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Stress-free concrete jacking

MATERIALS - Cutting Edge

CRACKING of reinforced concrete structures during lifting or jacking can lead to rebar corrosion and concrete spalling.

Uneven lifting can lead to twisting and torsion loads that the structure is not designed to take.

Even slight differences between jacking points can lead to internal stresses within the concrete even if there is no visual damage to the structure. Normally, controlling and monitoring movement during the lifting process is done manually.

But a system developed by Dutch company Enerpac could mean the end to fears of structural damage during jacking.

The company's Synchronous Lifting System is a computer-controlled combination of digital switching and digital control that ensures the amount of internal stress generated during lifting is limited.

Because structures are not totally homogenous, jacks at the points require different volumes of hydraulic oil and a computer programme controls the flow of this oil by 'switching' or pulsing the flow.

This rapid oil supply rate ensures the system can control the rate of loading and keep individual jack movements smaller than with manual control, reducing the risk of stress.

Before jacking begins, the target value is punched in to the computer which automatically assesses and readjusts the flow of oil to the jacks throughout the lift ensuring they are set within tolerance and the load is aligned exactly.

According to Enerpac the system can dramatically speed up the jacking process, because there is no need to stop after every increment, saving up to 60 per cent of the overall lifting time.