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Here’s why adaptability is the key to coping with transport disastersFloods caused by Storm Desmond left more than 2,500...
10/01/2022

Here’s why adaptability is the key to coping with transport disasters
Floods caused by Storm Desmond left more than 2,500 homes without power, washed away bridges, closed schools and hospitals and caused serious damage to homes and businesses across swathes of northern England and Scotland.

Meanwhile, the closure of the Forth Road Bridge due to structural defects has left 100,000 people, along with major corporations such as Amazon, facing large diversions and substantial delays. At times such as this, a cottage industry in back-of-the-envelope calculations rushes to estimate the disastrous costs to the economy.

Infrastructure failures and natural disasters are facts of life. While the agencies responsible for maintaining our infrastructure such as Network Rail and Transport Scotland seek to protect us against the biggest and most common problems, it rarely stacks up economically, financially or politically to guard against low probability, high risk events. And even if they did try to do this, they would be unable to cater for all possibilities. The risks posed by climate change and terrorism are notoriously difficult to predict, so significant failures of some kind would still occur.

Of course, the responses of emergency services and public transport providers do have a big impact on how quickly things can return to normal. Providing extra bus or rail services, and dedicated lanes for buses or goods vehicles, can help people to resume their daily routines. For example, in Edinburgh, an extra 11,000 bus seats and 6,500 rail seats are being provided to cope with the Forth Road Bridge closure. Even so, these measures are unlikely to match up to the numbers of people that would normally be on the roads, and train and bus stations probably are not ready to cope with such a big surge in demand.

Silver linings
So, instead of just trying to maintain our usual routines in the face of huge disruptions, we should see these events as opportunities to try out new ways of doing things and getting places. Indeed, there is a significant body of research which tells us that, if well managed, major changes to the availability or quality of transport and infrastructure services need not be catastrophic for quite so many people.

Flooding in Carlisle following Storm Desmond. Phil Noble/Reuters
A good example is the success of the travel management strategies put in place for the London Olympics in 2012, and the Glasgow Commonwealth Games in 2014. In both cities, significant efforts were made to adapt transport services. But these only worked when combined with the adaptability of businesses and the flexibility shown by commuters.

Yet this capacity for social adaptation can’t simply be switched on and off – it needs to be developed. Most of us have regular and clearly defined travel patterns, developed around the demands of our day-to-day lives: we base our home, work, schooling and leisure choices around an increasingly complex and time constrained pattern of journeys. And for each of these journeys, we have a set of expectations as to its likely length and quality, based on different modes of transport.

If we can relax some of the constraints around which we structure our everyday lives, then it will be much easier for us to adapt when things don’t go according to plan.

The path less travelled
For one thing, we can exercise a surprising amount of flexibility just by drawing on our social resources. Recent research on transport disruptions found that, for disturbances lasting up to a week, people were as likely to postpone and rearrange trips as to cancel them. Asking colleagues to assist with work trips, coordinating family or neighbours to help with school runs, and shopping in new locations can all help us to deal with disasters.

Likewise, where personal circumstances allow it, rearranging schedules and leaving earlier or later from jobs or activities can go a long way toward making disasters manageable. Workplace flexibility is crucial here: bosses must be adaptable when it comes to the timing of shifts, tolerating lateness or encouraging working from home.

It is much easier to take alternative routes or means of transport when you’ve tried them out before. Those who are already familiar with more than one way of getting to work are better able to adapt. The good news is that two-thirds of people already use more than one means of transport each week. And planned outages, such as strikes, can also offer less chaotic opportunities to experiment with new routes and modes of transport.

We will be more resilient to a range of problems if we foster a future where everyone is a little less dependent on their cars, and a little better equipped to manage without them. The added appeal of this approach is that travelling less by car more generally would also help us to tackle congestion problems, long-term climate change obligations and the obesity crisis, in ways which suring up our infrastructure will not.

There’s no doubt that engineering solutions such as flood defences and investment in preventative bridge and road maintenance have a major role to play when it comes to trying to prevent catastrophes. But as a society, we should also be trying to make it easier for people to be more flexible and also more multi-modal, more of the time.

Genoa bridge collapse: maintaining these structures is a constant battle against traffic and decayAs rescue workers look...
10/01/2022

Genoa bridge collapse: maintaining these structures is a constant battle against traffic and decay
As rescue workers look for survivors in the concrete rubble that used to be part of the Morandi bridge in Genoa, Italian authorities are starting their investigation into the possible causes behind this terrible tragedy.

It is too early to determine what may have caused the catastrophic collapse of more than 100 metres of the multi-span, cable-stayed suspension bridge, completed just over 50 years ago. But it’s important to understand that bridge engineering does not end when construction finishes and traffic starts to flow. In fact, properly looking after a bridge during its long life is as crucial as having a good design, using high-quality materials, and ensuring sound workmanship during construction.

