No room for slip-ups on slip joints as infrastructure future shocks pose challenges for building professionals

As urban consolidation concentrates transport infrastructure into closer proximity with social infrastructure and housing, so architects, engineers and builders are seeking to protect builders and occupants long-term against the impact of vibration, cracking and structural weakening.

“Not only are the sort-term impacts of drilling, earthmoving, tunnelling and building presenting ongoing challenges, but also issues such as urban microclimate hot spots and climate change are coming into play,” says Mr David Booty, Manager of bearing manufacturer Hercules Engineering (a division of Cut To Size Plastics).

“This building protection issue goes well beyond reports of new buildings showing faults and cracking, which are alarming enough in themselves. But the potential problem is extending out 10, 20 and 30 years into the future, as buildings have to flexibly withstand more physical impacts from nearby heavy vehicle and machinery activity – and things like hot spots where high-rise and extensive concrete structures are clumped together in particular suburbs and locations. The challenges to build for the future are ongoing and intensifying,” said Mr Booty, whose company is in response fabricating no-maintenance slip joints that combine tough low-friction composite materials with durable metal facings to provide extended lifespan protection against cracking and structural disruption of civil, industrial and resources infrastructure and construction projects.

The latest specially fabricated Herculon™ Composite Slip joints (HSCs) are engineered to last multiple decades, a durability already achieved in service by earlier such bearings in residential, commercial, industrial and resources applications. The HSCs complement existing proven stock and custom types, including Herculon™ structural slip joints, which protect against potentially damaging expansion, contraction, ambient vibration and changing loadings caused by factors such as passing road and rail traffic, production machinery and changing uses of buildings. the latest Some of the latest Herculon™ structural bearings are manufactured by integrating H-Glide fibre-reinforced composite pads sliding on 2B finish stainless steel (pictured right) to achieve an exceptionally low sliding coefficient of friction compared with other engineering bearing materials, even underwater.

Unlike metal bearings that may rust or require continual lubrication and maintenance, the environmentally safe yet hard-wearing H-Glide bearing pads are dry sliding and will not release contaminants into surrounding environments or adjacent processes, says Mr Booty.

HSC slip joints, meanwhile, are located between walls, corbels, beams and concrete floors to provide industrial and commercial engineers, architects and building specifiers with alternatives to more costly types of bearings, or those with shorter lifespans.

The HSC’s Stainless-Steel Plate (2b Finish) and elastomeric pad slip joint structure typically outlasts standard grease-type slip joints multiple times, providing extended lifespan protection for major infrastructure, industrial and mining projects where no-maintenance durability is vital. The slip joints have been proven in service over lifespans of decades, says Mr Booty.

The latest applications of custom engineered HSCs involve diverse projects, including a high-rise residential/commercial project in Sydney, a town centre mixed-use project in Melbourne, and an underground infrastructure project in which core filled block walls incorporated locating dowels to lock the slab in position and allow for expansion, rotation and shock absorption after the slab is cured, said Mr Booty.

“The challenge involved in ensuring the ongoing slip joint protection required for the project was that cutting or drilling stock slip joints to fit around or between the dowels would have compromised their extremely long-life performance, which was one of their major advantages for the job.”

“So, in this case, the solution was custom-engineering HSC slip joints to fit in continuous strips either side of the locating dowels so it could be used in extended lengths to provide optimum load-bearing capacity and reliability in a restricted space,” says Mr Booty.

This configuration also obtained the greatest benefit from the ability of the extended slip joint to accommodate small variations in the surfaces of the slab and wall structure, with the 7mm thick slip joint acting to accommodate these variations and spread the load evenly to further contribute to greater reliability and lifespan.

Custom-fabricated Hercules HSC composite slip joint engineered for outstanding durability and lifespan in applications involving filled block walls with dowel locaters for the floor slabs they support.

The custom design obviated the need to drill the Grease Slip joints or to painstakingly and precisely measure the distances between the dowels to use increments of HSC Slip joints. Using the full length of HSC slip joints on both sides of dowels saves significant amounts of installation time.

Challenge and Solution

“Apart from immediate efficiencies and savings, the longer-term benefit is of maximum relevance to architectural, engineering and construction audiences. In the face of an increasingly tighter regulatory environment, professional groups are looking further down the road to see how they can provide assurances of long-term performance to their customers, who are very much aware of the issues,” said Mr Booty.

“Sometimes it is not so much that old methods of countering building movement or inflexibility were wrong in the context of the time they were used, but rather that the bar of durability and efficiency has been raised in the face of new challenges. Increasingly, we are being called upon to design for very long-term horizons,” says Mr Booty.

Hercules Engineering provides a technical brochure (see here) to assist in specifying technologies such as Hercuslip joints and complementary Herculon ranges of structural bearings. This is complemented by customized quotations on broader bearing types and special-purpose products including Laminated Elastomeric, Spherical, Pot Type Bearings and customer engineered solutions.

The technical brochure includes recommended slip joint solutions for optimum cost-efficiency and durability for buildings ranging from hospitals and shopping centres, carparks, transport terminals, office towers and warehouses through to factories, storage tanks, silos, boilers and industrial and resources plant such as pipelines, conveyors, pressure vessels and processing facilities across a diverse range of industry. Included is advice for technologies required for different types of structures located across areas of widely differing climatic and geographic diversity. Hercules Engineering products have been used in landmark projects globally where durability is required, ranging from high-load walkways on the Sydney Opera House, to applications including the Australian Parliament, corporate headquarters in Hong Kong and mines in the Asia-Pacific, Australia and Africa.

Hercules Engineering and Cut To Size Plastics provide a wealth of experience and application guidance, based on almost 50 years of operation in Australasian and Asia-Pacific regions in applying engineering polymer technology to construction, infrastructure, energy, mining, manufacturing, maritime, oil and gas, food and beverage, safety and water and wastewater applications.

Hercules Engineering’s latest example of bearings incorporate incompressible H-Glide sliding layers, which can withstand extreme point pressures of 350-500 megapascals, depending on bearing design and application,” says Mr Booty.

“This outstanding performance – which is up to 40 times greater than conventional water-resistant and non-lubricated fibre-reinforced elastomeric bearing pads – is complemented by the material’s ability to function well in a variety of environments including, but not limited to, damp or underwater applications.

“As tunnelling, foundation and construction changes continue to change and intensify, so also is the range of solutions presented by composite slip joints engineered to provide better performance for longer than ever before.”