Smaller bridge construction and maintenance can benefit from cost-efficient Herculon type D sliding bearings in capacities up to 60 tons per bearing.
A challenge facing builders and operators of thousands of smaller bridges throughout Australasia is ensuring such structures can flexibly and cost-efficiently cope with internal movement and stresses caused by changing loads, vibration, thermal expansion and other common attritional factors.
The ability to provide cost-efficient and maintenance-free solutions to such issues is especially important to road and pedestrian access projects demanding high safety, such as those undertaken in metropolitan infrastructure projects, including health and carpark facilities.
Such capabilities are also important in remote area service vehicle and pedestrian access facilities, such as those providing supply, exploration and service routes to mining and energy and oil and gas projects, where movement within access structures is caused by factors such as climate, changing uses and delivery of plant including conveyors, motors, turbines and reticulation systems.
“Low maintenance is equally important also to government authorities as they face demands from local businesses to refurbish and renew private and public regional infrastructure,” says Mr David Booty, Manager, Hercules Engineering (a division of Cut To Size Plastics).
“It is estimated* that there are more 30,000 timber and concrete bridges maintained by local authorities, for example, of which more than a quarter are in poor or fair condition,” *Source: National State of the Assets Survey 2015.
Many of these are smaller road bridges or pedestrian walkways or bridges and could benefit from a no-maintenance, cost-efficient solution provided by Hercules Engineering through its range of Herculon Type D Bearings (HLD/SG, HLD/FF & HLD/FX), which are widely proven on applications ranging from steel and concrete beam engineering structures through to materials handling and processing facilities.
Herculon HLD Bearings are part of a comprehensive range of Hercules composite slip joints and structural bearings incorporating engineered high performance combinations of engineered thermoplastics and stainless steel facing surfaces.
They are engineered to minimise downtime and maintenance by accommodating the vertical and horizontal stresses imposed by the shuddering and vibration of varying loads.
“Among the big plusses of HLD Bearings, compared with more sophisticated and expensive heavy alternatives such as pot bearings and roller bearings, 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.”
Herculon type D sliding bearings – incorporating polymers proven globally for outstanding durability without lubrication or maintenance – were developed to fulfil the need for low-friction bearings on corbels and columns where continuous slip joints were not appropriate.
Type D Herculon Bearings (HLD/SG) are designed to accept a lateral load of 30 per cent of the vertical rated load, which can be up to 600 kN per bearing in stock sizes, with higher capacity available custom-engineered for particular applications. They are removable and replaceable, to optimise no-maintenance performance in access infrastructure and high output plant such as mineral processing and oil, gas and energy infrastructure and conveyors in applications extending from ports to power plants.
Performance characteristics include
- Outstanding stick-slip performance, to provide smooth, easy movement under load
- Friction co-efficient 0.05 – 0.08 depending on stress
- Expansion capacity up to ± 40mm for standard Bearings. (Larger movements can be accommodated upon request)
- Maximum contact stress 10-12 MPa
- Maximum rotation up to 0.02 radians
- Maximum temperature 80 deg C (with higher temperatures accommodated by thermally insulating bearings or using high temperature materials, both as recommended by Hercules).