Complex repairs begin tomorrow night on a key piece of Auckland’s roading infrastructure.
Friday’s accident closed half the lanes on the Auckland Harbour Bridge, resulting in heavy delays for commuters. The bridge’s southbound lanes will be closed overnight Tuesday to install a temporary repair strut.
The SMC asked experts to comment on the incident and the potential for a new harbour crossing.
Dr Theuns Henning, Senior Lecturer, Faculty of Engineering, University of Auckland and CEO for IDS (Infrastructure Decision Support), comments:
“The Auckland Harbour Bridge is an example of why investment in infrastructure planning and a commitment to ongoing maintenance is so important. The truck incident on Friday was a freak event that could not have been foreseen. The Auckland Harbour Bridge is well maintained and the right protocols are in place for strong winds. The consequences could have been much worse had an efficient infrastructure maintenance plan not been in place. This reinforces the importance of investing in infrastructure, as the consequences of losing the full use of critical infrastructure has significant implications.”
No conflict of interest
Professor John Tookey, Professor of Construction, Auckland University of Technology, comments:
“The last weekend’s damage to the Auckland harbour bridge threw into stark relief quite how dependent we are on a single piece of infrastructure. A non-fatal (thankfully) accident on the bridge leads to damage that will impact traffic flows and economic activity for weeks if not months. Cue collective meltdown amongst commentators and commuters alike. This is alas no surprise. The bridge looks very similar to an overlarge Meccano set of columns, beams and struts. However, the replacement components cannot simply be rustled up by a short search down the back of our collective city-wide sofa. The strut needing to be replaced will have to be specifically fabricated to demanding tolerances. The process of installation itself is not an inconsiderable task. All to be undertaken while maintaining as much of the functional capacity as possible for the bridge. Not straightforward. Bottom line – it is going to take as long as it takes.
“For most practical purposes the infrastructure that we have in place very quickly becomes immutable. It seems to always have been there. Increasingly there are few people who remember a time before the bridge. Inevitable really with a structure completed in 1959. However, we similarly tend to forget that there was a time before the Greenhithe bridge. If that were not in place now, Auckland would be absolutely in the mire. However, think how rapidly we all absorbed the new Waterview tunnel and its ability to provide access to the South and the airport. We rapidly forget just how much time and effort we used to spend in getting around this city. The value of improved and enhanced infrastructure cannot be understated. At present we are very exposed to the impact of a myriad of potential events covering freak weather, seismic activity or even terrorism. We have seen multiple instances of accidents and incidents causing chaos throughout the city. Either by chance or design it is relatively easy to shut down Auckland economically and socially.
“The question most Aucklanders are increasingly asking is when do we press the button? When do we develop a new harbour crossing? This is something that should have been front and centre in most people’s estimation for a number of years. We have had various studies seeking to examine how long we can eke out the bridge without biting the bullet of new investment. It is hard not to look at the discussions had since the last round of clip-on improvements in 2009. At that point in time NZTA noted that the clip-ons could not be strengthened again but works had extended life by 20 years or more. However, they required trucks to only use the central lanes – which was part of the issue this time. Lately various options for a crossing have been considered with a tunnel being preferred. Today, Mayor Goff announced that a new crossing was a priority with work expected to start by the end of the decade. Are we talking construction or just developing design we wonder? If the latter then this means that we are likely to see a tunnel in place by 2038 or so on the basis of this timeline. To be honest this smacks of kicking the can down the road to another administration. The fact that $8bn has been mentioned for this project is not a number designed to encourage commitment. It is noticeable that when the regular re-litigation of whether or not to have a stadium on the waterfront comes up that projected costs are much more optimistically set. Similarly when the SkyPath was pitched for funding under the government’s ‘shovel ready’ scheme, money was found. Irrespective of the fact that the project was not ‘shovel ready’ and the value of the infrastructure for making Auckland work better is at best marginal. I guess it comes down to priorities, right?
“As it stands, the delay to full bridge operation could not have come at a better time. Restrictions on office opening and large numbers of workers working from home as a result of COVID-19 lockdown requirements have already effectively reduced bridge traffic. Similarly many of us are already prepared to move back into a distance working mode in short order. For the first time in 2020 we can actually point to something that COVID-19 has actually had a positive impact upon! Notwithstanding which, there is a deep and expanding need to take the pressure off this vital piece of our city infrastructure in order to maintain that idea of being a liveable city for the future. Just to add an extra layer of optimism, the Harbour Bridge itself was actually delivered both under budget and ahead of schedule. If we could do it then, we can do it now. Provided we do not overload expectations into this investment, it is totally achievable.”
No conflict of interest.
Alessandro Palermo, Professor in Structural Engineering, Department of Civil and Natural Resources Engineering, University of Canterbury, comments:
The damage/repair
“Designing and building the strut shouldn’t take long. Probably 2-3 weeks. However, rigorous internal checks on the design and the installation can certainly slow down the process. I believe that the installation is the most critical part since it will be quite complex to reinstate the original load redistribution of the bridge. More importantly, a situation like this, i.e. replacing a damaged strut, is unique and engineers usually factor in some extra time to make sure everything is done correctly.”
Maintenance
“The Auckland Harbour Bridge is more than a 60-year-old bridge. At the time the bridge was built, the targeted design life was 50 years. Similarly to a person when you get old, the cost to maintain your performance is higher—more regular checks, more interventions etc. But differently from a person, a bridge is asked to perform more within the time since the traffic load keeps increasing.
“An Alliance was created in 1999 dedicated to protecting this important asset since the bridge was close to its design life. New bridges are designed for longer life (100 years) that means that to maintain the asset costs less.
“The Auckland Harbour Bridge is unique since it went through several variations/extensions that make the overall maintenance more complex.”
Moving forward
“The accident we had on Friday was unique and probably teaches that better traffic control management may help in the future to prevent damage to the structure. The additional Nippon clip-on increased the number of traffic lanes but also exposed the main structure to potential collisions. I think protecting the struts could be possible but has to be done such that engineers can inspect them easily when they do their routine maintenance checks.”
Lessons learnt
“Having a sole link and relying on one structure is not resilient for the city and any unexpected event can cause massive disruption to our economy. More importantly, past research confirmed that bridge trusses are more expensive to maintain. A single truck has caused damage of more than a few thousand dollars to the structure, but millions of dollars to our economy. People talk about the cost of building a new bridge or a tunnel, but the main questions we should be asking is, ‘How long are we continuing to extend the life of the bridge and at what cost to New Zealanders?” Examples from overseas have shown that an alternative can be designed and built in a timeframe of four to five years at most. Although in a different environmental context, the design and reconstruction of the Morandi Bridge in Genoa, which collapsed on 14 August 2018, happened in less than two years and the total length of the bridge is similar to the Auckland Harbour Bridge (more than 1km).”
No conflict of interest.