ICE Bridges 2014: Part Three
With 15 speakers, it’s fair to say that ICE Bridges 2014 was a packed event, and, despite dedicating three whole articles to the day, the best I can achieve is this overview of some of the highlights. Unfortunately, with all that dynamic networking, I didn’t manage to get a real look at the stands over the day. At a conference like this, however, it is the speakers who are the heart of the show. If you haven’t already, you can catch-up with the previous two parts here and here respectively.
As we hit the final part of this series, it seems worth finding some Springer’esq final thought to the whole affair. For me the event spoke of how future engineers will focus on maintaining our old infrastructure and working out how to design and build only the most cutting-edge bridges- whilst technology will permeate the construction of new turn-key structures; creating a market for prefabricated off-the-shelf solutions that prefer speed and standardisation over bespoke savings.
Bill Harvey (Bill Harvey Associates)
Before doing any monitoring, always ask yourself: “Is it a fair test?”
Like most Twitter fearing Engineers, the thought of accidentally misquoting Dr Harvey is enough to make me put down my scale rule, especially when it was one of the most technical talks of the event, and even more especially considering that he’s already written it up much better in a paper of his own. So, instead, I thought I’d share with you what I learnt from his presentation about replacing the Cleddau Viaduct bearings…
- Make sure you really understand a structure before you start working with it; it was a poorly conceived retro-fitted splice that threatened the viaduct.
- Remember that people will need to access your structures’ components; consider whether you would be able to inspect and replace them…
- Think about what you want to know before you start monitoring- and then think about how your monitoring regime will measure it, in scale, frequency and interval.
- Understand tolerance, especially when crossing between disciplines; mechanical tolerance is easily a factor of 10 away from construction tolerance.
Barry Colford (FETA)
The challenge with suspension bridges is that you don’t know the state of the principle elements.
So what does a Bridge Master do? Well, from where I’m standing it seems they spend their days trying to keep their bridge alive. Over the last 50 years the loading across the Forth Road Bridge has reached double the design load, the discovery of cable corrosion predicted that it would collapse in 2014, and now six times the original amount of traffic depends on it. Initially costing £11.5m to build, the cumulative spend on this Forth has reached £275m- a lesson in the importance of designing for durability and ease of maintenance if ever there was one. And whilst dehumidification has been somewhat successful, a replacement is under construction and the bridge seems destined to live out the remaining 70 years of its design life in a crippled state.
The principle challenge to mastering the Forth Road Bridge is that all the key elements are hidden. Whilst acoustic monitoring solutions now exist to ‘listen’ for the sound of breaking cable fibres; they’re only useful if you know how many working cables you have at the start. The cost of unravelling (especially with the risks of working over such a major route) even tiny samples of cable is phenomenal; requiring significant extrapolation and great uncertainties. To make matters worse, the anchorages are grouted underwater with only a rose-tinted ICE paper documenting how successful their installation was.
If it wasn’t for the toll, Colford believes the bridge would never have justified the cost of keeping it maintained for as long as it has been- citing impossible to replace bearings and the struggles of re-painting trusses as even simple design failings that make the structure unmaintainable. He finished by re-iterating his point from the panel: when it comes to maintenance the material cost nothing, the labour cost something, but gaining access costs everything.
Lawrence Shackman (T/port Scotland)
ITS is expected to reduce accidents by 26%, and has already saved 8 minutes on peek journey times.
From the old to the new- Lawrence’s talk focused on how ITS’ (Intelligent Transport Systems) have, and will, be used on the replacement Forth Road Crossing. In essence ITS’ are “managed motorways“, a combination of traffic monitoring and feedback that allow critical infrastructure to be controlled, so that it can adapt to situations as they develop. As part of the overall Forth plan they’ll enable the use of hard-shoulder running to maintain public transport reliability, control speed limits to smooth traffic and reduce chain-reaction accidents, and employ the old bridge as a dedicated ‘lighter-loading’ public transport corridor.
Peter Clapham (Unity Partnership)
The best way for authorities to achieve best practice is by having a framework to share their collective knowledge and experience.
It’s a little before my time, but in the 1970s it seems there was a vouge for redefining collections of boroughs into pseudo-cities, and then dissolving their responsibilities back to a local level 10 years later; Greater Manchester is an example of this. The Unity Partnership (which is essentially an embryonic LoBEG for the metropolitan county) is an attempt to solve the mismatch that comes from working ‘city’-wide infrastructure issues at individual local levels- a re-centralisation of asset management, if you will.
The Unity in said partnership, however, also includes a public/private partnership with Mouchel. The theory is that the boroughs can collaborate on projects to save money both by sharing project set-up costs, and with additional weight when engaging engineering firms. They can also take a city-wide view of asset maintenance; more easily realising the responsibilities that engineers have to their ageing infrastructure, despite 30% budget cuts. According to Peter, it seems to be working…
Campbell Middleton (Cambridge Uni.)
It’s crazy that we don’t just pick short bridges from off the shelf; pre-cast and pre-calculated.
Starting with the fairly brave assertion that we haven’t really changed the way we design and build bridges over the last 50 years, Campbell’s talk focused on areas where technology may innovate our structures in the not-to-distant future. Of interest to HS2 must have been the Explore Industrial Park (EIP), which is spearheading the Accelerated Bridge Construction approach already used in America to turn our ‘standard’ bridges into off-the-shelf products for clients to buy and assemble. He also made a call for a more encompassing BIM standard to store more esoteric measures such as residual life and serviceability.
Perhaps his most exciting points (the more standard promises of new materials and analysis techniques aside) surrounded developments in monitoring; the use of fibre optics to get real-time information about how structures are behaving, employing wireless sensor networks to easily share this information, the advent of micro-electromechanical systems to make monitoring more affordable and computer vision to make all the data useful. His examples included bridges where the monitoring showed none of the piles where being utilised, and Augmented Reality tools where videos were seamlessly converted into 3D models.
My favourite part, and a good note to end this series on, was his Holy Grails of engineering problems that, despite all these new innovations, we still haven’t solved:
- We can’t accurately calculate the ultimate shear capacity of concrete.
- We can’t reliably locate where reinforcement has been placed in complex sections.
- We can’t detect how much steel in concrete has corroded.
- We can’t monitor fatigue in steel.
- We can’t measure the true strength of our materials.
Here’s to the future…