Modern bridges are designed for a life of 100 years, though many centenarian bridges – such as the Forth Bridge in Scotland, which opened in 1890 – still provide sterling service, and of course there are smaller bridges built of stone to more ancient designs that have stood for many hundreds of years. Considering the number of bridges built in Europe during the expansion of the motorway networks from the late-1950s onwards, we should expect, and be prepared for, many to exceed their planned lifespan in coming decades. Facilitating this is ambitious but necessary, and made possible thanks only to regular inspection and maintenance that ensures that building materials have not degraded, and that structural elements are fit to bear the traffic and environmental loads they face.

The Forth Bridge outside Edinburgh, one of Britain’s iconic bridges, is more than 100 years old. Andrew Shiva
So what are the factors that affect the strength of a bridge and may compromise public safety?

Environment and climate
The climate in a bridge’s location, taken alongside atmospheric pollution common in cities, can have an adverse influence on the material of the bridge – for example, the corrosion of steel reinforcement or pre-stressed steel tendons embedded in concrete. Regular inspections are typically scheduled every six years for large bridges to identify any degradation, and to take appropriate measures to replace cracking concrete and corroded steel, or to introduce protective coatings.

In England, the Midlands Link motorway viaducts, comprising 13 miles of elevated motorway carrying the M5 and M6 motorways around Birmingham, suffered from chloride-induced steel corrosion early on in their life from exposure to salt used to de-ice the roads. This required an extensive application of corrosion protection measures in the early 1990s. More than 700 structures have benefited from this action, demonstrating the cost savings that can be made if appropriate action is taken at the right time.

Stress and fatigue
Fatigue caused by use is another factor, and inspectors will look out for tell-tale signs of failure often associated with the cyclical stress produced by passing vehicles, particularly heavy trucks. This type of failure is especially relevant for metal bridge decks and the cables of suspension and cable-stayed bridges. Traffic has increased ever since these bridges were built, which inevitably leads to the need for more maintenance and strengthening work, such as additional steel, glass or carbon fibre-reinforced plates on critical parts in order to restore or enhance their strength compared to what was deemed necessary during their design. For example, Network Rail in the UK used fibre-reinforced polymers to strengthen more than 20 bridges carrying highway or railway traffic between 2001 and 2010.

Consider how we all tend to react to a road sign bearing the words: “Essential Bridge Works – Expect Long Delays”. One such situation prompted this comment from a member of the public: “We are doomed. I am going to buy a tent and pitch it outside work for the three months while the misery goes on.” Perhaps knowing why this is necessary – and the consequences of not doing so – might persuade people to reconsider such views.

Money and willingness to spend it
Equally, we must understand that maintenance budgets need to be set at levels that far exceed those that would allow engineers only to “firefight” the most severe problems, as is becoming worryingly commonplace. Instead, budgets need to allow for planned interventions and necessary upgrades over many decades. That requires public and government support, as well as skilled engineers committed to ensuring the safety of an ageing structure.

There are challenges in devising improved methods to assess bridge strength, developing new repair techniques, and new ways of collecting and using inspection and monitoring data to provide advance warning of problems. These constantly push technological boundaries, making it possible to operate existing bridges safely during their long service lives. And the experience gained feeds into new designs that will become reality in years to come.

Those investigating the collapse of the Morandi bridge will look at inspection and maintenance matters. Other lines of enquiry will no doubt include the unusual design of the multi-span bridge, with only a few cable stays to transfer deck loads to the towers, the ongoing work to shore up the foundations, and the heavy rainfall at the time of the collapse. In the shadow of this terrible loss of life, it is worth remembering that bridge inspection and maintenance may be annoying for commuters – but it is crucial.

Are Australian bridges safe, and can we do better?After the tragedy in the Italian city Genoa, where a highway bridge co...
10/01/2022

Are Australian bridges safe, and can we do better?
After the tragedy in the Italian city Genoa, where a highway bridge collapsed killing more than 40 people, nations seem to be taking stock of the maintenance levels of their bridges. There are reports thousands of UK bridges are at risk of collapse, and there are hundreds of similarly damaged bridges in France, Germany and Italy itself.

Australia is no different to other developed countries in this regard, where a lot of bridges are old and deteriorating, and we would be foolish to think we are immune. That said, bridges are generally safe structures, with the risk of fatality from a bridge collapse being around one in 100 million per year. This is roughly 100 times less likely than being killed by lightning.

So yes, our bridges are safe, but they need to be kept up-to-date to maintain these low statistics. So how are bridges in Australia managed, and who is responsible?

The age of Australia’s bridges
Bridges are nominally designed to last for some long period of time, such as 100 years. However, such claims are reasonably arbitrary, since much of the technology used in bridge construction hasn’t even existed for 100 years.

