ANALYSIS

Spending boost presents upgrade opportunity for bridges

All bridges have finite lifespans. Many are now carrying greater loads than they bonded to a mild steel or grade 316 stainless steel were ever expected to, and bearing maintenance is important to longevity base plate. “Among the big plusses of HLD Bearings, compared Government infrastructure spending boosts and cooling expansion and contraction in a bridge with more sophisticated and expensive heavy following the Covid pandemic may provide a welcome structure have to be planned into structures decades alternatives such as pot bearings and roller bearings, opportunity to upgrade many of Australasia’s 57,000-plus bridges, many now handling loads they were not originally expected to carry. The opportunity for maintenance is particularly significant for Australasia’s local roads network, involving some 30,000 bridges in Australia, most small to medium, many built before 1950, and some before the turn of the century. It is also significant for the 4200 bridges on State And Federal Highway networks, including the 4200 for which the NZ Department of Transport is responsible, including 185 of which are single lane and the oldest of which, the Waianakarua South River Bridge, in ahead. All bridges are an expensive asset with a finite lifespan, so it is common sense and safety planning to factor in the foreseeable,” says Mr Booty, who is Manager of Hercules Engineering (a division of Cut To Size Plastics). The challenge facing builders and operators of thousands of smaller bridges and aqueducts throughout Australasia is ensuring how concrete and steel structures can flexibly, quickly, and cost-efficiently cope with internal movement and stresses caused by changing loads, vibration, thermal expansion, and other common attritional factors. are benefits such as lower initial cost, easier installation and no maintenance for periods of 30 years or more,” says Mr Booty. “Larger bridge structures demand sophisticated and typically more expensive solutions, but HLD bearings are very suitable for a wide range of bridge, materials handling, and process equipment structures up to 60 tons per bearing.” The evolving range of Herculon type D sliding bearings – incorporating polymers proven globally for outstanding durability without lubrication or maintenance – were developed to fulfil the need for North Otago, which was built in 1868. low-friction bearings on corbels and columns where continuous sliding joints were not appropriate. “Public authorities who manage most of these typically smaller bridges have long been aware of Aqueducts also are expensive assets, and they can the problem facing our road transport infrastructure, have their foundations weakened if bearings fail in but haven’t had the funds to do the work they would their job of protecting against thermal expansion like to. Now they have the opportunity to list their and contraction and load changes preferred projects with the Government so as to extend the safety and lifespan of assets,” says bridge No-maintenance performance sliding bearing producer Mr David Booty. Stock Type D Herculon Bearings (HLD/SG) are designed to accept a lateral load of 30 per cent of the vertical Mr Booty has more than 40 years’ experience in the rated load, which can be up assessment and life-extending to 600 kN per bearing in stock renovation of bearings sizes, with higher capacity supporting public and private available custom-engineered concrete and steel bridges and accessways, accommodating for particular applications. changing loads and demands They are removable and upon them. replaceable, to optimise He says the engineers responsible for bridge management would often like no-maintenance performance in access infrastructure and high output industrial plant. to do such work for safety and The ability to provide productivity reasons, knowing cost-efficient and that trucks and utility vehicles maintenance-free solutions of all types today are a vital to such issues is especially link in our rural and urban important to road and infrastructure. pedestrian access projects Herculon Type D bearings demanding high safety. are engineered to minimise In addition to public bridges downtime and maintenance handling road transport, such by accommodating the vertical structures include private and horizontal stresses imposed When these cars and trucks were on the roads of Australasia in the 1950s, loads on bridges assets, such as those providing by the shuddering and vibration of were lighter because vehicles – especially trucks- generally were smaller and lighter. supply, exploration and service varying loads routes to mining, energy, oil and “But many of the larger trucks out gas projects, where movement there today weigh far more than within access structures is caused the 30-odd tons that was considered appropriate One solution developed by Hercules Engineering by factors such as climate, changing uses and delivery for short-to-medium bridges up until the mid-70s. comprises the range of no-maintenance, of plant including conveyors, motors, turbines and And not only are all vehicles generally heavier – cars, cost-efficient Herculon Type D Bearings (HLD/ reticulation systems. utes and trucks – but also the number of individual SG, HLD/FF & HLD/FX), which are widely proven Asset life-extending maintenance solutions are also vehicles on the roads has increased vastly since then. on applications ranging from steel and concrete important to access facilities in urban infrastructure “This adds considerably to the changing loads and vibration resulting from generally bigger vehicles beam engineering structures through to materials handling and processing facilities. projects, including pedestrian walkways, small bridges and health and carpark facilities. and more of them.” Herculon Type D Bearings (HLD/SG) consist of a Herculon HLD bearings are part of a comprehensive mild steel or 316 stainless steel top plate to which range of Hercules composite sliding joints and Climate change a polished stainless steel facing plate is fixed. This structural bearings incorporating engineered “Now, climate change also has to be factored into plate slides against a low friction hard-wearing high performance combinations of engineered sliding bearing design, because the rates of heat (PTFE) Hercuflon-coated Hercupad, which is in turn thermoplastics and stainless steel facing surfaces.