Civiltec’s innovative dam sandwich

The dam is the first in the world to feature a composite stainless steel and concrete wall construction as part of the Hydroplus fusegate spillway control retrofit project.Civiltec fabricated the composite walls for the fusegate’s buckets off-site in a fabrication yard, using a purpose-developed connection system.The company recommended the stainless steel/concrete composite construction – rather than the more usual concrete walls – to meet the cost-saving and environmental targets of the client, SA Water.The water authority wanted the fusegates to have a 100-year maintenance-free life – a requirement that Civiltec met by choosing a duplex stainless steel for the structural elements.A recent arrival on the market, LDX2101, offers similar corrosion resistance to 316 grade stainless steel, at a much lower price point, Civiltec says.The composite wall panels were fabricated from 4mm stainless steel plates welded to a lattice-work of ribbing.The two steel panels then connect to form a 150mm “sandwich” – the ribbing of each joined internally by a new, patented system of locking bars designed by Civiltec.Onsite, the main wall elements were welded together and the “sandwich” filled with a low-shrinkage self-compacting concrete, achieving a high level of strength and durability.Civiltec managing director Alan Moss said the composite wall construction worked like a bridge truss, transferring the large hydrostatic loads in a highly efficient way.“A critical element determining the strength of the composite wall is the ability to transfer the bending moments from the one steel shell through the concrete core to the other steel shell,” he said.Civiltec says the off-site fabrication system reduced the amount of time required onsite at Little Para, from eight months to just six weeks.“Less time onsite also reduced site administration overheads and running costs,” Moss said.“Furthermore, the extremely efficient design used far less construction material than is normally required for a project of this nature.“The composite design reduced the amount of stainless steel required by approximately 40 per cent – when compared with a traditional single-plate design.”

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