Melbourne is the fastest growing city in Australia and its population is set to more than double over the next 25 years. So what does this mean for our ageing infrastructure?
When the West Gate Bridge was finally completed in 1978, Melbourne’s population was just under three million.
Expansion in the west had necessitated the bridge build, which was designed to carry a strict number of vehicles and to last 100-150 years. However, since then development and population growth has increased beyond initial forecasts, to the point where heavy vehicles are no longer permitted to use the bridge.
Given that many of Melbourne’s bridges, buildings, sewage systems, transport systems and highways were constructed in the late 19th Century or during the post-war boom, and in light of the increase in use of these structures, how much do we know about their durability and structural integrity?
For Dr Saman De Silva, senior lecturer in the School of Engineering at RMIT University, this is one of the most important challenges facing the engineering industry today.
“We are experiencing an intense period of urbanisation where lifestyles have changed and younger generations are opting to live in the city,” he said.
“In the CBD, residential towers are rapidly being built to meet demand, while in the suburbs the skyline is also changing as councils approve more planning requests to build eight to ten-storey dwellings, resulting in a high-density situation.
“When it comes to transportation, we have good freeways but no ring road to connect them so the entry points to the city become clogged as people need to travel across town.
“This is not as critical as other cities – we are not at breaking point yet – but these expectations are putting pressure on asset owners, urban planners, designers and developers.”
De Silva said there are two major constraints when building, and later maintaining infrastructure.
“The first is unplanned or unexpected increases in demand, and the second has to do with degradation of existing structures and the lack of reliable asset condition data,” he said.
“At present, there’s a need for experts who can assess existing infrastructure and collect asset condition data to ensure ‘fitness for purpose’.”
From a safety point of view, De Silva assures that Australia’s buildings are structurally sound compared to many other developed cities, thanks to a well-regulated industry.
“Engineering in Australia is an industry with governance and assuming planners and approvers are doing their job, there is no conceivable concern with new high-rise residential tower developments or with our older buildings,” he said.
“One of the areas we are currently looking into is the fastening industry.
“Our know-how when it comes to the lifecycle of riveted connections is limited, so understanding the durability and the assessment of connections that were constructed 100 years ago is becoming important.”
Most of Melbourne’s infrastructure is owned and managed by government or private asset owners, for example Metro owns the trains; VicRoads manages roads; City West Water, South East Water, Yarra Valley Water and Melbourne Water looks after sewage, water and storm water drainage systems; and Transurban maintains the toll roads.
These asset owners are working closely with research and academic institutes to ensure scientific methods and cutting-edge knowledge is applied in order to measure the state of their infrastructure.
The knowledge and skills in assessing and retrofitting, especially after a disaster or an extreme event such as an earthquake or bushfire, is becoming a highly valued skill in the industry.
According to De Silva, we require engineers with an advanced understanding of structure and forensics.
“To draw a parallel, it is an important and highly-specialised area, like neurosurgery is to general surgery,” he said.
“This niche area of engineering is growing rapidly and there’s a shortage of qualified structural engineers who can manage our ageing assets and assess their safety and fitness for purpose.
“Most engineering programs focus predominantly on design, but now we are realising that up skilling is required for engineers who are interested in age care of existing structures.
“When asked if they can design a new five-storey building, most early-career structural engineers would say yes, however they might struggle to calculate the remaining life of an existing structure.”
RMIT University has responded to this need by equipping graduates with specialist knowledge in this area. The Master of Engineering (Structures and Forensics) is currently the only program of its kind in Australia and one of only a handful in the world.
Throughout the one-year program, students work on real-life examples and there is a research component which is aligned to a real-world industry situation.
“Most structural engineering design methods and code provisions are formulated, usually by building and testing small-scale models in a laboratory environment,” De Silva said.
“However in structural forensics we learn from studying actual engineering failures and reverse engineer to reproduce the structure correctly.”
Jobs for engineers with a qualification in structure and forensics can include acting as an expert witness; an underwriter for an insurance organisation; an asset monitor and manager for a local council or government organisation; a retro-fitter who upgrades old structures with new technologies; a specialist who re-engineers existing structures; or a surveyor and assessor for the heritage listed building sector.
How we respond to our ageing infrastructure is a global issue with potentially devastating ramifications.
On August 1 2007, I-35W Mississippi River Bridge collapsed during peak hour, killing 13 and injuring more than a hundred people.
At the time the media called on De Silva to get his expert opinion.
“During an interview, I said the Mississippi Bridge was too young to collapse, at only 40 years old,” he said.
“I likened it to a young person having a heart attack – most of him is fine but there is one artery that has stopped working.
“There is an understanding that these huge structures are life-like, and when they are ageing, it is similar to if they had a chronic disease – it won’t kill them, but they must be carefully monitored and maintained regularly.”
Story: Rebecca McGillivray