-inspiring headquarters of the institution, the event had a packed program of seminars that took in everything from maintenance of our historic bridges, through to the future technologies that will shape design.
Chaired by Mike Chrimes, the talks were interspersed by opportunities to network, eat food from plates with integrated glass-holders, and take in the exhibition stalls presented by the multitude of sponsors. Before embarking on this three parter sharing the highlights of each talk, I think it’s worth mentioning that ICE Bridges 2014 was the last event that Mike (who’s 37 years at the institution included the digitisation of the ICE Library) would chair before retirement.
Roger Ridsdill-Smith (Foster + Partners)
Take [design] decisions by avoiding having things, not by adding them.
Famous for his involvement with the Millennium Bridge, I’d already seen Roger deliver a project talk for the IABSE. Interestingly, however, this lecture focused on introducing his philosophy of ‘inevitable design’: Design that is invisible; so obvious that it’s not even clear it was a decision. To establish his point, Roger used a picture of a park path. While the actual path took a scenic curve, there was a clear beaten track of dead grass along the shortest, straight, route. The foot-forged straight was the inevitable design, and by ignoring it the landscaper had created a redundant path.
When it comes to bridges, Roger sees the inevitable design as the alignment created by constraints. The Millennium Bridge had to keep shipping channels and the Southbank path open, and maintain the views of St Pauls. The famous cathedral also has a straight route along Peter’s Hill to the Thames. This creates an inevitable axis for the bridge with an inevitable alignment formed along the the river clearance, and an inevitable low-profile form. Arguably it was the constraints (or the inevitabilities) that created the solution (sounds like my definition of Elegant Design?).
Steve Nicholson (Mersey Gateway)
Projects will drive their own solutions as to what really means value for money.
As an engineer, especially a younger one, it’s easy to start thinking of bridges as things that will get built and need to be designed. That’s why, to me, Steve’s talk was so interesting, as it focused on his work getting the new Mersey Gateway Crossing to the stage where it will actually get built, and needs to be designed. Located at a point where everyone agrees the infrastructure is already at capacity, but no one public group thought it strategic enough to take ownership; Steve has seen the scheme picked up by Halton Council, working to find private funding and political acceptance.
Getting a bridge to the stage that it will actually get built appears to be an exercise in balance. You start with the relatively easy prospect of getting a road to cross a river, but then to justify the scheme to government it suddenly needs to do more than elevate traffic; and you find yourself adding second stories of public transport corridors and redeveloping the whole area. Then to get permission from the public you need to do everything you can to alleviate the impact on the environment, regardless of the cost- which ironically is the only thing the private investors you have to convince to pay for the structure care about. At the last, you’ve gambled 5 years and £40 million just to find out if you’ll be allowed to build the damn thing.
Steve attributes a failure to maintain this balance as the reason many schemes are never realised– the scope creeps beyond recovery and the cost escalates beyond that private investors could ever justify a return from, or agree a maintenance period for. But it is also this attitude that means that the new bridge will come at a cost of tolling (investors want tangible gain, not just the warm glow that comes from making the world a better place), and be formed from a conservative foundation; with contractors focusing on the familiar to afford the aggressive approaches to risk necessitated by the value engineering that comes from the continuous scrutiny of stakeholders.
Mariapia Angelino (Bristol University)
The opportunity to influence the second generation of Eurocodes is now.
Love ’em or hate ’em, the Eurocodes are here to stay. As the suite was conceived in 1975, however, it’s hard to think of them as anything other than holy writ, handed down from mysterious standards committees, that the forever put-upon engineer just has to cope with. But did you know that in 2013 a mandate was issued to begin writing the next generation of the Eurocodes, which, unlike their parents, will be available in six years time? That’s why Mariapia’s talk has me excited (in fact, this subject will be getting its own post…); here is a chance to influence the codes we’ll be using to design Crossrail 3…
So what can we expect from the Eurocodes and the Chamber of Secrets? Well, despite difficulties harmonising product standards across Europe, there’s a plan to extend beyond Europe, with work being undertaken to engage India, China, Africa and South America. On a more tangible note, Glass and FRP are being added to the material suite, with membrane forms being included alongside requirements for robustness and measuring climate change impact. Interestingly, the next generation of Eurocodes won’t just be for new structures, but will include methods of assessment for working with repairs and retro-fitting. Perhaps most exciting is that a key focus will be on addressing the most common complaint about them: they’re going to be easier to use!
Keith Ross (Network Rail)
Considering that there were 1645 bridge strikes in 2013 alone, engineers must do more.
After a talk from the “King of Bridge Strikes”, I expect you, too, will pause to consider if there is more you could do than just make a note of it on the risk assessment and chuck in a requirement for some signage. Frankly, the statistics are alarming: there were 1645 strikes (that’s just over 30 a week) to rail-over-road bridges alone in 2013, 443 of which were in Surrey, with the majority HGVs into 13′ and 14’6” clearances.
Depressingly, however, a study into why bridges are hit so often turned out that 32% of drivers didn’t know the height of their vehicle, 22% had planned their route badly (and, presumably, therefore decided just to go for it), and 8% of drivers simply didn’t believe the signs. Whilst this suggests that engineers are therefore powerless to stop them; Keith believes that we could do a lot to improve our signage, claiming that he’s yet to see a compliant set on any bridge. Pointing to the latest issue of “Prevention of Strikes on Bridges Over Highways“, he cites arches that force drivers into the middle of busy roads, obscured signs and lack of clear diversions as engineering failings which we must address.
Fernando Sarasa (Structural Reserach)
Our aim is to deliver to site, as much as we can, the finished product.
Fernando’s main achievement was to introduce me to the BSST (Bridges/Beams Spliced with Short Tendons) system that the Spanish have been extensively using for the last 20 years. Without spamming you with technical details, the BSST System is essentially a collection of precast pre/post-tensioned concrete elements that are placed together and then jointed (using minimal in-situ concrete) to form a structural member.
As well as gaining the inherent benefits of factory-quality pre-casting, the system creates a bridge that can be delivered and placed from the back of a lorry, and is configured in such a way that the elements form working platforms from which the the in-situ jointing between segments and thin top slab can be poured. This leads to 150m long bridges that can be read for service in 9 weeks; what more need be said?
Check-out Part 2 of the ICE Bridges 2014 highlights.