Accelerated deterioration testing in laboratories does help make predictions, but it’s not necessarily a good reflection of field performance. This is because of differences between naturally occurring, and artificially impressed, corrosion.

Both age and traffic volume are significant factors in the rate of deterioration of bridge surfaces. Age is likely a proxy for the combination of weather effects and the natural degradation of the material. To combat these effects, inspections and maintenance – or better yet, live monitoring – of bridges, are the best ways we have to ensure public safety.

In Australia, around 800 organisations are responsible for around 53,000 public road bridges. Some (about 23,000) are managed by state road authorities, who manage the high-capacity arterial roads, and local councils who manage the remaining local roads (about 30,000). Of course, the eight state and territory road authorities are the main road bridge owners.

Both age and traffic volume are significant factors in the rate of deterioration of bridge surfaces. (The West Gate Bridge, in Melbourne). from shutterstock.com
Bridge safety, as with all structural engineering, is a question of whether the imparted load is less than the structure’s strength. Since loads and material strengths are variable, high estimates of loads are used, and low estimates of strengths are used. These extreme (high) loads and (low) strengths are further factored to achieve an acceptably small probability of failure when checking structural adequacy.

Highway traffic loads are known as “normal” when referring to everyday ordinary loading and “abnormal” in the case of special heavy transport. The high estimate of normal traffic loading represents a once in a 1000-year likelihood of a critical event (known as the return period). Abnormal special vehicles might be 300 or 400 tonne loads. During movements of these vehicles, no other traffic will be permitted on the bridge.

Read more: Explainer: why do bridges collapse?

Before 1950 Australia’s road bridges were built to design standards set at state level. Around 15% of our bridges on main roads come from this era.

Considering normal traffic use, from 1950 to 1976 short-to-medium span bridges were designed for the MS18 load model. This is roughly a 33 tonne semi-trailer vehicle, or about 20 cars. These now comprise about 50% of the bridge network. From 1976 to 2004 it was the T44 load model, or roughly a 44-tonne vehicle, and these are about 25% of the network. Today, it is the M1600 load model (roughly a 160-tonne vehicle) and these make up about 10% of the network.

These load models have different weight and other aspects, so it isn’t meaningful to rely on the quoted gross weight – it strongly depends on how that load is distributed, and the other factors involved. Still, the loads bridges are designed for have increased together with legal truck weight limits, which themselves have increased by about 10% per decade since the 1950s.

So, how healthy are Australian bridges?
In Australia there are mostly three levels of bridge examination, but NSW has a fourth level. Level 1 inspections are essentially drive-bys to ensure there are no gross deformities present. This takes place roughly twice a year. Level 2 inspections are an “arms-length” visual inspection of all bridge surfaces and components and should take place around every five years at most. The scope of what is included in Level 2 inspections varies across jurisdictions.

Level 3 inspections are detailed engineering inspections, including material sampling and structural modelling. NSW’s level 4 inspections are typically proof load testing. Level 3 (and 4) inspections take place in special circumstances, such as a natural hazard, or change in legal load limits.

The Genoa Morandi bridge will hopefully make sure authorities around the world are more vigilant about ageing infrastructure. LUCA ZENNARO/EPA
Unfortunately, it’s difficult to give a snapshot of the current state of Australia’s bridges. The state road authorities make public very little information about bridge conditions, or inspection and maintenance budgets. In South Australia, bridge inspection results are not available, even under Freedom of Information it seems. Tasmania, the ACT, and NSW offer no data, at least from their websites.

Queensland data is available via email, but has no inspection information. Western Australia offers a GIS interface, but again no inspection data. Victoria seems to be best, offering a GIS website, which includes condition ratings (using Vicroads’ own Bridge Condition Number).

Read more: Genoa bridge collapse: maintaining these structures is a constant battle against traffic and decay

What could we do better?
An open access national bridge inventory, such as exists in the United States, would be of enormous benefit in the study and management of Australia’s bridges. For this to happen, harmonisation of inspection and maintenance routines would be necessary, along with condition rating schemes.

While the present system reflects environmental, practice, and legislative differences between the states and territories, a reasonably general national system with jurisdiction-level tuning is surely feasible.

Risk assessments should move away from subjective qualitative approaches, and adopt an objective quantitative framework. This should help minimise problems associated with loss of corporate knowledge (which contributes to collapses). Such quantitative safety data would enable budgeting for inspection and maintenance to be done on a needs basis, with clear reference to minimum acceptable levels of safety.

There are no simple answers to the complex problems bridge management throws up. The ideal combination of field inspection, expert technical knowledge, management processes, and political decision-making is hard to find. Nevertheless, the case of the Ponte Morandi in Genoa should serve as sufficient warning to be vigilant.

It might be some comfort to the families of the 43 people who died to know their loss has motivated agencies around the world to ensure foreseeable bridge failures are prevented.

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