22 Feb 2021

Brisbane’s heritage bridges a blessing and a burden

Bearing the brunt of Brisbane’s congestion, bridges form a critical part of the river city’s infrastructure – but they come with their own set of challenges.

While some, such as the Story and Victoria bridges, are familiar sights to any Brisbane resident, there are hundreds of smaller, lesser-known bridges – many that are just as old, or older – criss-crossing the city.

Each offers its own insights into the city’s changing streetscape, architectural history, and council plans for the growing suburbs.

Stuart Rothwell from Engineers Australia’s Queensland Heritage Committee said some bridges, such as the Abbotsford Road Bridge in Albion, were not listed on the state register when they should be.

Mr Rothwell said early bridges around Brisbane and Queensland were built from timber and steel, with the Department of Main Roads still managing several hundred timber bridges across the state.

Many of the bridges stand as examples of varied architectural styles over the decades, ranging from early steel structures, such as Indooroopilly’s Albert railway bridge, built in 1895, to more modern pre-cast concrete structures.

“As bridges get frozen in time, it’s difficult to reproduce them in another era because people just aren’t building bridges like that any more,” Mr Rothwell said.

He said many of Brisbane’s smaller bridges were on roads that were not designed to be arterial corridors but over the years had become key routes through the city.

The heritage-listed Canning Bridge on Lytton Road in Norman Park is one such example. The graceful reinforced concrete bridge spanning Norman Creek now carries thousands of vehicles to and from Brisbane’s eastern suburbs.

Built in the 1900s and added to Brisbane City Council’s local heritage place list in 2002, the structure is a “rare example of an intact concrete bridge” from the 1950s.

But while Canning Bridge’s heritage is important to the city, its location has given council headaches as it tries to manage growing congestion.

The latest road-widening project for the Lytton and Wynnum Road corridor, completed in 2020, hit a bottleneck at the bridge, which couldn’t be widened or altered further.

The Abbotsford Road Bridge, built 30 years earlier in 1928, is another example of an important heritage crossing.

At the time, the introduction of motor vehicles was increasing traffic on Brisbane’s roads, particularly in the rapidly growing suburb of Albion.

The triple-span bridge, built by Walter Taylor and other council officers almost 100 years ago, may be the city’s first reinforced concrete bridge.

Brisbane City Council gave it an extensive overhaul in the 1980s as more and more vehicles rattled over it daily.

The advent of reinforced concrete changed bridge construction significantly in the 1920s and ’30s, enabling engineers to create elegant structures with graceful curves and lines, particularly for short-span bridges over smaller creeks.

“By the early 1960s, pre-stressed concrete had come into play and a lot of those short spans were then pre-cast off-site,” Mr Rothwell said.

“In the 1960s, architectural trends had also changed. People wanted everything to be sleek and simple. Lots of straight lines, a more modern style coming in, and ... a utilitarian factor had come in.”

Council’s infrastructure committee chairman, David McLachlan, said the city’s heritage bridges “reflect our history, form part of our cultural tapestry, and are popular places for people to visit and connect with the past”.

“There are always challenges when it comes to conserving heritage structures, and these include sourcing bespoke materials that are often no longer available in the market, finding the expertise to retrofit and carefully maintain the structure, and obtaining heritage exemption to use modern, more durable bridge materials,” Cr McLachlan said.

Heritage listings mean council often has to seek exemption certificates or lodge development applications to manage any repairs and upgrades, particularly if the material from which a bridge was made is no longer available or isn’t suitable, such as timber.

Mr Rothwell said, ideally, bridges were designed to last for a century, but would still need maintenance during that time.

“They’re hardly going to last 100 years without some sort of intervention to maintain them at some stage,” he said.

“So if you’re looking at a road that has suddenly become congested beyond the capacity of the bridge ... it may be 50 to 60 years old.

“Then someone has two decisions to make: how much is it going to cost to bring this [bridge] back to its original life or condition … and then how are we going to widen it.”

While a bridge like the Canning on Lytton Road has caused headaches for engineers, Mr Rothwell said there were options to preserve such structures – such as removing footpaths to make room for another traffic lane, then building a separate foot bridge beside it.

Alternatively, authorities might resume land and build a second bridge beside the first, putting inward-bound traffic on one bridge and outward on the other.

But other challenges will still linger, such as the sheer weight of modern vehicles rumbling over bridges not designed to bear so much weight.

Even with such challenges, buried under the roads, Brisbane’s heritage bridges offer glimpses into the city’s history and growth throughout the years.

“I like to think some of these bridges actually mark a period of development in our city, therefore if we lose them, we lose that connection with the past,” Mr Rothwell said.

“We should go out of our way if we can [to save them].”

SOURCE: https://www.brisbanetimes.com.au/national/queensland/brisbane-s-heritage-bridges-a-blessing-and-a-burden-20210122-p56w4y.html

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